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The ability to perform aggressive movements, which are called aggressive flights, is important for quadrotors during navigation. However, aggressive quadrotor flights are still a great challenge to practical applications. The existing solutions to aggressive flights heavily rely on a predefined trajectory, which is a time-consuming preprocessing step. To avoid such path planning, we propose a curiosity-driven reinforcement learning method for aggressive flight missions and a similarity-based curiosity module is introduced to speed up the training procedure. A branch structure exploration (BSE) strategy is also applied to guarantee the robustness of the policy and to ensure the policy trained in simulations can be performed in real-world experiments directly. The experimental results in simulations demonstrate that our reinforcement learning algorithm performs well in aggressive flight tasks, speeds up the convergence process and improves the robustness of the policy. Besides, our algorithm shows a satisfactory simulated to real transferability and performs well in real-world experiments.

Kiwifruit (Actinidia spp) is a woody, perennial and deciduous vine. In this genus, there are multiple ploidy levels but the main cultivated cultivars are polyploid. Despite the availability of many genomic resources in kiwifruit, SNP genotyping is still a challenge given these different levels of polyploidy. Recent advances in SNP array technologies have offered a high-throughput genotyping platform for genome-wide DNA polymorphisms. In this study, we developed a high-density SNP genotyping array to facilitate genetic studies and breeding applications in kiwifruit. SNP discovery was performed by genome-wide DNA sequencing of 40 kiwifruit genotypes. The identified SNPs were stringently filtered for sequence quality, predicted conversion performance and distribution over the available Actinidia chinensis genome. A total of 134 729 unique SNPs were put on the array. The array was evaluated by genotyping 400 kiwifruit individuals. We performed a multidimensional scaling analysis to assess the diversity of kiwifruit germplasm, showing that the array was effective to distinguish kiwifruit accessions. Using a tetraploid F1 population, we constructed an integrated linkage map covering 3060.9 cM across 29 linkage groups and performed QTL analysis for the sex locus that has been identified on Linkage Group 3 (LG3) in Actinidia arguta. Finally, our dataset presented evidence of tetrasomic inheritance with partial preferential pairing in A. arguta. In conclusion, we developed and evaluated a 135K SNP genotyping array for kiwifruit. It has the advantage of a comprehensive design that can be an effective tool in genetic studies and breeding applications in this high-value crop.

Fruit plants are severely constrained by salt stress in the soil due to their sessile nature. Ca

PurposeThis work aims to combine the cloud robotics technologies with deep reinforcement learning to build a distributed training architecture and accelerate the learning procedure of autonomous systems. Especially, a distributed training architecture for navigating unmanned aerial vehicles (UAVs) in complicated dynamic environments is proposed.Design/methodology/approachThis study proposes a distributed training architecture named experience-sharing learner-worker (ESLW) for deep reinforcement learning to navigate UAVs in dynamic environments, which is inspired by cloud-based techniques. With the ESLW architecture, multiple worker nodes operating in different environments can generate training data in parallel, and then the learner node trains a policy through the training data collected by the worker nodes. Besides, this study proposes an extended experience replay (EER) strategy to ensure the method can be applied to experience sequences to improve training efficiency. To learn more about dynamic environments, convolutional long short-term memory (ConvLSTM) modules are adopted to extract spatiotemporal information from training sequences.FindingsExperimental results demonstrate that the ESLW architecture and the EER strategy accelerate the convergence speed and the ConvLSTM modules specialize in extract sequential information when navigating UAVs in dynamic environments.Originality/valueInspired by the cloud robotics technologies, this study proposes a distributed ESLW architecture for navigating UAVs in dynamic environments. Besides, the EER strategy is proposed to speed up training processes of experience sequences, and the ConvLSTM modules are added to networks to make full use of the sequential experiences.

Kiwifruit (Actinidia sp.) vines are poorly adapted to waterlogging stress. Actinidia valvata is more tolerant against waterlogging stress than Actinidia deliciosa, and the latter contains some common rootstocks that are frequently used in kiwifruit cultivation. Little is known about the responses of A. valvata genotypes against waterlogging stress and during post-waterlogging recovery. Here, we compared physiological traits of three A. valvata genotypes (KR1, KR3, and KR5) during waterlogging stress and recovery. Kiwifruit vines displayed water loss, a decline in the net photosynthetic rate, and inhibited shoot elongation during waterlogging. These three genotypes could endure long-term waterlogging owing to their unique root system configurations as well as by sustaining carbohydrate reserves in the roots. Feeder roots of KR1 vines were damaged earlier and lost water more quickly than the other genotypes. Under the same stress, KR3 formed adventitious roots more rapidly, while KR5 had an improved ability to control water loss in above-ground tissues. After reoxygenation, growth of vines was partially recovered due to water loss control, photosynthetic recovery, and carbohydrate replenishment. KR3 and KR5 recovered their growth earlier and replenished more carbohydrates than KR1 after re-aeration. During waterlogging, both the relative water content and carbohydrate levels of vines can limit the recovery efficiency after re-aeration. Our results revealed mutual and distinct responses of different A. valvata genotypes during waterlogging stress and recovery and provided more insight into the physiological basis of their adaptation to waterlogging stress.

