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Longan (Dimocarpus longan Lour.) is an important tropical and subtropical fruit, and most of its cultivars bloom once a year (once-flowering, OF). Dimocarpus longan cv. 'Sijimi' (SJ) is a tropical ecotype variety that blooms several times a year (continuous-flowering, CF) without the need for low-temperature induction. Several studies have focused on the mechanism of continuous flowering in SJ longan; however, none used leaves as research material. As leaves are a key organ in sensing floral-induction signals, we compared gene-expression differences between mature leaves of CF (SJ) and OF (D. longan cv. 'Shixia' (SX) and D. longan cv. 'Chuliang' (CL)) longan by transcriptome sequencing. An average of 47,982,637, 43,833,340 and 54,441,291 clean reads were obtained for SJ, SX and CL respectively, and a total of 6745 differentially expressed genes (DEGs) were detected. Following Metabolic pathways, Plant-pathogen interaction and Biosynthesis of secondary metabolites, most of the other genes were assigned to the KEGG classifications of MAPK signaling pathway- plant, Plant hormone signal transduction, Amino sugar and nucleotide sugar metabolism and Starch and sucrose metabolism. WGCNA analysis clustered genes into 27 modules, among which bisque4 and darkorange2 module genes specifically were expressed at low and high levels in SJ, respectively. Different gene-expression patterns were detected between CF and OF longan in bisque4 and darkorange2 modules, especially the high levels of transcription factor (TF) expression and the large number of gibberellic acid (GA)-signaling-pathway-specific genes expressed at high levels in CF longan (SJ). Floral-induction-gene expression levels in CF longan, such as levels of GA-signaling-related and FT genes, were always high. In CF longan, after vegetative-growth accumulation, flowers could be directly induced, thereby eliminating the need for low-temperature induction. [ABSTRACT FROM AUTHOR]

The basic leucine zip (bZIP) transcription factors (TFs) are a group of highly conserved gene families that play important roles in plant growth and resistance to adversity stress. However, studies on hormonal regulatory pathways and functional analysis during somatic embryogenesis (SE) in Dimocarpus longan is still unavailable. In this study, a total of 51 bZIP family members were systematically identified in the whole genome of longan, a comprehensive bioinformatics analysis of DlbZIP (bZIP family members of D. longan) was performed, and subcellular localization and profiles patterns after transiently transformed DlbZIP60 were analyzed. The combined analysis of RNA-seq, ATAC-seq and ChIP-seq showed that four members have different H3K4me1 binding peaks in early SE and differentially expressed with increased chromatin accessibility. Comparative transcriptome analysis of bZIPs expression in early SE, different tissues and under 2,4-D treatment revealed that DlbZIP family might involved in growth and development during longan early SE. The qRT-PCR results implied that DlbZIP family were subjected to multiple hormonal responses and showed different degrees of up-regulated expression under indole-3-acetic acid (IAA), abscisic acid (ABA) and methyl jasmonate (MeJA) treatments, which indicated that they played an important role in the hormone synthesis pathways associated with the early SE of longan. Subcellular localization showed that DlbZIP60 was located in the nucleus, and the contents of endogenous IAA, MeJA and ABA were up-regulated in transiently DlbZIP60 overexpressed cell lines. These results suggest that DlbZIP60 may mediate hormones pathways that functions the development during early SE in longan. [ABSTRACT FROM AUTHOR]

B3 family transcription factors play an essential regulatory role in plant growth and development processes. This study performed a comprehensive analysis of the B3 family transcription factor in longan (Dimocarpus longan Lour.), and a total of 75 DlB3 genes were identified. DlB3 genes were unevenly distributed on the 15 chromosomes of longan. Based on the protein domain similarities and functional diversities, the DlB3 family was further clustered into four subgroups (ARF, RAV, LAV, and REM). Bioinformatics and comparative analyses of B3 superfamily expression were conducted in different light and with different temperatures and tissues, and early somatic embryogenesis (SE) revealed its specific expression profile and potential biological functions during longan early SE. The qRT-PCR results indicated that DlB3 family members played a crucial role in longan SE and zygotic embryo development. Exogenous treatments of 2,4-D (2,4-dichlorophenoxyacetic acid), NPA (N-1-naphthylphthalamic acid), and PP333 (paclobutrazol) could significantly inhibit the expression of the DlB3 family. Supplementary ABA (abscisic acid), IAA (indole-3-acetic acid), and GA3 (gibberellin) suppressed the expressions of DlLEC2, DlARF16, DlTEM1, DlVAL2, and DlREM40, but DlFUS3, DlARF5, and DlREM9 showed an opposite trend. Furthermore, subcellular localization indicated that DlLEC2 and DlFUS3 were located in the nucleus, suggesting that they played a role in the nucleus. Therefore, DlB3s might be involved in complex plant hormone signal transduction pathways during longan SE and zygotic embryo development. [ABSTRACT FROM AUTHOR]

Longan (Dimocarpus longan Lour.) is an important tropical and subtropical fruit, and most of its cultivars bloom once a year (once-flowering, OF). Dimocarpus longan cv. ‘Sijimi’ (SJ) is a tropical ecotype variety that blooms several times a year (continuous-flowering, CF) without the need for low-temperature induction. Several studies have focused on the mechanism of continuous flowering in SJ longan; however, none used leaves as research material. As leaves are a key organ in sensing floral-induction signals, we compared gene-expression differences between mature leaves of CF (SJ) and OF (D. longan cv. ‘Shixia’ (SX) and D. longan cv. ‘Chuliang’ (CL)) longan by transcriptome sequencing. An average of 47,982,637, 43,833,340 and 54,441,291 clean reads were obtained for SJ, SX and CL respectively, and a total of 6745 differentially expressed genes (DEGs) were detected. Following Metabolic pathways, Plant-pathogen interaction and Biosynthesis of secondary metabolites, most of the other genes were assigned to the KEGG classifications of MAPK signaling pathway- plant, Plant hormone signal transduction, Amino sugar and nucleotide sugar metabolism and Starch and sucrose metabolism. WGCNA analysis clustered genes into 27 modules, among which bisque4 and darkorange2 module genes specifically were expressed at low and high levels in SJ, respectively. Different gene-expression patterns were detected between CF and OF longan in bisque4 and darkorange2 modules, especially the high levels of transcription factor (TF) expression and the large number of gibberellic acid (GA)-signaling-pathway-specific genes expressed at high levels in CF longan (SJ). Floral-induction-gene expression levels in CF longan, such as levels of GA-signaling-related and FT genes, were always high. In CF longan, after vegetative-growth accumulation, flowers could be directly induced, thereby eliminating the need for low-temperature induction.

Flowering in off-season longan (Dimocarpus longan L.) can be induced effectively by the application of potassium chlorate (KClO3), but the mechanism of the physiological induction is largely unknown to decipher its mechanism and identify genes potentially regulating the process, and comparative analysis via RNA-Seq was performed between vegetative and KClO3-induced floral buds. A total of 18,649 differentially expressed genes (DEGs) were identified between control and treated samples. Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that DEGs related to plant hormone signal transduction, mitogen-activated protein kinase (MAPK) signaling pathway, starch and sucrose metabolism, and phenylpropanoid biosynthesis were enriched in our data. A total of 29 flowering-related DEGs were identified in our study, such as APETALA1 (AP1), APETALA2 (AP2), AUXIN RESPONSE FACTOR 3/ETTIN (ARF3), SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 8 (SPL8), AGAMOUS (AG), and others. The upregulation of AP2 and SPL genes indicates that the age-related pathway is activated and influences the floral induction in KClO3-induced longan floral buds by coordinated regulation of genes related to AP1, AG, and ARF3. This study provides a valuable resource for studying molecular mechanisms underlying chlorate-induced floral transition in off-season longan, which may benefit the development and production of off-season tropical/subtropical fruit trees.