Cold stress in winter can have a disastrous effect on kiwifruit yield and affect geographical distribution. However, freezing tolerance in Actinidia genotypes remains largely unknown. Here, we report changes in metabolite content and enzyme activity in the shoots of Actinidia genotypes exposed to low-temperature stress (− 5 °C, − 10 °C, − 15 °C, − 20 °C, − 25 °C and − 30 °C). Moreover, the relative electrolyte leakage method was used to evaluate the freezing tolerance of kiwifruit germplasm; 51 genotypes from 16 species of Actinidia were evaluated in total. The data revealed that relative electrolyte leakage, proline (Pro), soluble protein, and catalase (CAT) activity changed with different low temperatures. Results showed that among 16 species, A. kolomikta, A. polygama, and A. arguta had lower LT50 than other species. A. arguta, originating from the northeast of China, exhibited stronger freezing resistance than the ones from other places. There was little difference in freezing tolerance between A. chinensis and A. deliciosa. These findings provide new insights into the freezing tolerance ability and mechanisms of kiwifruit and further contribute to our understanding of the relationship between freezing tolerance and geographic distribution.

Fruit skin color is an important characteristic of fruit quality. The light-mediated regulation on fruit skin coloration in Actinidia arguta remains unclear. To better understand the role of light in fruit skin coloration, we performed bagging treatments in both on-tree and off-tree ‘Hongbaoshixing’, which is a kind of all-red-typed A. arguta cultivar. Non-bagging kiwifruits were used as control. For off-tree fruits, there was no difference between non-bagging and bagging treatments. For on-tree fruits, physiological and molecular changes were investigated during fruit development in non-bagging and bagging treatments. Phenotypic identification and the hue angle measurement showed that the stage of most significant color difference between non-bagging and bagging treatments was 130 days (after full bloom). Determination of five anthocyanin components suggested cyanidin-3-O-galactoside and cyanidin-3-O-xylose-galactoside made a main contribution to the fruit skin coloration. Gene expression profiles and cluster analysis showed AaLDOX and AaUFGT were highly expressed at 130 days and obviously clustered into the same class in non-bagging treatment, respectively. Correlation analysis suggested only AaLDOX expression was significantly correlated with anthocyanin content in non-bagging treatment while no correlation in bagging treatment. Similar results was observed for MYB1 transcription factor. The result of subcellular localization showed that AaLDOX was located in the cytoplasm, indicating AaLDOX is indeed structural gene that encodes leucoanthocyanidin dioxygenase participated in anthocyanin biosynthesis. All results were used to establish a possible working model, showing that light is indispensable for normal fruit skin coloration, and bagging treatment suppresses anthocyanin biosynthesis and accumulation mainly by inhibiting AaMYB1 and AaLDOX expression in A. arguta.

The internode length affects the status of fruiting branches and shapes the vine architecture. MYB TFs (transcription factors) have been widely studied and reported to control many biological processes including secondary metabolism, abiotic stresses, growth and development, etc. However, the roles of MYB TFs in regulating internode length remain poorly understood. Here, we demonstrated that a secondary metabolism-related R2R3-MYB TF AaMYBC1 from Actinidia arguta was involved in the regulation of internode length by combined analysis of transcriptome and metabolome of transgenic tobacco plants. The metabolome analysis of OE (over-expressed tobacco) and WT (wild-typed tobacco) showed that there were a total of 1000 metabolites, 176 of which had significant differences. A key metabolite pme1651 annotated as indole 3-acetic acid belonged to phytohormone that was involved in internode length regulation. The RNA-seq analysis presented 446 differentially expressed genes (DEGs) between OE and WT, 14 of which were common DEGs in KEGG and GO enrichment. Through the combined analysis of metabolome and transcriptome in transgenic and wild-type tobacco, three key genes including two SAUR and a GH3 gene were possibly involved in internode elongation. Finally, a regulatory module was deduced to show the role of AaMYBC1 in internode elongation. Our results proposed a molecular mechanism of AaMYBC1 regulating internode length by mediated auxin signaling, implying the potential role in regulating the vine architecture.

Background Kiwifruit (Actinidia Lindl.) is considered an important fruit species worldwide. Due to its temperate origin, this species is highly vulnerable to freezing injury while under low-temperature stress. To obtain further knowledge of the mechanism underlying freezing tolerance, we carried out a hybrid transcriptome analysis of two A. arguta (Actinidi arguta) genotypes, KL and RB, whose freezing tolerance is high and low, respectively. Both genotypes were subjected to − 25 °C for 0 h, 1 h, and 4 h. Results SMRT (single-molecule real-time) RNA-seq data were assembled using the de novo method, producing 24,306 unigenes with an N50 value of 1834 bp. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of DEGs showed that they were involved in the ‘starch and sucrose metabolism’, the ‘mitogen-activated protein kinase (MAPK) signaling pathway’, the ‘phosphatidylinositol signaling system’, the ‘inositol phosphate metabolism’, and the ‘plant hormone signal transduction’. In particular, for ‘starch and sucrose metabolism’, we identified 3 key genes involved in cellulose degradation, trehalose synthesis, and starch degradation processes. Moreover, the activities of beta-GC (beta-glucosidase), TPS (trehalose-6-phosphate synthase), and BAM (beta-amylase), encoded by the abovementioned 3 key genes, were enhanced by cold stress. Three transcription factors (TFs) belonging to the AP2/ERF, bHLH (basic helix-loop-helix), and MYB families were involved in the low-temperature response. Furthermore, weighted gene coexpression network analysis (WGCNA) indicated that beta-GC, TPS5, and BAM3.1 were the key genes involved in the cold response and were highly coexpressed together with the CBF3, MYC2, and MYB44 genes. Conclusions Cold stress led various changes in kiwifruit, the ‘phosphatidylinositol signaling system’, ‘inositol phosphate metabolism’, ‘MAPK signaling pathway’, ‘plant hormone signal transduction’, and ‘starch and sucrose metabolism’ processes were significantly affected by low temperature. Moreover, starch and sucrose metabolism may be the key pathway for tolerant kiwifruit to resist low temperature damages. These results increase our understanding of the complex mechanisms involved in the freezing tolerance of kiwifruit under cold stress and reveal a series of candidate genes for use in breeding new cultivars with enhanced freezing tolerance.

BackgroundFreezing injury, which is an important abiotic stress in horticultural crops, influences the growth and development and the production area of kiwifruit (ActinidiaLind1). AmongActinidiaspecies,Actinidia argutahas excellent cold resistance, but knowledge relevant to molecular mechanisms is still limited. Understanding the mechanism underlying cold resistance in kiwifruit is important for breeding cold resistance.ResultsIn our study, a population resulting from the cross ofA. arguta‘Ruby-3’ × ‘Kuilv’ male was generated for kiwifruit hardiness study, and 20 cold-tolerant and 20 cold-sensitive populations were selected from 492 populations according to their LT50. Then, we performed bulked segregant RNA-seq combined with single-molecule real-time sequencing to identify differentially expressed genes that provide cold hardiness. We found that the content of soluble sucrose and the activity of β-amylase were higher in the cold-tolerant population than in the cold-sensitive population. Upon − 30 °C low-temperature treatment, 126 differentially expressed genes were identify; the expression of 59 genes was up-regulated and that of 67 genes was down-regulated between the tolerant and sensitive pools, respectively. KEGG pathway analysis showed that the DEGs were primarily related to starch and sucrose metabolism, amino sugar and nucleotide sugar metabolism. Ten major key enzyme-encoding genes and two regulatory genes were up-regulated in the tolerant pool, and regulatory genes of theCBFpathway were found to be differentially expressed. In particular, a14–3-3gene was down-regulated and anEBFgene was up-regulated.To validate the BSR-Seq results, 24 DEGs were assessed via qRT-PCR, and the results were consistent with those obtained by BSR-Seq.ConclusionOur research provides valuable insights into the mechanism related to cold resistance inActinidiaand identified potential genes that are important for cold resistance in kiwifruit.

Beta-amylase (BAM) plays an important role in plant resistance to cold stress. However, the specific role of the BAM gene in freezing tolerance is poorly understood. In this study, we demonstrated that a cold-responsive gene module was involved in the freezing tolerance of kiwifruit. In this module, the expression of AaBAM3.1, which encodes a functional protein, was induced by cold stress. AaBAM3.1-overexpressing kiwifruit lines showed increased freezing tolerance, and the heterologous overexpression of AaBAM3.1 in Arabidopsis thaliana resulted in a similar phenotype. The results of promoter GUS activity and cis-element analyses predicted AaCBF4 to be an upstream transcription factor that could regulate AaBAM3.1 expression. Further investigation of protein-DNA interactions by using yeast one-hybrid, GUS coexpression, and dual luciferase reporter assays confirmed that AaCBF4 directly regulated AaBAM3.1 expression. In addition, the expression of both AaBAM3.1 and AaCBF4 in kiwifruit responded positively to cold stress. Hence, we conclude that the AaCBF-AaBAM module is involved in the positive regulation of the freezing tolerance of kiwifruit.

Kiwifruit bacterial canker, caused by the bacterial pathogen Pseudomonas syringae pv. actinidiae (Psa), is a destructive disease in the kiwifruit industry globally. Consequently, understanding the mechanism of defense against pathogens in kiwifruit could facilitate the development of effective novel protection strategies. The Non-expressor of Pathogenesis-Related genes 1 (NPR1) is a critical component of the salicylic acid (SA)-dependent signaling pathway. Here, a novel kiwifruit NPR1-like gene, designated AeNPR1a, was isolated by using PCR and rapid amplification of cDNA ends techniques. The full-length cDNA consisted of 1952 base pairs with a 1,746-bp open-reading frame encoding a 582 amino acid protein. Homology analysis showed that the AeNPR1a protein is significantly similar to the VvNPR1 of grape. A 2.0 Kb 5'-flanking region of AeNPR1a was isolated, and sequence identification revealed the presence of several putative cis-regulatory elements, including basic elements, defense and stress response elements, and binding sites for WRKY transcription factors. Real-time quantitative PCR results demonstrated that AeNPR1a had different expression patterns in various tissues, and its transcription could be induced by phytohormone treatment and Psa inoculation. The yeast two-hybrid assay revealed that AeNPR1a interacts with AeTGA2. Constitutive expression of AeNPR1a induced the expression of pathogenesis-related gene in transgenic tobacco plants and enhanced tolerance to bacterial pathogens. In addition, AeNPR1a expression could restore basal resistance to Pseudomonas syringae pv. tomato DC3000 (Pst) in Arabidopsis npr1-1 mutant. Our data suggest that AeNPR1a gene is likely to play a pivotal role in defense responses in kiwifruit.