The biosynthesis of nanoparticles has been proposed as a cost-effective and environmentally friendly alternative to chemical and physical methods. In the present study, the synthesis of silver oxide nanoparticles has been achieved using Dimocarpus longan fruit. The fruit extract can act as both the reducing agent and stabilizing agent. The synthesized silver oxide nanoparticles were characterized using UV-visible spectrometer the peak observed at 460 nm, FT-IR spectrum implies that polyphenolic compounds were responsible for the formation of silver oxide nanoparticles, XRD analysis, Scanning Electron microscope (SEM) shows poly dispersed nanoparticles and EDAX spectrum shows sharp peak at 3 KeV. The particle size range was found to be 30 to 123 nm and the stability calculated by Zeta potential was −25 mV. The prepared silver oxide nanoparticles were investigated for their catalytic activity on the reduction of p-nitrophenol(4-NP) to p-aminophenol(4-AP). The fruit extract of silver oxide nanoparticles was biologically active and exhibit antifungal activity. The antioxidant potential of silver oxide nanoparticles were investigated by DPPH assay and the IC50 value was found to be 60 μgml−1. The anticancer activity of silver oxide nanoparticles was determined using MTT assay against MCF-7 breast cancer cells. [ABSTRACT FROM AUTHOR]

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Hydroethanolic longan (Dimocarpus longan Lour.) leaf extract has reported remarkable biological activities related to the aging process for use in cosmeceuticals. Finding the bioactive chemical marker (BCM) could play a crucial role for cosmeceutical manufacturers in guaranteeing the quality of the extract and its efficacy. This study aimed to select the most potential BCM established and predicted for the anti-aging skin of hydroethanolic longan leaf extract. The assessment of anti-aging of the skin was determined by evaluating in vitro antioxidant activities, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and inhibiting lipid peroxidation assay. Furthermore, anti-hyaluronidase and anti-collagenase activity were also determined. The extract underwent bioassay-guided fractionation using normal phase preparative-thin layer chromatography. Ethyl gallate in the fractionated extract possessed biological activities as a high proportion part. The strong positive linear relationship between DPPH scavenging, lipid peroxidation inhibition, anti-collagenase, and anti-hyaluronidase activity (r = 0.997, 0.972, 0.998, and 0.998, respectively) under the deterioration of the ethyl gallate was shown. The molecular docking of ethyl gallate to collagenase and hyaluronidase resulted in a good and acceptable binding affinity. Therefore, ethyl gallate could be potentially used as a bioactive chemical marker for hydroethanolic longan leaf extract in pharmaceutical and cosmeceutical applications.

The basic leucine zip (bZIP) transcription factors (TFs) are a group of highly conserved gene families that play important roles in plant growth and resistance to adversity stress. However, studies on hormonal regulatory pathways and functional analysis during somatic embryogenesis (SE) in Dimocarpus longan is still unavailable. In this study, a total of 51 bZIP family members were systematically identified in the whole genome of longan, a comprehensive bioinformatics analysis of DlbZIP (bZIP family members of D. longan) was performed, and subcellular localization and profiles patterns after transiently transformed DlbZIP60 were analyzed. The combined analysis of RNA-seq, ATAC-seq and ChIP-seq showed that four members have different H3K4me1 binding peaks in early SE and differentially expressed with increased chromatin accessibility. Comparative transcriptome analysis of bZIPs expression in early SE, different tissues and under 2,4-D treatment revealed that DlbZIP family might involved in growth and development during longan early SE. The qRT-PCR results implied that DlbZIP family were subjected to multiple hormonal responses and showed different degrees of up-regulated expression under indole-3-acetic acid (IAA), abscisic acid (ABA) and methyl jasmonate (MeJA) treatments, which indicated that they played an important role in the hormone synthesis pathways associated with the early SE of longan. Subcellular localization showed that DlbZIP60 was located in the nucleus, and the contents of endogenous IAA, MeJA and ABA were up-regulated in transiently DlbZIP60 overexpressed cell lines. These results suggest that DlbZIP60 may mediate hormones pathways that functions the development during early SE in longan.

Abstract Background Dimocarpus longan is a tropical tree that produces edible fruit. It is a neglected plant species that is listed as near threatened. In spite of its economic value, the propagation of longan cultivar using conventional methods is extremely difficult. The goal of this research is to produce and conserve this plant through in vitro propagation. Results In order to form new shoots, sterilized shoot tip explants were cultured on Murashige and Skoog (MS) medium supplemented with benzyl adenine (BA) or 2-isobentenyl-adenine (2ip). For direct organogenesis, young leaves of new shoots were cultured on MS medium fortified with various concentrations of Thidiazuron (TDZ) or 6-(4-Hydroxy-3-methylbut-2-enylamino purine) (Zeatin). Gibbrellic acid (GA3) at different levels alone or in combination was used for shoot elongation. Also, indole-3-butyric acid (IBA) and naphthalene acetic acid (NAA) were used for root formation. MS medium supplemented with 1.00 mg/l 2ip was suitable for inducing axillary shoots from shoot tips (4.0 axillary shoots/explant). The highest significant 76% and numbers of adventitious buds from leaf base were achieved on MS medium containing 1.0 mg/l TDZ. These buds developed into the longest plantlets on GA3 at 3.0 mg/l and rooted well in ½MS containing 1.50 mg/l IBA plus 0.50 mg/l (NAA). About 70% in vitro plants were successfully acclimatized. The AFLP profile illustrated the genetic stability of gene expression action. The amplified fragment length polymorphisms (AFLPs) profile illustrated the progenies were extremely similar to the mother plants. According to our findings, MS medium containing 25 ppm salicylic acid (SA) and 5 ppm methyl jasmonate (MeJA) produced the highest percentage of apigenin in longan calli (77.09 and 2.637%, w/w). Conclusion A successful and efficient micropropagation protocol has been developed and described here for the first time, and it will be very useful for the clonal propagation and conservation of the near-threatened Dimocarpus longan plant. Micropropagated plants are genetically identical to the donor plant using the AFLP technique. The usefulness of salicylic acid and methyl jasmonate as elicitors for increasing in vitro production of secondary metabolites in plants is demonstrated in this work.

[Display omitted] • A total of 6 GAD family members were systematically identified in the whole genome of longan. DlGAD5 is localized in the cytoplasm. • DlGADs are involved in hormone synthesis and signaling for IAA and ABA in longan SE. • The expression of 6 DlGADs was up-regulated after overexpressing DlGAD5. Moreover, the activity of GAD was enhanced. Glutamate decarboxylase (GAD) is involved in GABA metabolism and plays an essential regulatory role in plant growth, abiotic stresses, and hormone response. This study investigated the expression mechanism of the GAD family during longan early somatic embryogenesis (SE) and identified 6 GAD genes based on the longan genome. Homology analysis indicated that DlGAD genes had a closer relationship with dicotyledonous plants. The analysis of cis -acting elements in the promoter region suggests that the GAD genes were associated with various stress responses and hormones. RNA sequencing (RNA-Seq) and the qRT-PCR data indicated that most DlGAD genes were highly expressed in the incomplete compact pro-embryogenic cultures (ICpEC) and upregulated in longan embryogenic callus (EC) after treatments with 2,4-D, high temperature (35 °C), IAA, and ABA. Moreover, the RNA-Seq analysis also revealed that DlGADs exhibit different expression patterns in various tissues and organs. The subcellular localization results showed that DlGAD5 was localized in the cytoplasm, suggesting that it played a role in the cytoplasm. Transient overexpression of DlGAD5 enhanced the expression levels of DlGADs and increased the activity of glutamate decarboxylase in longan embryogenic callus (EC), while the content of glutamic acid decreased. Thus, the DlGAD gene can play an important role in the early somatic embryogenesis of longan by responding to hormones such as IAA and ABA. DlGAD5 can affect the growth and development of longan by stimulating the expression of the DlGAD gene family, thereby increasing the GAD activity in the early SE of longan, participating in hormone synthesis and signaling pathways. [ABSTRACT FROM AUTHOR]

Scented tea has been demonstrated to possess favourable pharmacological properties and exert a range of beneficial effects on human health. Longan flowers (Dimocarpus longan) are rich in nutrients and have a strong aroma; however, to date, no studies have reported the production of scented tea from longan flowers. The present study sought to investigate the impact of varying fixation and drying methods on the nutritional and antioxidant components of longan flowers. The findings indicated that, with the exception of free amino acids, the contents of other components in longan flowers were not affected by the different drying methods. Longan flowers subjected to steam fixation had higher average content of polyphenols and flavonoids, resulting in higher antioxidant and reducing power capacity. Therefore, this study examined the quality of longan scented tea prepared using different fixation and drying methods, promoted further processing of longan scented tea, and provided a reference to comprehensively utilize longan scented tea for benefiting human health. • Steam fixation had minimal impact on the nutritional components of longan flowers. • Steam fixation enhanced the content of antioxidant components and reducing power. • Different drying methods had little impact on longan scented tea process. [ABSTRACT FROM AUTHOR]

Strigolactones (SLs), a new class of plant hormones, are implicated in the regulation of various biological processes. However, the related family members and functions are not identified in longan (Dimocarpus longan Lour.). In this study, 23 genes in the CCD, D27, and SMXL family were identified in the longan genome. The phylogenetic relationships, gene structure, conserved motifs, promoter elements, and transcription factor-binding site predictions were comprehensively analysed. The expression profiles indicated that these genes may play important roles in longan organ development and abiotic stress responses, especially during early somatic embryogenesis (SE). Furthermore, GR24 (synthetic SL analogue) and Tis108 (SL biosynthesis inhibitor) could affect longan early SE by regulating the levels of endogenous IAA (indole-3-acetic acid), JA (jasmonic acid), GA (gibberellin), and ABA (abscisic acid). Overexpression of SMXL6 resulted in inhibition of longan SE by regulating the synthesis of SLs, carotenoids, and IAA levels. This study establishes a foundation for further investigation of SL genes and provides novel insights into their biological functions. [ABSTRACT FROM AUTHOR]

Little is known about the adaptability of lychee (Litchi chinensis) to acidic soils high in aluminum (Al). A 2-year greenhouse study was conducted to determine the effects of various levels of soil Al on dry matter production, plant growth, and nutrient concentration in shoots of lychee cultivar rootstock seedlings (maternal half-sibs) of cultivars Brewster, Bostworth-3 (Kwai May Pink), and Kaimana. Soil Al treatments were statistically different for all variables measured in the study but not rootstock seedlings. Total leaf, stem, and root dry weights significantly decreased at soil Al concentrations ranging from 0.42 to 12.69 cmol·kg−1. Increments in soil Al resulted in a significant reduction in the concentration of leaf calcium and phosphorus and a significant increase in leaf Al in cultivar rootstock seedlings. The concentration of leaf potassium, magnesium, iron, zinc, and boron were in the optimum range for lychee, whereas leaf nitrogen and manganese concentrations were above optimum. The results of this study demonstrated no cultivar rootstock seedlings differences for dry matter production in lychee trees grown under Al stress and demonstrate that lychee is highly susceptible to acid soils.