Kiwifruit vines are generally sensitive to waterlogging stress. So far, molecular responses of different kiwifruit genotypes for waterlogging stress are less well-explored. In this study, using RNA-sequencing, we examined transcriptional regulation in the roots of a waterlogging-tolerant genotype KR5 (Actinidia valvata), and a sensitive genotype ‘Hayward’ (Actinidia deliciosa) subjected to 0, 12, 24, and 72 h of waterlogging. Compared with 0 h, transcriptional adjustments of these two genotypes occurred as early as 12 h and became notably pronounced 72 h after waterlogging. Waterlogging stress for 72 h promoted the expression of genes involved in ethylene biosynthesis, sucrose and hexose transport, anaerobic fermentation, nitrate reduction, alanine accumulation, and reactive oxygen scavenging in both genotypes. The differential regulation of genes encoding 9-cis-epoxycarotenoid dioxygenase, phosphoglucomutase, alanine-glyoxylate transaminase, and other enzymes pointed to their diverse strategies upon waterlogging in these two genotypes. In addition, more sucrose and trehalose contents, as well as a higher activity of alcohol dehydrogenase and manganese superoxide dismutases were stimulated in KR5 roots after 72h of waterlogging than that in ‘Hayward’. Overall, our results provided more insights into the molecular basis of the waterlogging response in kiwifruit.

In this paper, several experiments were carried out to study the environmental behavior and influencing factors of glyphosate (PMG) in peach orchard ecosystem. The results of field experiments showed that PMG and its metabolite aminomethylphosphonic acid (AMPA) were detected in peach tree leaves and peach tree fruits, although PMG was only sprayed on the soil. The residues of PMG and AMPA in peach tree leaves were ~0.1 mg/kg and ~0.5 mg/kg and in peach tree fruits were ~0.01 mg/kg and 0.07–0.11 mg/kg, respectively. By conducting a series of laboratory simulation experiments, the environmental factors affecting the degradation of PMG were screened and evaluated. The results showed that PMG metabolized much faster in loess soil than red soil and black soil (with the DT50 of 11.6 days, 62.4 days, and 34.1 days, respectively). By analyzing the basic properties of the soil, we investigated the effects of pH, moisture content, organic matter (exogenous biochar) and ambient temperature using orthogonal experiments, and the results were further confirmed by microbial experiment. The results showed that alkaline conditions (pH = 7.8/9), high water content (25%) and microorganisms could promote the degradation of PMG. Sterile soil environment had a negative impact on the metabolic behavior of PMG to AMPA.

To select resistant germplasm resources and understand the growth and physiological responses of kiwifruit (Actinidia sp.) to drought stress, five species, Actinidia macrosperma (Acma), Actinidia longicarpa (Aclo), Actinidia deliciosa (Acde), Actinidia hemsleyana (Ache), and Actinidia valvata (Acva), were assessed under tissue culture conditions. Rootless seedlings of five species were cultured in a medium containing polyethylene glycol [PEG (formula weight 8000)] to induce drought stress (0%, 5%, 10%, 15%, and 20%). After a 30-day culture, three growth indices [fresh weight (FW), plant height (PLH), and leaf number (LN)] and six physiological indices were determined, and the drought damage index (DDI) was determined. The DDIs of five species increased, and three growth indices decreased with increasing PEG concentrations. The following changes were observed under 20% PEG treatment conditions: superoxide dismutase (SOD) activities increased significantly in Acma, Aclo, and Ache specimens; peroxidase (POX) activities remained stable in Acde, Ache, and Acva specimens; and catalase (CAT) activities increased sharply in Acma and Acva. Furthermore, the results indicated that soluble sugar (SS) content increased slightly in Acma, Aclo, Acde, and Ache but it decreased in Acva specimens. Proline (PRO) content increased significantly in Acma and Acva, and malondialdehyde (MDA) contents tended to increase under drought stress in all five species. Principal component analysis (PCA) results indicated that the order of drought tolerance in the five genotypes examined in this study under tissue culture conditions was as follows: Acma > Acva > Acde > Aclo > Ache. Therefore, we concluded that Acma and Acva are more resilient germplasm resources that represent promising kiwifruit-breeding materials. Furthermore, tolerance to drought stress in these species should be further investigated under orchard conditions.

Study on kiwifruit (Actinidia chinensis and A. deliciosa) color mainly concentrated in green and yellow-fleshed cultivars, less about molecular mechanism of red-fleshed trait formation, rarely in all red-fleshed fruit. Using ‘Tianyuanhong’ and ‘Yongfengyihao’ (‘TY’, a kind of all red-fleshed cultivar, from Actinidia arguta; ‘YF’, a kind of all green-fleshed cultivar, also from Actinidia arguta) as experimental material, we performed RNA-seq to obtain 202,742 unigenes with an average length of 603 bp and N50 of 873 bp via transcriptome data analysis. Of these unigenes, 72,508 (35.76%) were annotated and 997 were assigned to secondary metabolic pathways, of which 104 unigenes were involved in flavonoid and anthocyanin biosynthesis. According to the parameter log2fold-change and p-adjusted, 12 differentially expressed structural genes were selected for performing expression profiles and cluster analysis. Physiological traits including color ration, hue angle, and anthocyanin content were also investigated. From the results, we concluded AaLDOX (genes encoding leucoanthocyanidin dioxygenase) maybe the key gene controlling anthocyanin biosynthesis in flesh of ‘TY’ kiwifruit, which promoted accumulation of anthocyanin, finally leading to the red flesh coloration.

Rootstocks from Actinidia valvata are much more tolerant to waterlogging stress than those from Actinidia deliciosa, which are commonly used in kiwifruit production. To date, the tolerance mechanism of A. valvata rootstocks’ adaptation to waterlogging stress has not been well explored. In this study, the responses of KR5 (A. valvata) and ‘Hayward’ (A. deliciosa) to waterlogging stress were compared. Results showed that KR5 plants performed much better than ‘Hayward’ during waterlogging by exhibiting higher net photosynthetic rates in leaves, more rapid formation of adventitious roots at the base of stems, and less severe damage to the main root system. In addition to morphological adaptations, metabolic responses of roots including sufficient sucrose reserves, modulated adjustment of fermentative enzymes, avoidance of excess lactic acid and ethanol accumulation, and promoted accumulation of total amino acids all possibly rendered KR5 plants more tolerant to waterlogging stress compared to ‘Hayward’ plants. Lysine contents of roots under waterlogging stress were increased in ‘Hayward’ and decreased in KR5 compared with their corresponding controls. Overall, our results revealed the morphological and metabolic adaptations of two kiwifruit rootstocks to waterlogging stress, which may be responsible for their genotypic difference in waterlogging tolerance.

Actinidia arguta ‘Tianyuanhong’ is a new kiwifruit variety with an all-red pericarp and pulp, in contrast to the all-green pulp of A. arguta ‘Yongfengyihao’. Transcriptome profile analysis of fruit color has been reported, however, the metabolic mechanisms producing red flesh remain unknown, and it is unclear why the pulp of ‘Tianyuanhong’ is red rather than green. Herein, we identified differences between the proteomes of two A. arguta cultivars with different fruit color by using iTRAQ-based quantitative proteomic methods during the stage of color change. In total, 2310 differentially abundant proteins were detected between the two cultivars at 70 and 100 days after flowering, and the protein functions were analyzed based on KEGG and GO. The largest group of differentially expressed proteins were related to photosynthesis, glyoxylate metabolism, N metabolism, and anthocyanin biosynthesis. Finally, to verify the iTRAQ data, 12 representative genes encoding differentially expressed proteins were analyzed via quantitative real-time PCR, and these genes differed in transcriptional and translational expression levels. Our proteomic study contributes to understanding the metabolic pathways and biological processes involved in fruit color changes in different cultivars of A. arguta. These data and analyses will provide new insight into the development of kiwifruit flesh color.

Studies on anthocyanin biosynthesis have been mainly concentrated on the fruit, whereas few have focused the mechanism of flower coloration in kiwifruit. Here, we report that the structural gene, AeCHS, is involved in anthocyanin accumulation and indispensable for normal petal coloration in Actinidia eriantha. Petals from three different species including Actinidia eriantha (red petals), Actinidia hemsleyana (light pink petals) and Actinidia arguta (white petals) were selected for anthocyanin determination and gene expression analysis. The anthocyanin components in A. eriantha were significantly higher than in A. hemsleyana or A. arguta. Consistently, gene expression profiles suggested that AeCHS expression in A. eriantha was higher than in A. hemsleyana or A. arguta. Cluster analysis showed that AeCHS was clustered into a single group and distinctly separated from other genes, indicating the expression pattern of AeCHS gene was different from any other. Additionally, correlation analysis revealed AeCHS expression significantly correlated with anthocyanin content. The complete coding sequence of AeCHS was cloned from petals of A. eriantha ‘Zaoxu’, showing the length of AeCHS was 1170 bp encoding a protein of 389 amino acids. AeCHS was located in the cytoplasm, indicating it is indeed a structural gene involved in anthocyanin biosynthesis. AeCHS silencing performed by infiltration grafting-mediated virus-induced gene silencing (VIGS) reduced petal anthocyanin content and bleached red petals in A. eriantha. Our results confirm a crucial role of AeCHS in anthocyanin biosynthesis and accumulation in A. eriantha petals; furthermore, they offer important basic information and constitute a reference point for further research.