Background: Dimocarpus longan is a tropical tree that produces edible fruit. It is a neglected plant species that is listed as near threatened. In spite of its economic value, the propagation of longan cultivar using conventional methods is extremely difficult. The goal of this research is to produce and conserve this plant through in vitro propagation. Results: In order to form new shoots, sterilized shoot tip explants were cultured on Murashige and Skoog (MS) medium supplemented with benzyl adenine (BA) or 2-isobentenyl-adenine (2ip). For direct organogenesis, young leaves of new shoots were cultured on MS medium fortified with various concentrations of Thidiazuron (TDZ) or 6-(4-Hydroxy-3-methylbut-2-enylamino purine) (Zeatin). Gibbrellic acid (GA3) at different levels alone or in combination was used for shoot elongation. Also, indole-3-butyric acid (IBA) and naphthalene acetic acid (NAA) were used for root formation. MS medium supplemented with 1.00 mg/l 2ip was suitable for inducing axillary shoots from shoot tips (4.0 axillary shoots/explant). The highest significant 76% and numbers of adventitious buds from leaf base were achieved on MS medium containing 1.0 mg/l TDZ. These buds developed into the longest plantlets on GA3 at 3.0 mg/l and rooted well in ½MS containing 1.50 mg/l IBA plus 0.50 mg/l (NAA). About 70% in vitro plants were successfully acclimatized. The AFLP profile illustrated the genetic stability of gene expression action. The amplified fragment length polymorphisms (AFLPs) profile illustrated the progenies were extremely similar to the mother plants. According to our findings, MS medium containing 25 ppm salicylic acid (SA) and 5 ppm methyl jasmonate (MeJA) produced the highest percentage of apigenin in longan calli (77.09 and 2.637%, w/w). Conclusion: A successful and efficient micropropagation protocol has been developed and described here for the first time, and it will be very useful for the clonal propagation and conservation of the near-threatened Dimocarpus longan plant. Micropropagated plants are genetically identical to the donor plant using the AFLP technique. The usefulness of salicylic acid and methyl jasmonate as elicitors for increasing in vitro production of secondary metabolites in plants is demonstrated in this work. [ABSTRACT FROM AUTHOR]

Sugars will eventually be exported transporters (SWEET), a group of relatively novel sugar transporters, that play important roles in phloem loading, seed and fruit development, pollen development, and stress response in plants. Longan (Dimocarpus longan), a subtropic fruit tree with high economic value, is sensitive to cold. However, whether the SWEET gene family plays a role in conferring cold tolerance upon longan remains unknown. Here, a total of 20 longan SWEET (DlSWEET) genes were identified, and their phylogenetic relationships, gene structures, cis-acting elements, and tissue-specific expression patterns were systematically analyzed. This family is divided into four clades. Gene structures and motifs analyses indicated that the majority of DlSWEETs in each clade shared similar exon–intron organization and conserved motifs. Tissue-specific gene expression suggested diverse possible functions for DlSWEET genes. Cis-elements analysis and quantitative real-time PCR (qRT-PCR) analysis revealed that DlSWEET1 responded to cold stress. Notably, the overexpression of DlSWEET1 improved cold tolerance in transgenic Arabidopsis, suggesting that DlSWEET1 might play a positive role in D. longan's responses to cold stress. Together, these results contribute to a better understanding of SWEET genes, which could serve as a foundation for the further functional identification of these genes. [ABSTRACT FROM AUTHOR]

Flavor deterioration reduces the postharvest quality of longan fruit. As an important plant endogenous environmental responsive hormone, the effects of methyl jasmonate (MeJA) treatment on the sugar metabolism of postharvest longan fruit remains to be elucidated. In present study, fruit treated with 100 μmol L−1 MeJA exhibited higher levels of total soluble solids (TSS), sucrose, and total sugar, while lower levels of glucose and fructose. These results are attributed to the inhibited of activities of acid invertase (AI), neutral invertase (NI), and sucrose synthase-cleavage direction (SS-c) in MeJA-treated longan fruit which promote the decomposition of sucrose into glucose and fructose. Additionally, there was an increase in sucrose synthase-synthesis direction (SS-s) and sucrose phosphate synthase (SPS) activities, facilitating sucrose accumulation. Elevated fructokinase (FRK) and hexokinase (HXK) activities in MeJA-treated longan fruit led to a better utilization of glucose and fructose in the glycolysis pathway, thus providing energy for postharvest longan fruit. Compared to the control fruit, the MeJA treatment up-regulated the transcript levels of SS (DlSS-1, DlSS-2 , and DlSS-3), DlSPS , DlFRK , and DlHXK , while down-regulating the transcript levels of AI (Cell wall acid invertase (DlCWAI) and soluble acid invertase (DlSAI)), and NI (DlNI-2 and DlNI-3). In the SS gene, correlation analysis showed that DlSS-1 mainly contributes to promote the sucrose synthesis. These findings suggest that MeJA treatment could improve the status of sugar by modulating the enzyme activities and the expression of genes associated with sugar metabolism, thereby preserving the flavor quality of longan fruit. • MeJA delayed the decrease of sucrose content in postharvest longan fruit. • DlSS1 mainly contributes to the sucrose synthesis during longan storage. • MeJA enhanced the activities of FRK and HXK to better utilization of glucose and fructose. [ABSTRACT FROM AUTHOR]

Longan (Dimocarpus longan Lour.) is a productive fruit crop with high nutritional and medical value in tropical and subtropical regions. The MYB gene family is one of the most widespread plant transcription factor (TF) families participating in the flowering regulation. However, little is known about the MYB TFs involved in the flowering process in longan and its regulatory network. In this study, a total of 119 DlR2R3-MYB genes were identified in the longan genome and were phylogenetically grouped into 28 subgroups. The groupings were supported by highly conserved gene structures and motif composition of DlR2R3-MYB genes in each subgroup. Collinearity analysis demonstrated that segmental replications played a more crucial role in the expansion of the DlR2R3-MYB gene family compared to tandem duplications, and all tandem/segmental duplication gene pairs have evolved under purifying selection. Interspecies synteny analysis among longan and five representative species implied the occurrence of gene duplication events was one of the reasons contributing to functional differentiation among species. RNA-seq data from various tissues showed DlR2R3-MYB genes displayed tissue-preferential expression patterns. The pathway of flower development was enriched with six DlR2R3-MYB genes. Cis -acting element prediction revealed the putative functions of DlR2R3-MYB genes were related to the plant development, phytohormones, and environmental stresses. Notably, the orthologous counterparts between Arabidopsis and longan R2R3-MYB members tended to play conserved roles in the flowering regulation and stress responses. Transcriptome profiling on off-season flower induction (FI) by KClO3 indicated two up-regulated and four down-regulated DlR2R3-MYB genes involved in the response to KClO3 treatment compared with control groups. Additionally, qRT-PCR confirmed certain genes exhibited high expression in flowers/flower buds. Subcellular localization experiments revealed that three predicted flowering-associated MYB proteins were localized in the nucleus. Future functional studies on these potential candidate genes involved in the flowering development could further the understanding of the flowering regulation mechanism. [ABSTRACT FROM AUTHOR]