Recently, there has been a tremendous increase in the cultivated area of kiwifruit in China. However, the low tolerance of most cultivars to waterlogging largely halted its expansion in waterlogged areas. Previously, some genotypes from Actinidia valvata, like KR5, were proved to be highly tolerant for waterlogging stress. ERF transcription factors, belong to the AP2/ERF superfamily, have played key roles in adaptation to waterlogging stress in numerous plant species. In this study, a total of 131 AvERF genes were identified based on the full-length transcriptome analysis data from KR5. By clustering with Arabidopsis thaliana ERFs, 131 AvERF proteins were sorted into eleven clades and renamed as AvERF1 to AvERF131. Within the same group, similar motifs for AvERFs were found in all members by MEME online tool. According to FPKM analysis, the expression of AvERF-VIIs in KR5 under waterlogging conditions was strongly promoted compared to other group members. Six genes from AvERF-VIIs (AvERF73, AvERF75, AvERF77, AvERF78, AvERF79, and AvERF80) were chosen based on the higher fold changes in their expression against waterlogging. Moreover, their expression was evaluated in two tolerant genotypes: KR5 and KR1 from A. valvata, and two sensitive genotypes ‘Xuxiang’ and ‘Hayward’ from A. chinensis var. deliciosa during waterlogging stress by qRT-PCR. AvERF73 and AvERF78 were specifically induced in waterlogging-tolerant genotypes, but relatively low in the sensitive genotypes, indicating their positive roles in waterlogging tolerance. Both AvERF73 and AvERF78 had transcriptional activation activity. In the present study, we identified and characterized AvERFs into KR5 to reveal their importance in determining the waterlogging tolerance of kiwifruit.

The anthocyanin biosynthetic pathway regulated by exogenous and endogenous factors through sophisticated networks has been extensively studied in kiwifruit (Actinidia arguta). However, the role of micro RNAs (miRNAs) as regulatory factor in this process is largely unclear. Here, we demonstrate that miR858 is a negative regulator of anthocyanin biosynthesis by repressing the target gene AaMYBC1 in red-colored kiwifruit. Transient co-transformation in Nicotiana benthamiana confirmed that miR858 could target AaMYBC1, which was identified to be an R2R3-type tanscription factor (TF). Subcellular localization showed that AaMYBC1 was located in the nucleus, indicating AaMYBC1 protein could act as a transcriptional regulator in plant cells. Functional protein association network analysis and the yeast two hybrid (Y2H) assay revealed that AaMYBC1 and AabHLH42 interact with each other. Silencing of AaMYBC1 using the virus-induced gene silencing method in the core of A. arguta 'HB' ('Hongbaoshixing', a kind of red-fleshed A. arguta cultivar) fruits reduced the accumulation of anthocyanin and decreased the expression of late biosynthetic genes. miR858 overexpression played a stronger role than AaMYBC1 silencing in the inhibition of coloration. With overexpression of miR858, A. arguta did not present coloration, and anthocyanin was hardly detected. Together, these results clarify the negative regulatory role of miR858 in mediating anthocyanin biosynthesis and accumulation in A. arguta, providing novel insights into the molecular mechanism of anthocyanin biosynthesis.

Actinidia arguta is the most basal species in a phylogenetically and economically important genus in the family Actinidiaceae. To better understand the molecular basis of the Actinidia arguta chloroplast (cp), we sequenced the complete cp genome from A. arguta using Illumina and PacBio RS II sequencing technologies. The cp genome from A. arguta was 157,611 bp in length and composed of a pair of 24,232 bp inverted repeats (IRs) separated by a 20,463 bp small single copy region (SSC) and an 88,684 bp large single copy region (LSC). Overall, the cp genome contained 113 unique genes. The cp genomes from A. arguta and three other Actinidia species from GenBank were subjected to a comparative analysis. Indel mutation events and high frequencies of base substitution were identified, and the accD and ycf2 genes showed a high degree of variation within Actinidia. Forty-seven simple sequence repeats (SSRs) and 155 repetitive structures were identified, further demonstrating the rapid evolution in Actinidia. The cp genome analysis and the identification of variable loci provide vital information for understanding the evolution and function of the chloroplast and for characterizing Actinidia population genetics.

Cherry is an important diploid crop species belonging to the Rosaceae family, yet there are limited molecular tools available. For instance, stable reference genes have not yet been defined for use in quantitative real-time PCR across different experiments. Herein, 11 internal control genes were systematically evaluated for usefulness in gene expression normalization. The internal controls were tested across eight cherry genotypes, and tracked temporally, spatially and in response to abiotic stresses. The results indicated that no single reference gene was universally stable across various tissues and organs, in different developmental stages, or under different abiotic stresses in cherry. In eight tested cherry genotypes, candidate reference genes RPL13 and RPII were the most stable according to analysis by the geNorm program, and ACT was the most stable gene by NormFinder. In vegetative tissues and organs, the best normalization was achieved with a combination of CYP2, a-TUB, SAND-2, and RPL13, as determined by geNorm software, or RPL13, as determined by NormFinder. TEF2, CYP2, and ACT were identified as suitable reference genes for fruit and flower development, based on both geNorm and NormFinder analyses. To illustrate the suitability of these reference genes, expression of CHS and MYB10 genes was analyzed in various flower tissues and organs using the most stable and unstable reference genes for normalization. Our results indicated that the selected reference genes were suitable and reliable for cherry gene expression using qRT-PCR.

Kiwifruits are rich in nutrients beneficial to humans. Because forchlorfenuron (CPPU)-treatment after full bloom can enlarge fruit size, and significantly increase the income of farmers, it has been extensively used. However, CPPU might also influence fruit sugar and acid content, and storage performance. This study analyzed the differences in volatile emissions between CPPU-treated and water-treated kiwifruits after two, four, six, or eight days of storage, and differential gene expression related to these compounds using high-throughput sequencing. The number of volatile compounds was relatively high at the first two days of storage for both treated and control fruits, decreased in the following days, and increased again, although less significantly in CPPU-treated than in control fruits. Aldehydes in the control and treated groups showed a trend of stability vs. down-regulation, alcohols or terpenes showed high-low-high vs. down-regulation, and esters showed up-regulation vs. high-low-high, respectively. Only 60.12-66.68% of the genes obtained were mapped and 3370 new genes were annotated. Genes related to terpene biosynthesis were enriched, and, in CPPU-treated fruits, several genes related to hormone signal transduction were found in aldehydes, alcohols, and terpenes biosynthetic pathways. Although CPPU might influence the expression of genes encoding the core complex proteins in photosynthesis, its relationship with terpene synthesis is still unclear. Our results provided resources for the genetic annotation of kiwifruits, and revealed the impact of CPPU on the metabolism of their volatile compounds, laying the theoretical foundation for investigating the use of molecular techniques to inhibit the CPPU-related reduction of fruit quality.

The volatile compounds of 85 regional apricot cultivars native to China were characterized by headspace-solid phase microextraction coupled with gas chromatography–mass spectrometry. A total of 156 volatile compounds were tentatively detected, 62 of which were identified in apricots for the first time. The composition and concentration of the volatile compounds varied greatly among the cultivars, with the number of individual compounds per cultivar ranging from 39 to 85, at concentrations of 9.0 to 296.5 mg/kg fresh weight. The apricots from northwest China had the highest concentrations of volatile compounds, while those from the southwest had the lowest concentrations. Based on principal component analysis, the cultivars were divided into four groups characterized by their volatile profiles: 1) terpenoids; 2) aldehydes; 3) terpenoids and aldehydes; and 4) an absence of characteristic volatiles. The greatest diversity of volatile compounds was found in cultivars from northwest China, while the diversity ...

Studies on anthocyanin biosynthesis have been mainly concentrated on the fruit, whereas few have focused the mechanism of flower coloration in kiwifruit. Here, we report that the structural gene, AeCHS, is involved in anthocyanin accumulation and indispensable for normal petal coloration in Actinidia eriantha. Petals from three different species including Actinidia eriantha (red petals), Actinidia hemsleyana (light pink petals) and Actinidia arguta (white petals) were selected for anthocyanin determination and gene expression analysis. The anthocyanin components in A. eriantha were significantly higher than in A. hemsleyana or A. arguta. Consistently, gene expression profiles suggested that AeCHS expression in A. eriantha was higher than in A. hemsleyana or A. arguta. Cluster analysis showed that AeCHS was clustered into a single group and distinctly separated from other genes, indicating the expression pattern of AeCHS gene was different from any other. Additionally, correlation analysis revealed AeCHS expression significantly correlated with anthocyanin content. The complete coding sequence of AeCHS was cloned from petals of A. eriantha &lsquo, Zaoxu&rsquo, showing the length of AeCHS was 1170 bp encoding a protein of 389 amino acids. AeCHS was located in the cytoplasm, indicating it is indeed a structural gene involved in anthocyanin biosynthesis. AeCHS silencing performed by infiltration grafting-mediated virus-induced gene silencing (VIGS) reduced petal anthocyanin content and bleached red petals in A. eriantha. Our results confirm a crucial role of AeCHS in anthocyanin biosynthesis and accumulation in A. eriantha petals, furthermore, they offer important basic information and constitute a reference point for further research.

As important regulators, miRNAs could play pivotal roles in regulation of fruit coloring. Actinidia arguta is a newly emerged fruit tree with extensively application prospects. However, miRNAs involved in A. arguta fruit coloring are unknown. In this study, A. arguta fruit were investigated at three developmental stages by small RNAs high-throughput sequencing. A total of 482 conserved miRNAs corresponding to 526 pre-miRNAs and 581 novel miRNAs corresponding to 619 pre-miRNAs were grouped into 46 miRNA families. Target gene prediction and analysis revealed that miR858, a strongly candidate miRNA, was involved in anthocyanin biosynthesis in which contributes to fruit coloring. The anthocyanin level was determined in three A. arguta cultivars by UPLC-MS/MS (ultra-performance liquid chromatography coupled with tandem mass spectrometry). In addition, qPCR (quantitative real-time PCR), cluster analysis were conducted as well as correlation analysis. All results were combined to propose a model in which describes an association of miRNA and anthocyanin biosynthesis in A. arguta. The data presented herein is the first report on miRNA profile analysis in A. arguta, which can provide valuable information for further research into the regulation of the miRNAs in anthocyanin biosynthesis and fruit coloring.