Abstract Background Somatic embryogenesis (SE) is a process of somatic cells that dedifferentiate to totipotent embryonic stem cells and generate embryos in vitro. Longan SE has been established and wildly used as model system for studying embryogenesis in woody plants, SE-related genes had been characterized. In spite of that, a comprehensive overview of SE at a molecular level is still absent. To understand the molecular mechanisms during longan SE, we examined the transcriptome changes by using Illumina HiSeq from the four distinct developmental stages, including non-embryogenic callus (NEC), embryogenic callus (EC), incomplete compact pro-embryogenic cultures (ICpEC), globular embryos (GE). Results RNA-seq of the four samples generated a total of 243.78 million high quality reads, approximately 81.5% of the data were mapped to longan genome. The cDNA libraries of NEC, EC, ICpEC and GE, generated 22,743, 19,745, 21,144, 21,102 expressed transcripts, 1935, 1710, 1816, 1732 novel transcripts, 2645, 366, 505, 588 unique genes, respectively. Comparative transcriptome analysis showed that a total of 10,642, 4180, 5846 and 1785 genes were differentially expressed in the pairwise comparisons of NEC_vs_EC, EC_vs_ICpEC, EC_vs_GE, ICpEC_vs_GE, respectively. Among them, plant hormones signalling related genes were significantly enriched, especially the auxin and cytokinin signalling components. The transcripts of flavonoid biosynthesis related genes were mainly expressed in NEC, while fatty acid biosynthesis related genes mainly accumulated in early SE. In addition, the extracelluar protein encoding genes LTP, CHI, GLP, AGP, EP1 were related to longan SE. Combined with the FPKM value of longan nine tissues transcription, 27 SE specific or preferential genes (LEC1, LEC1-like, PDF1.3, GH3.6, AGL80, PIN1, BBM, WOX9, WOX2, ABI3, et al.) and 28 NEC preferential genes (LEA5, CNOT3, DC2.15, PR1–1, NsLTP2, DIR1, PIP1, PIP2.1, TIP2–1, POD-P7 and POD5 et al.) were characterized as molecular markers for longan early SE. qRT-PCR validation of SE-related genes showed a high correlation between RNA-seq and qRT-PCR data. Conclusion This study provides new insights into the role of the transcriptome during early SE in longan. Differentially expressed genes reveal that plant hormones signalling, flavonoid and fatty acid biosynthesis, and extracelluar protein related genes were involved in longan early SE. It could serve as a valuable platform resource for further functional studies addressing embryogenesis in woody plants.

Abstract Background The APETALA2/ethylene responsive factor (AP2/ERF) superfamily members are transcription factors that regulate diverse developmental processes and stress responses in plants. They have been identified in many plants. However, little is known about the AP2/ERF superfamily in longan (Dimocarpus longan Lour.), which is an important tropical/subtropical evergreen fruit tree that produces a variety of bioactive compounds with rich nutritional and medicinal value. We conducted a genome-wide analysis of the AP2/ERF superfamily and its roles in somatic embryogenesis (SE) and developmental processes in longan. Results A genome-wide survey of the AP2/ERF superfamily was carried out to discover its evolution and function in longan. We identified 125 longan AP2/ERF genes and classified them into the ERF (101 members), AP2 (19 members), RAV (four members) families, and one Soloist. The AP2 and Soloist genes contained one to ten introns, whereas 87 genes in the ERF and RAV families had no introns. Hormone signaling molecules such as methyl jasmonate (MeJA), abscisic acid (ABA), gibberellin, auxin, and salicylic acid (SA), and stress response cis-acting element low-temperature (55) and defense (49) boxes also were identified. We detected diverse single nucleotide polymorphisms (SNPs) between the ‘Hong He Zi’ (HHZ) and ‘SI JI MI’ (SJM) cultivars. The number of insertions and deletions (InDels) was far fewer than SNPs. The AP2 family members exhibited more alternative splicing (AS) events in different developmental processes of longan than members of the other families. Expression pattern analysis revealed that some AP2/ERF members regulated early SE and developmental processes in longan seed, root, and flower, and responded to exogenous hormones such as MeJA, SA, and ABA, and 2,4-D, a synthetic auxin. Protein interaction predictions indicated that the Baby Boom (BBM) transcription factor, which was up-regulated at the transcriptional level in early SE, may interact with the LALF/AGL15 network. Conclusions The comprehensive analysis of molecular evolution and expression patterns suggested that the AP2/ERF superfamily may plays an important role in longan, especially in early SE, and in seed, root, flower, and young fruit. This systematic analysis provides a foundation for further functional characterization of the AP2/ERF superfamily with the aim of longan improvement.

Longan (Dimocarpus longan Lour.) is a productive fruit crop with high nutritional and medical value in tropical and subtropical regions. The MYB gene family is one of the most widespread plant transcription factor (TF) families participating in the flowering regulation. However, little is known about the MYB TFs involved in the flowering process in longan and its regulatory network. In this study, a total of 119 DlR2R3-MYB genes were identified in the longan genome and were phylogenetically grouped into 28 subgroups. The groupings were supported by highly conserved gene structures and motif composition of DlR2R3-MYB genes in each subgroup. Collinearity analysis demonstrated that segmental replications played a more crucial role in the expansion of the DlR2R3-MYB gene family compared to tandem duplications, and all tandem/segmental duplication gene pairs have evolved under purifying selection. Interspecies synteny analysis among longan and five representative species implied the occurrence of gene duplication events was one of the reasons contributing to functional differentiation among species. RNA-seq data from various tissues showed DlR2R3-MYB genes displayed tissue-preferential expression patterns. The pathway of flower development was enriched with six DlR2R3-MYB genes. Cis-acting element prediction revealed the putative functions of DlR2R3-MYB genes were related to the plant development, phytohormones, and environmental stresses. Notably, the orthologous counterparts between Arabidopsis and longan R2R3-MYB members tended to play conserved roles in the flowering regulation and stress responses. Transcriptome profiling on off-season flower induction (FI) by KClO3 indicated two up-regulated and four down-regulated DlR2R3-MYB genes involved in the response to KClO3 treatment compared with control groups. Additionally, qRT-PCR confirmed certain genes exhibited high expression in flowers/flower buds. Subcellular localization experiments revealed that three predicted flowering-associated MYB proteins were localized in the nucleus. Future functional studies on these potential candidate genes involved in the flowering development could further the understanding of the flowering regulation mechanism.

The 20% ethanol extract of Polygala tenuifolia, Angelica tenuissima, and Dimocarpus longan (WIN-1001X) was derived from a modified version of Korean traditional herbal formula 'Chungsimyeolda-tang' which has been used for the treatment of cerebrovascular disorders. The Parkinson's disease presents with impaired motor functions and loss of dopaminergic neurons. However, the treatment for Parkinson's disease is not established until now. This study aims to elucidate the therapeutic advantages of WIN-1001X on animal models of Parkinson's disease. WIN-1001X administration successfully relieved the Parkinsonism symptoms in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease mice tested by rota-rod and pole tests. The loss of tyrosine hydroxylase activities in substantia nigra and striatum was also attenuated by administration of WIN-1001X. In mice with sub-chronical MPTP injections, autophagy-related proteins, such as LC3, beclin-1, mTOR, and p62, were measured using the immunoblot assay. The results were favorable to induction of autophagy after the WIN-1001X administration. WIN-1001X treatment on 6-hydroxydopamine-injected rats also exhibited protective effects against striatal neuronal damage and loss of dopaminergic cells. Such protection is expected to be due to the positive regulation of autophagy by administration of WIN-1001X with confirmation both in vivo and in vitro. In addition, an active compound, onjisaponin B was isolated and identified from WIN-1001X. Onjisaponin B also showed significant autophagosome-inducing effect in human neuroblastoma cell line. Our study suggests that relief of Parkinsonism symptoms and rescue of tyrosine hydroxylase activity in dopaminergic neurons are affected by autophagy enhancing effect of WIN-1001X which the onjisaponin B is one of the major components of activity. [ABSTRACT FROM AUTHOR]

Longan (Dimocarpus longan L.) is one of the most important tropical and subtropical fruits in the world. Longan fruit has high nutritional and medical value, and is regarded as a treasure among fruits. Since it was first reported that potassium chlorate (KClO3) could be successfully applied to promote flowering in longan, this compound has been widely used in the production of on-season and off-season longan fruits. KClO3 has thus played a great role in promoting the development of the longan industry. In this review, we summarize the application methods, influencing factors, and physiological and molecular mechanisms associated with KClO3-mediated induction of longan flowering. It can be deduced that leaves may play a crucial role in the transport of and response to KClO3. Leaves supply carbon and nitrogen nutrition, and hormone and signaling molecules needed for the differentiation of apical buds. Moreover, cytokinins may be crucial for KClO3-mediated induction of longan flowering. More effort should be focused on studying the molecular mechanisms underlying this process. This will not only help us to better understand floral induction by KClO3 in longan but also enrich our understanding of flowering regulation mechanisms in woody plants.

Longan (Dimocarpus longan L.) is one of the most important tropical and subtropical fruits in the world. Longan fruit has high nutritional and medical value, and is regarded as a treasure among fruits. Since it was first reported that potassium chlorate (KClO3) could be successfully applied to promote flowering in longan, this compound has been widely used in the production of on-season and off-season longan fruits. KClO3 has thus played a great role in promoting the development of the longan industry. In this review, we summarize the application methods, influencing factors, and physiological and molecular mechanisms associated with KClO3-mediated induction of longan flowering. It can be deduced that leaves may play a crucial role in the transport of and response to KClO3. Leaves supply carbon and nitrogen nutrition, and hormone and signaling molecules needed for the differentiation of apical buds. Moreover, cytokinins may be crucial for KClO3-mediated induction of longan flowering. More effort should be focused on studying the molecular mechanisms underlying this process. This will not only help us to better understand floral induction by KClO3 in longan but also enrich our understanding of flowering regulation mechanisms in woody plants. [ABSTRACT FROM AUTHOR]

DNA methylation plays key roles in regulating genes which control somatic embryogenesis (SE) in plant. 5-Azacytidine (5-AzaC) was considered as a common inhibitor of DNA methylation. Longan (Dimocarpus longan Lour.) SE has been established and used as model system for studying mechanism of SE in woody plants. However, effects of 5-AzaC on longan EC and the underlying mechanism at molecular level are rarely understood. In this study, RNA-seq was performed for transcriptome analysis of longan EC treated with or without 5-AzaC were analysed. A total of 29,232 expressed genes were obtained by aligned to longan reference genome and 1,617 differentially expressed genes (DEGs) were got in the pairwise comparisons of CK_vs_T. Integrating the KEGG enrichment pathway analysis showed that 'butanoate metabolism', 'C5-branched dibasic acid metabolism', 'sulphur metabolism', 'selenocompound metabolism', 'pantothenate and CoA biosynthesis', 'phagosome', and 'plant hormone signal transduction' were significantly enriched pathways, while the analysis of DEGs revealed that 5-AzaC-treatment could alter genes expression which related to the SE to adjust the complicated metabolic pathways. Therefore, these results indicated that 5-AzaC-treatment positively impact the development of early SE from longan and a decrease in the global DNA methylation level during early SE in longan. [ABSTRACT FROM AUTHOR]

To study the function of phytoene synthase gene in carotenoid synthesis of Dimocarpus longan Lour.(D. longan), a DlPSY gene identified from D. longan RNA-seq data was screened and analyzed in this research by bioinformatics methods including the primary structure of protein, physicochemical properties, signal peptide, transmembrane structure, subcellular localization, hydrophilicity, protein secondary structure and tertiary structure, coiled coil, protein binding site, phylogenetic tree, as well as protein-protein interaction. In addition, the real-time quantitative PCR(RT-qPCR)was applied in this research to analyze the expression pattern of DlPSY gene in root and leaf tissues. The bioinformatics software used in this research included NCBI BLAST, DNAMAN, NCBI CD search, Protparam, SignalP 4.1 Server, TMHMM Server, SOSUI, PSORT, ProtScale, SOPMA, COILS, SWISS-MODEL, MolProbity, 3DLigandSite, and STRING. The bioinformatics analysis results were as follows: The length of the DlPSY gene was 1 260 bp, coding for 420 amino acids; the DlPSY protein was predicted to have ‘Isoprenoid Biosyn C1' superfamily structure, contained a signal peptide, did not contain the transmembrane structure, and was a soluble hydrophilic and secretory protein which was predicted to be located outside the membrane; the DlPSY protein secondary structure was predicted to be mainly composed of α-helix and random coil; the DlPSY protein was predicted to have a coiled coil. The Ramachandran evaluation results showed that the tertiary structure model constructed by SWISS-MODEL was reliable, and its ligand binding sites were 344Phe and 347Lys, respectively. In addition, the expression pattern of the DlPSY gene was analyzed by RT-qPCR, the results of which showed that the DlPSY gene was expressed in roots and leaves of D. longan but with the different expression levels. The expression level of DlPSY gene was higher in leaves than that in roots. The results of this study will enrich our knowledge on PSY gene family and also lay a foundation for further improving the carotenoid content in D. longan by genetic methods. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China Agricultural University is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Longan (Dimocarpus longan) is a typical southern subtropical fruit tree species that is sensitive to cold stress. C-repeat binding factors (CBFs), as transcription factors, are crucial components involved in the molecular regulation of the plant response to cold stress. However, the role of CBF homologs in the cold response regulation of longan remains largely unknown. Here, three novel CBF genes, DlCBF1, DlCBF2, and DlCBF3, were cloned from longan. DlCBF1 and DlCBF2 contain an AP2 domain and PKKPAGR and DSAWR CBF signature motifs, while DlCBF3 has mutations within these conserved signature motifs. DlCBF1/2/3 were mainly localized in the nucleus and specifically bound to CRT/DRE cis-elements, resulting in strong transcriptional activation. DlCBF1/2 exhibited tissue expression specificity, and their expression was induced by low temperature, while DlCBF3 had no tissue specificity and barely responded to low temperature. DlCBF1, DlCBF2, and DlCBF3 overexpression in Arabidopsis-enhanced cold tolerance by increasing proline accumulation and reducing reactive oxygen species (ROS) content, accompanied by upregulated expression of cold-responsive genes (AtRD29A, AtCOR15A, AtCOR47, and AtKIN1) in the CBF cold stress response signaling pathway. In conclusion, the biological functions of DlCBF1/2/3 were somewhat conserved, but slow expression of DlCBF1/2 and low expression of DlCBF3 may partly cause the cold sensitivity of longan. Collectively, these results indicated that differences exist in the expression and function of CBF orthologs in the cold-sensitive plant species longan, and these findings may help to improve the understanding of the cold response regulation mechanism and provide important theoretical support for cold-tolerant breeding of longan.

Abstract Background Long non-coding RNAs (lncRNAs) are involved in variable cleavage, transcriptional interference, regulation of DNA methylation and protein modification. However, the regulation of lncRNAs in plant somatic embryos remains unclear. The longan (Dimocarpus longan) somatic embryogenesis (SE) system is a good system for research on longan embryo development. Results In this study, 7643 lncRNAs obtained during early SE in D. longan were identified by high-throughput sequencing, among which 6005 lncRNAs were expressed. Of the expressed lncRNAs, 4790 were found in all samples and 160 were specifically expressed in embryogenic callus (EC), 154 in incomplete embryogenic compact structures (ICpECs), and 376 in globular embryos (GEs). We annotated the 6005 expressed lncRNAs, and 1404 lncRNAs belonged to 506 noncoding RNA (ncRNA) families and 4682 lncRNAs were predicted to target protein-coding genes. The target genes included 5051 cis-regulated target genes (5712 pairs) and 1605 trans-regulated target genes (3618 pairs). KEGG analysis revealed that most of the differentially expressed target genes (mRNAs) of the lncRNAs were enriched in the “plant-pathogen interaction” and “plant hormone signaling” pathways during early longan SE. Real-time quantitative PCR confirmed that 20 selected lncRNAs showed significant differences in expression and that five lncRNAs were related to auxin response factors. Compared with the FPKM expression trends, 16 lncRNA expression trends were the same in qPCR. In lncRNA-miRNA-mRNA relationship prediction, 40 lncRNAs were predicted to function as eTMs for 15 miRNAs and 7 lncRNAs were identified as potential miRNA precursors. In addition, we verified the lncRNA-miRNA-mRNA regulatory relationships by transient expression of miRNAs (miR172a, miR159a.1 and miR398a). Conclusion Analyses of lncRNAs during early longan SE showed that differentially expressed lncRNAs were involved in expression regulation at each SE stage, and may form a regulatory network with miRNAs and mRNAs. These findings provide new insights into lncRNAs and lay a foundation for future functional analysis of lncRNAs during early longan SE.

Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Longan (Dimocarpus longan) is a typical southern subtropical fruit tree species that is sensitive to cold stress. C-repeat binding factors (CBFs), as transcription factors, are crucial components involved in the molecular regulation of the plant response to cold stress. However, the role of CBF homologs in the cold response regulation of longan remains largely unknown. Here, three novel CBF genes, DlCBF1 , DlCBF2 , and DlCBF3 , were cloned from longan. DlCBF1 and DlCBF2 contain an AP2 domain and PKKPAGR and DSAWR CBF signature motifs, while DlCBF3 has mutations within these conserved signature motifs. DlCBF1/2/3 were mainly localized in the nucleus and specifically bound to CRT/DRE cis-elements, resulting in strong transcriptional activation. DlCBF1/2 exhibited tissue expression specificity, and their expression was induced by low temperature, while DlCBF3 had no tissue specificity and barely responded to low temperature. DlCBF1, DlCBF2 , and DlCBF3 overexpression in Arabidopsis-enhanced cold tolerance by increasing proline accumulation and reducing reactive oxygen species (ROS) content, accompanied by upregulated expression of cold-responsive genes (AtRD29A , AtCOR15A , AtCOR47 , and AtKIN1) in the CBF cold stress response signaling pathway. In conclusion, the biological functions of DlCBF1/2/3 were somewhat conserved, but slow expression of DlCBF1 / 2 and low expression of DlCBF3 may partly cause the cold sensitivity of longan. Collectively, these results indicated that differences exist in the expression and function of CBF orthologs in the cold-sensitive plant species longan, and these findings may help to improve the understanding of the cold response regulation mechanism and provide important theoretical support for cold-tolerant breeding of longan. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a neurodegenerative disease characterized by the abnormal assembly of amyloid-β (Aβ) and tau aggregates in the brain. When Aβ and tau proteins misfold, progressive brain cell death, synaptic loss, atrophy, and cognitive decline are observed. Here, we report that the memory-enhancing botanical natural product mixture, HX106N, efficiently inhibits formation of Aβ oligomers and fibrils and aggregation of tau. HX106N is a botanical mixture extract of Dimocarpus longan, Liriope platyphylla, Salvia miltiorrhiza and Gastrodia elata. In previous clinical studies, HX106N showed increased working memory performances of individuals of subjective memory complaints. However, the drug mechanism and responsible ingredients of HX106N has been unclear yet. In this study, we expanded the investigation of the drug mode of action to the single chemical level by identifying four active components of HX106N, among 14 isolated molecules, with significant inhibitory function against Aβ aggregation. We found that salvianolic acids A, B, E and rosmarinic acid, isolated from the botanical mixture, have potency to inhibit the protein misfolding. [ABSTRACT FROM AUTHOR]

MicroRNA166 (miR166) contributes to post-transcriptional regulation by binding the mRNAs of HD-ZIP III genes, which affects plant growth and development. The structural characteristics, expression, and functions of miR166 genes during the early somatic embryogenesis stage in Dimocarpus longan remain unknown. We isolated the transcripts of pri-miR166 S78 with two transcription initiation sites (TSSs) and pri-miR166 S338 with one TSS. These sequences contain potential smORFs and encode different miRNA peptides (miPEPs). Additionally, their promoters contain cis- acting elements responsive to diverse stimuli. The pre-miR166 S78 and pre-miR166 S338 expression levels were up-regulated in response to 2,4-D, abscisic acid, and ethylene. Although the expression patterns induced by hormones were similar, there were differences in the extent of the response, with pre-miR166 S338 more responsive than pre-miR166 S78. Thus, miRNA transcription and maturation are not simply linearly correlated. Moreover, pre-miR166 S78 and pre-miR166 S338 expression levels were down-regulated, whereas ATHB15 (target gene) expression was up-regulated, from the longan embryonic callus to the globular embryo stages. These results are indicative of a negative regulatory relationship between miR166 and ATHB15 during the early somatic embryogenesis stage in longan. At the same stages, miR166a.2-agomir, miR166a.2-antagomir, and miPEP166 S338 increased or decreased the expression of miR166a.2 and ATHB15 , but with no consistent patterns or linear synchronization, from which we've found some reasons for it. • The pri-miR166 contain potential smORF and encode different miPEP. • The transcription of pre-miR166 were much higher than that of mature miR166. • The first study combine RNA oligo and miPEP to explore the functions of mature miR166. [ABSTRACT FROM AUTHOR]

Background: The APETALA2/ethylene responsive factor (AP2/ERF) superfamily members are transcription factors that regulate diverse developmental processes and stress responses in plants. They have been identified in many plants. However, little is known about the AP2/ERF superfamily in longan (Dimocarpus longan Lour.), which is an important tropical/subtropical evergreen fruit tree that produces a variety of bioactive compounds with rich nutritional and medicinal value. We conducted a genome-wide analysis of the AP2/ERF superfamily and its roles in somatic embryogenesis (SE) and developmental processes in longan. Results: A genome-wide survey of the AP2/ERF superfamily was carried out to discover its evolution and function in longan. We identified 125 longan AP2/ERF genes and classified them into the ERF (101 members), AP2 (19 members), RAV (four members) families, and one Soloist. The AP2 and Soloist genes contained one to ten introns, whereas 87 genes in the ERF and RAV families had no introns. Hormone signaling molecules such as methyl jasmonate (MeJA), abscisic acid (ABA), gibberellin, auxin, and salicylic acid (SA), and stress response cis-acting element low-temperature (55) and defense (49) boxes also were identified. We detected diverse single nucleotide polymorphisms (SNPs) between the 'Hong He Zi' (HHZ) and 'SI JI MI' (SJM) cultivars. The number of insertions and deletions (InDels) was far fewer than SNPs. The AP2 family members exhibited more alternative splicing (AS) events in different developmental processes of longan than members of the other families. Expression pattern analysis revealed that some AP2/ERF members regulated early SE and developmental processes in longan seed, root, and flower, and responded to exogenous hormones such as MeJA, SA, and ABA, and 2,4-D, a synthetic auxin. Protein interaction predictions indicated that the Baby Boom (BBM) transcription factor, which was up-regulated at the transcriptional level in early SE, may interact with the LALF/AGL15 network. Conclusions: The comprehensive analysis of molecular evolution and expression patterns suggested that the AP2/ERF superfamily may plays an important role in longan, especially in early SE, and in seed, root, flower, and young fruit. This systematic analysis provides a foundation for further functional characterization of the AP2/ERF superfamily with the aim of longan improvement. [ABSTRACT FROM AUTHOR]

Background: Somatic embryogenesis (SE) is a process of somatic cells that dedifferentiate to totipotent embryonic stem cells and generate embryos in vitro. Longan SE has been established and wildly used as model system for studying embryogenesis in woody plants, SE-related genes had been characterized. In spite of that, a comprehensive overview of SE at a molecular level is still absent. To understand the molecular mechanisms during longan SE, we examined the transcriptome changes by using Illumina HiSeq from the four distinct developmental stages, including non-embryogenic callus (NEC), embryogenic callus (EC), incomplete compact pro-embryogenic cultures (ICpEC), globular embryos (GE). Results: RNA-seq of the four samples generated a total of 243.78 million high quality reads, approximately 81.5% of the data were mapped to longan genome. The cDNA libraries of NEC, EC, ICpEC and GE, generated 22,743, 19,745, 21,144, 21,102 expressed transcripts, 1935, 1710, 1816, 1732 novel transcripts, 2645, 366, 505, 588 unique genes, respectively. Comparative transcriptome analysis showed that a total of 10,642, 4180, 5846 and 1785 genes were differentially expressed in the pairwise comparisons of NEC_vs_EC, EC_vs_ICpEC, EC_vs_GE, ICpEC_vs_GE, respectively. Among them, plant hormones signalling related genes were significantly enriched, especially the auxin and cytokinin signalling components. The transcripts of flavonoid biosynthesis related genes were mainly expressed in NEC, while fatty acid biosynthesis related genes mainly accumulated in early SE. In addition, the extracelluar protein encoding genes LTP, CHI, GLP, AGP, EP1 were related to longan SE. Combined with the FPKM value of longan nine tissues transcription, 27 SE specific or preferential genes (LEC1, LEC1-like, PDF1.3, GH3.6, AGL80, PIN1, BBM, WOX9, WOX2, ABI3, et al.) and 28 NEC preferential genes (LEA5, CNOT3, DC2.15, PR1–1, NsLTP2, DIR1, PIP1, PIP2.1, TIP2–1, POD-P7 and POD5 et al.) were characterized as molecular markers for longan early SE. qRT-PCR validation of SE-related genes showed a high correlation between RNA-seq and qRT-PCR data. Conclusion: This study provides new insights into the role of the transcriptome during early SE in longan. Differentially expressed genes reveal that plant hormones signalling, flavonoid and fatty acid biosynthesis, and extracelluar protein related genes were involved in longan early SE. It could serve as a valuable platform resource for further functional studies addressing embryogenesis in woody plants. [ABSTRACT FROM AUTHOR]

Longan fruit pulp sugar content and sweetness decline after ripening, which affects fruit quality and postharvest storage. Fruit sugar decline research has focused mainly on fruit physiology and biochemistry. To explore the molecular mechanism underlying sugar decline, we conducted transcriptome and metabolome analyses of 'Shixia' longan fruit aril (pulp) tissues at different stages of development. In total, 873 metabolites and 26584 annotated unigenes were identified. Sugar content changes in aril tissues were closely related to gene expression patterns related to starch and sucrose metabolism, such as sucrose phosphate synthase (SPS), invertase (INV), sucrose synthase (SUS), and glucose-6-phosphate isomerase (GPI). Notably, glycolytic pathway gene expression and cellulose and lignin contents increased during the sugar decline stage compared to the sugar accumulation stage. Conversely, sucrose transporter genes, such as DlSWEET2b , DlSWEET10 , and DlSWEET12 , showed the opposite expression pattern, pointing to reduced sucrose transport during sugar decline. These results indicate that longan fruit sugar decline is likely related to an interruption of sugar input (cessation of sucrose transport to the aril) and continued glycolysis and cellulose/lignin biosynthesis. This provides a new way to delay longan fruit sugar decline, by regulating sugar transport instead of inhibiting respiration. • A sudden decrease in sucrose content results in longan sugar receding. • Glycolysis and cellulose and lignin synthesis reduce the sucrose content of longan. • Inhibition of expression of sucrose transporter genes blocks sucrose transport. • Input interruption and continuous consumption of sugar lead to sugar receding. [ABSTRACT FROM AUTHOR]