Kiwifruit bacterial canker is a devastating disease threatening kiwifruit production. To clarify the defense mechanism in response to Pseudomonas syringae pv. actinidiae (Psa), we observed phenotypic changes in resistant Huate (HT) and susceptible Hongyang (HY) kiwifruit varieties at 0, 12, 24, 48, 96, and 144 hour after inoculation (hai) with Psa. Brown lesions appeared in the inoculation areas 12 hai in HY shoots, and the lesion length gradually increased from 24 to 144 h. In contrast, no lesions were found in HT shoots at any time points. Furthermore, RNA-seq analysis showed significantly more differentially expressed genes between HT and HY at 12 hai than at any other time point. According to weighted gene co-expression network analysis, five modules were notably differentially expressed between HT and HY; pathway mapping using the Kyoto Encyclopedia of Gene and Genomes database was performed for the five modules. In MEgreenyellow and MEyellow modules, pathways related to"plant-pathogen interaction", "Endocytosis", "Glycine, serine and threonine metabolism", and "Carbon fixation in photosynthetic organisms" were enriched, whereas in the MEblack module, pathways related to "protein processing in endoplasmic reticulum", "plant-pathogen interaction", and "Glycolysis / Gluconeogenesis" were enriched. In particular, the Pti1 and RPS2 encoding effector receptors, and the NPR1, TGA, and PR1 genes involved in the salicylic acid signaling pathway were significantly up-regulated in HT compared with HY. This indicates that the effector-triggered immunity response was stronger and that the salicylic acid signaling pathway played a pivotal role in the Psa defense response of HT. In addition, we identified other important genes, involved in phenylpropanoid biosynthesis and Ca2+ internal flow, which were highly expressed in HT. Taken together, these results provide important information to elucidate the defense mechanisms of kiwifruit during Psa infection.

Lotus (nelumbo) is a traditional Chinese medical herb, and alkaloids are responsible for its pharmaceutical activities. Therefore, a rapid, validated method to determine alkaloids in lotus leaves is useful for its quality control. The goal of this work was to develop and validate an analytical method for the identification and quantitation of the bioactive alkaloids of extracts from lotus leaf and classification of lotus germplasm based on alkaloid concentrations. Solid-phase extraction was used prior to high-performance liquid chromatography coupled with photodiode array detection at 272 nm and tandem electrospray ionization triple quadrupole mass spectrometry for analysis. Nuciferine and O-nornuciferine were the dominant compounds in lotus used for seed production and some used for flower production. However, anonaine, roemerine, and N-nornuciferine were abundant only in some lotus flowers. All the lotuses were classified into four groups by principal component analysis of alkaloid content: 10 flower an...

The composition and concentrations of flavonoids in the leaves of 107 different cultivars or taxa of lotus ( Nelumbo ) were characterized and compared, and the effect of drying or fresh-freezing leaves on flavonoid composition and content was investigated. Results show that significantly higher flavonoid levels were present in fresh-frozen than in dried tissue, while preparation technique produced no effects on flavonoid composition. Quercetin derivatives including hyperoside, isoquercitrin, and quercetin 3- O -glucuronide were the dominant flavonoids in lotus leaves, accounting on average for 15.87%, 16.26%, and 50.20% of total flavonoids, respectively. Lotus taxa used in seed production had the highest flavonoid content (20–45% higher than other cultivars). Principal component analysis allowed the cultivars to be divided into three well-characterized groups based on their flavonoid content. The results of this study should be of value to the lotus-processing industry with regard to tea and food additive production.

Flavonoid composition and concentration were investigated in 12 different tissues of 'Ti-1' lotus (Nelumbo nucifera) by high performance liquid chromatography equipped with photodiode array detection tandem electrospray ionization mass spectrometry (HPLC-DAD-ESI-MS(n)). A total of 20 flavonoids belonging to six groups (myricetin, quercetin, kaempferol, isohamnetin, diosmetin derivatives) were separated and identified. Myricetin 3-O-galactoside, myricetin 3-O-glucuronide, isorhamnetin 3-O-glucuronide and free aglycone diometin (3',5,7-trihydroxy-4'-methoxyflavone) were first reported in lotus. Flavonoid composition varied largely with tissue type, and diverse compounds (5-15) were found in leaf and flower stalks, flower pistils, seed coats and embryos. Flower tissues including flower petals, stamens, pistils, and, especially, reproductive tissue fruit coats had more flavonoid compounds (15-17) than leaves (12), while no flavonoids were detectable in seed kernels. The flavonoid content of seed embryos was high, 730.95 mg 100g(-1) DW (dry weight). As regards the other tissues, mature leaf pulp (771.79 mg 100 g(-1) FW (fresh weight)) and young leaves (650.67 mg 100 g(-1) FW) had higher total flavonoid amount than flower stamens (359.45 mg 100 g(-1) FW) and flower petals (342.97 mg 100g(-1) FW), while leaf stalks, flower stalks and seed coats had much less total flavonoid (less than 40 mg 100 g(-1) FW).