A large quantity of longan fruits (Dimocarpus longan Lour.) produced annually are processed into many products, one of which is black longan, from which the dried, dark-brown meat has been used medicinally in traditional medicine, while the starch-containing seeds are discarded. In this study, starch samples (BLGSs) were isolated from seeds of black longan fruits prepared using varied conditions. The in vitro digestibility was determined in comparison with those extracted from fresh (FLGS) and dried (DLGS) seeds. Scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy were employed to evaluate the starch properties. The results showed that the yields of FLGS, DLGS, and BLGSs were 20%, 23%, and 16–22% w/w, respectively. SEM images showed starch granules of mixed shapes, with sizes up to 15 µm in all samples. XRD patterns confirmed an A-type crystallinity for FLGS and DLGS, with strong refraction peaks at 2θ = 15°, 17°, 18°, and 23°, while BLGSs also showed detectable peaks at 2θ = 10° and 21°, which suggested V-type structures. Thermal properties corroborated the changes by showing increases in peak gelatinization temperature (Tp) and enthalpy energy (ΔH) in BLGSs. The paste viscosity of BLGSs (5% w/w) decreased by 20–58% from that of FLGS. The FTIR peak ratio at 1045/1022 and 1022/995 cm−1 also indicated an increase in ordered structure in BLGSs compared to FLGS. The significant increase in the amounts of slowly digestible starch (SDS) and resistant starch (RS) in BLGSs compared to FLGS, especially at a prolonged incubation time of 20 (4.2×) and 30 days (4.1×), was proposed to be due to the heat-induced formation of starch inclusion with other components inside the seed during the black longan production process. Thus, black longan seed could be a new source of starch, with increased RS content, for potential use in the food and related industries.

ICE1 (inducer of CBF expression 1) encodes a typical MYC-like basic helix-loop- helix (bHLH) transcription factor that acts as a pivotal component in the cold signalling pathway. In this study, DlICE1 , a novel ICE1-like gene, was isolated from the southern subtropical fruit tree longan (Dimocarpus longan Lour.). DlICE1 encodes a nuclear protein with a highly conserved bHLH domain. DlICE1 expression was slightly upregulated under cold stress. Overexpression of DlICE1 in Arabidopsis conferred enhanced cold tolerance via increased proline content, decreased ion leakage, and reduced malondialdehyde (MDA) and reactive oxygen species (ROS) accumulation. Expression of the ICE1-CBF cold signalling pathway genes, including AtCBF1/2/3 and cold-responsive genes (AtRD29A, AtCOR15A, AtCOR47 and AtKIN1), was also significantly higher in DlICE1 -overexpressing lines than in wild-type (WT) plants under cold stress. In conclusion, these findings indicate that DlICE1 is a member of the bHLH gene family and positively regulates cold tolerance in D. longan. • DlICE1 is a novel longan MYC-type ICE1-like transcription factor. • DlICE1 expression of longan leaves was upregulated under cold stress. • DlICE1 overexpression in Arabidopsis enhanced cold tolerance by regulating physiological parameters and cold response genes. [ABSTRACT FROM AUTHOR]

Hiperlipidemia adalah peningkatan konsentrasi lipid, kecuali HDL, dalam plasma akibat ketidakseimbangan antara asupan dan perombakan lemak. Kolesterol, salah satu variabel lipid yang berpengaruh besar terhadap kadar lipid plasma. Berbagai komplikasi hiperkolesterolemia menyebabkan penyakit ini membutuhkan pengobatan efektif dalam menurunkan kadar kolesterol total. Kelengkeng merupakan tanaman potensial dan mudah tumbuh di daerah panas seperti Indonesia. Ekstrak biji dan kulit kelengkeng mengandung flavonoid, saponin dan tannin yang bekerja sebagai antihiperkolesterol dan antioksidan. Penelitian ini bertujuan untuk menguji efek antihiperkolesterolemia dari ekstrak biji dan kulit kelengkeng. Empat puluh mencit dibagi secara acak dalam 8 kelompok yaitu kontrol negatif, kontrol positif, kelompok P1, P2, P3, P4, P5 dan P6. Semua mencit diinduksi dengan pakan tinggi lemak secara oral setiap hari selama tujuh hari. Setelah tahap induksi, dilakukan pengukuran kadar kolesterol total dengan menggunakan Total Cholesterol Meter. Pada masing-masing kelompok diberi perlakuan CMC Na 0,5%, kolestiramin (0,8 g/kg BB), ekstrak biji Dimocarpus longan (70 mg/kg BB, 35 mg/kg BB, 17,5 mg/kg BB) dan kulit Dimocarpus longan (70 mg/kg BB, 35 mg/kg BB, 17,5 mg/kg BB) secara sonde selama tujuh hari setiap pagi hari. Pada akhir penelitian dilakukan pengukuran kadar kolesterol total kedua. Ekstrak biji dan kulit Dimocarpus longan dosis 70 mg/kg BB dan 35 mg/kg BB, serta kolestiramin dosis 0,8 g/kg BB dapat menurunkan kadar kolesterol total secara signifikan (p< 0.05). Penurunan kadar kolesterol total pada ekstrak biji dan kulit Dimocarpus longan tidak sebaik kolestiramin, tetapi dosis 70 mg/kg BB mempunyai kecenderungan mendekati kolestiramin. Penelitian ini menyimpulkan bahwa ekstrak biji dan kulit Dimocarpus longan mempunyai efek antihiperkolesterol pada mencit.

Longan (Dimocarpus longan Lour.), as a kind of commercial fruit tree in the family Sapindaceae, is widely cultivated in South Asia. In this study, we obtained the complete chloroplast genome sequence of longan using Illumina paired-end sequencing. It has 160,833 bp in length, containing a pair of IR regions (28,428 bp) separated by a small single-copy region (18,270 bp) and a large single-copy region (85,707 bp). The overall GC contents of the chloroplast genome were 37.8%. This circular genome contains 130 annotated genes, including 85 protein-coding genes, 37 tRNAs and 8 rRNAs. The phylogenetic analysis using maximum–likelihood (ML) and neighbour-joining (NJ) method showed that longan has the closest relationship with Litchi chinensis, Sapindus mukorossi and Dodonaea viscosa. This complete chloroplast genomes can be subsequently used for the genetic breeding of this valuable species.

Carbohydrates are nutrients and important signal molecules in higher plants. Sugar transporters (ST) play important role not only in long-distance transport of sugar, but also in sugar accumulations in sink cells. Longan (Dimocarpus longan L.) is one of the most important commercial tropical/subtropical evergreen fruit species in Southeast Asia. In this study, a total of 52 longan sugar transporter (DlST) genes were identified and they were divided into eight clades according to phylogenetic analysis. Out of these 52 DlST genes, many plant hormones (e.g., MeJA and gibberellin), abiotic (e.g., cold and drought), and biotic stress responsive element exist in their promoter region. Gene structure analysis exhibited that each of the clades have closely associated gene architectural features based on similar number or length of exons. The numbers of DlSTs, which exhibited alternative splicing (AS) events, in flower bud is more than that in other tissues. Expression profile analysis revealed that ten DlST members may regulate longan flowerbud differentiation. In silico expression profiles in nine longan organs indicated that some DlST genes were tissue specificity and further qRT-PCR analysis suggested that the transcript level of seven DlSTs (DlINT3, DlpGlcT1, DlpGlcT2, DlPLT4, DlSTP1, DlVGT1 and DlVGT2) was consistent with sugar accumulation in fruit, indicating that they might be involved in sugar accumulations during longan fruit development. Our findings will contribute to a better understanding of sugar transporters in woody plant.

B3 family transcription factors play an essential regulatory role in plant growth and development processes. This study performed a comprehensive analysis of the B3 family transcription factor in longan ( Dimocarpus longan Lour.), and a total of 75 DlB3 genes were identified. DlB3 genes were unevenly distributed on the 15 chromosomes of longan. Based on the protein domain similarities and functional diversities, the DlB3 family was further clustered into four subgroups (ARF, RAV, LAV, and REM). Bioinformatics and comparative analyses of B3 superfamily expression were conducted in different light and with different temperatures and tissues, and early somatic embryogenesis (SE) revealed its specific expression profile and potential biological functions during longan early SE. The qRT-PCR results indicated that DlB3 family members played a crucial role in longan SE and zygotic embryo development. Exogenous treatments of 2,4-D (2,4-dichlorophenoxyacetic acid), NPA (N-1-naphthylphthalamic acid), and PP 333 (paclobutrazol) could significantly inhibit the expression of the DlB3 family. Supplementary ABA (abscisic acid), IAA (indole-3-acetic acid), and GA 3 (gibberellin) suppressed the expressions of DlLEC2 , DlARF16 , DlTEM1 , DlVAL2 , and DlREM40 , but DlFUS3 , DlARF5 , and DlREM9 showed an opposite trend. Furthermore, subcellular localization indicated that DlLEC2 and DlFUS3 were located in the nucleus, suggesting that they played a role in the nucleus. Therefore, DlB3s might be involved in complex plant hormone signal transduction pathways during longan SE and zygotic embryo development.

Background: Long non-coding RNAs (lncRNAs) are involved in variable cleavage, transcriptional interference, regulation of DNA methylation and protein modification. However, the regulation of lncRNAs in plant somatic embryos remains unclear. The longan (Dimocarpus longan) somatic embryogenesis (SE) system is a good system for research on longan embryo development. Results: In this study, 7643 lncRNAs obtained during early SE in D. longan were identified by high-throughput sequencing, among which 6005 lncRNAs were expressed. Of the expressed lncRNAs, 4790 were found in all samples and 160 were specifically expressed in embryogenic callus (EC), 154 in incomplete embryogenic compact structures (ICpECs), and 376 in globular embryos (GEs). We annotated the 6005 expressed lncRNAs, and 1404 lncRNAs belonged to 506 noncoding RNA (ncRNA) families and 4682 lncRNAs were predicted to target protein-coding genes. The target genes included 5051 cis-regulated target genes (5712 pairs) and 1605 trans-regulated target genes (3618 pairs). KEGG analysis revealed that most of the differentially expressed target genes (mRNAs) of the lncRNAs were enriched in the "plant-pathogen interaction" and "plant hormone signaling" pathways during early longan SE. Real-time quantitative PCR confirmed that 20 selected lncRNAs showed significant differences in expression and that five lncRNAs were related to auxin response factors. Compared with the FPKM expression trends, 16 lncRNA expression trends were the same in qPCR. In lncRNA-miRNA-mRNA relationship prediction, 40 lncRNAs were predicted to function as eTMs for 15 miRNAs and 7 lncRNAs were identified as potential miRNA precursors. In addition, we verified the lncRNA-miRNA-mRNA regulatory relationships by transient expression of miRNAs (miR172a, miR159a.1 and miR398a). Conclusion: Analyses of lncRNAs during early longan SE showed that differentially expressed lncRNAs were involved in expression regulation at each SE stage, and may form a regulatory network with miRNAs and mRNAs. These findings provide new insights into lncRNAs and lay a foundation for future functional analysis of lncRNAs during early longan SE. [ABSTRACT FROM AUTHOR]

[Objectives] This study was conducted to analyze the interna causes of flower reversal in Longan (Dimocarpus longan Lour.) trees. [Methods] With flowering trees and flower reversal trees as experimental materials, the variations in sugar and starch in mature leaves, tender leaves, mature branches, twigs and terminal buds after flower forcing were analyzed. [Results] During flowering process, sugar content showed the greatest difference between flowering and flower reversal trees, and the diference was the greatest in mature leaves. Trees with mature leaves having a sugar content above 44. 71 mg/g were found to be more prone to flowering, while those with lea sugar content lower than 27.80 m g g were susceptible to flower reversal. In addition, longan trees with a higher sugar content in tender leaves were not prone to flower reversal. [Conclusions] In future, whether off-season flower forcing can be performed on longan trees could be judged through the detection of tree leaves, which is of great significance to prevention of flower reversal in oof-season longan production. [ABSTRACT FROM AUTHOR]

The antimicrobial activity of wood vinegar from Dimocarpus longan was determined in this study. For this, the antimicrobial activity was evaluated against 14 bacterial and 6 fungal strains using an agar well diffusion assay. It was observed that the longan wood vinegar exhibited antibacterial activity against all bacterial strains tested. However, the wood vinegar only showed an inhibitory activity against one fungus which was the yeast Candida albicans. In addition, a preliminary characterisation of the chemical compositions of the longan wood vinegar was made by gas chromatography-mass spectrometry (GC-MS). A total of 6 chemical compounds were identified, representing ca. 60% of the compositions in the wood vinegar. Three major components including 9-octadecenoic acid (oleic acid, 24.56%), n-hexadecanoic acid (palmitic acid, 24.33%), and tetradecanoic acid (myristic acid, 7.16%), were found in the wood vinegar. [ABSTRACT FROM AUTHOR]

[Display omitted] Hydroethanolic longan (Dimocarpus longan Lour.) leaf extract has reported remarkable biological activities related to the aging process for use in cosmeceuticals. Finding the bioactive chemical marker (BCM) could play a crucial role for cosmeceutical manufacturers in guaranteeing the quality of the extract and its efficacy. This study aimed to select the most potential BCM established and predicted for the anti-aging skin of hydroethanolic longan leaf extract. The assessment of anti-aging of the skin was determined by evaluating in vitro antioxidant activities, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and inhibiting lipid peroxidation assay. Furthermore, anti-hyaluronidase and anti-collagenase activity were also determined. The extract underwent bioassay-guided fractionation using normal phase preparative-thin layer chromatography. Ethyl gallate in the fractionated extract possessed biological activities as a high proportion part. The strong positive linear relationship between DPPH scavenging, lipid peroxidation inhibition, anti-collagenase, and anti-hyaluronidase activity (r = 0.997, 0.972, 0.998, and 0.998, respectively) under the deterioration of the ethyl gallate was shown. The molecular docking of ethyl gallate to collagenase and hyaluronidase resulted in a good and acceptable binding affinity. Therefore, ethyl gallate could be potentially used as a bioactive chemical marker for hydroethanolic longan leaf extract in pharmaceutical and cosmeceutical applications. [ABSTRACT FROM AUTHOR]

[Objective] Neutral invertase was a key enzyme of fruit sucrose metabolism, and cloning neutral invertase gene sequences had a significance for sugar metabolism. [Method]Taken Dimocarpus longan ‘Shixia’ cultivar as tested materials, the whole lengths of its three neutral invertase gene cDNA were cloned and sequenced by RT-PCR and RACE. [Result] Three neutral invertase gene cDNAs named as DlNI-1, DlNI-2 and DlNI-3 , the NCBI numbers were KP769773 , KP769774 and KP769775 , of which the DlNI-1 gene consisted of 2090 bp encoding a polypeptide of 589 amino acids, which had the highest homology with the Manihot esculenta crantz (82 %) through the NCBI blastx; The DlNI-2 gene consists of 2558 bp encoding a polypeptide of 709 amino acids, which had the highest homology with the Citrus Clementina (80 %) through the NCBI blastx; The DlNI-3 gene consists of 2444 bp encoding a polypeptide of 805 amino acids, which had the highest homology with the Citrus clementine (80 %) through the NCBI blastx. Amino acids of three longan neutral invertase gene sequence had 12 highly conservative domain structure and two catalytic residues, it was concluded that the three neutral invertase protein belonged to a class and located in organelles. The expression level of three neutral invertase genes had bigger difference in different tissues, the DlNI-1 and DlNI-2 had the highest expression level in leaves, but the DlNI-3 had the highest expression in pericarp. [Conclusion] Three longan neutral invertase gene were cloned, which would provide references for the investigation of the relation between structure and function of neutral invertase gene. [ABSTRACT FROM AUTHOR]

Redox status in ascorbate-glutathione (ASA-GSH) cycle plays a pivotal role in plant responses to physiological and environmental changes. The change of ASA-GSH redox potential is associate with oxidative stress leading to plant senescence. The present study was aimed to investigate the effects of gaseous ClO 2 on the redox status involved in delaying fruit senescence during storage of harvested longan fruit ( Dimocarpus longan Lour. cv. Daw). Fresh longan fruit were fumigated with 10 mg/L ClO 2 for 10 min, packed into cardboard boxes and stored at room temperature for 7 d. The results show that redox status of the fruit determined by ASA/DHA, GSH/GSSG and NADPH/NADP ratios decreased steadily in ClO 2 untreated control group during storage. On the contrary, those ratios increased immediately after ClO 2 treatment before declining steadily afterwards. The activities of NADPH-generating dehydrogenases including glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, and ASA-GSH cycle enzymes including ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase were upregulated upon the ClO 2 treatment and remained stable for a few days. ClO 2 treatment decreased hydrogen peroxide content and fruit senescence index, including browning and disease symptoms in pericarp during storage. It was concluded that the imbalance of redox status of ASA-GSH cascade involved senescence in ‘Daw’ longan, and ClO 2 could maintain the redox balance, leading to the alleviation and delay fruit senescence. [ABSTRACT FROM AUTHOR]