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Litchi and longan are tropic/subtropic fruits harboring recalcitrant seeds that are covered with sugar-rich arils as the edible part. A rapid sugar content decline, called sugar receding, in the arils after the fruit maturation largely reduces the fruit quality, however, the mechanism is unclear. Litchi and longan fruits grow and mature in a hot and rainy season with dry spells between rainfalls. Here, we found that the seed maturation was around 2 weeks earlier than the fruit maturation, after which the sugar contents of the arils significantly decreased, while the fruits could stay on the tree for 1–2 months with high seed vigor. A continuously low-level fruit drop after the seed maturation resulted in continuous seed germination and seedling establishment in around 2–3 months. Blocking assimilate supply by storage of detached fruits or on-tree girdling-plus-defoliation for 7 days, the aril sugar contents of the treated fruits significantly decreased, while the sugar levels and vigor of the seeds increased, implying that the arils are sugar sources to maintain or even enhance the seed vigor and suggesting that sugar receding in arils benefits the recalcitrant seeds of litchi and longan to cope with dry spells after maturation. [ABSTRACT FROM AUTHOR]

Pericarp browning is the key factor for the extension of shelf life and the maintenance of the commercial value of harvested litchi fruit. Water loss is considered a leading factor of pericarp browning in litchi fruit. In this study, based on the distinct structure of litchi fruit, which is a special type of dry fruit with the aril as the edible part, the effects of water supply via pedicel (WSP) treatment on pericarp browning and the fruit quality of litchi were investigated. Compared with the packaging of the control fruit at 25 °C or 4 °C, the WSP treatment was found to significantly reduce pericarp browning and the decay of litchi fruit. The WSP-treated fruit had a higher L* value, total anthocyanin content, and pericarp water content, and the pericarp was thicker. The WSP treatment significantly suppressed the increase in the electrolyte leakage of the pericarp and maintained higher ascorbic acid (AA) contents in the aril. In addition, the WSP treatment was effective in reducing the activity and gene expression of browning-related genes Laccase (ADE/LAC) and Peroxidase (POD) during the storage period. In conclusion, the WSP treatment could be an effective method to delay pericarp browning and maintain the quality of harvested litchi fruit, and this further supports that litchi fruit has dry fruit characteristics. [ABSTRACT FROM AUTHOR]

As zinc finger protein transcription factors (TFs), the molecular mechanism of Cys-Cys-Cys-His (CCCH) TFs in regulating plant development, growth and stress response has been well studied. However, the roles of CCCH TFs in fruit ripening are still obscure. Herein, we report that MaCCCH33-like2 TF and its associated proteins modulate the fruit softening of 'Fenjiao' bananas. MaCCCH33-like2 interacts directly with the promoters of three genes: isoamylase2 (MaISA2), sugar transporter14-like (MaSUR14-like) and β- d -xylosidase23 (MaXYL23), all of which are responsible for encoding proteins involved in the degradation of starch and cell wall components. Additionally, MaCCCH33-like2 forms interactions with abscisic acid–insensitive 5 (ABI5)-like and ethylene F-box protein 1 (MaEBF1), resulting in enhanced binding and activation of promoters of genes related to starch and cell wall degradation. When MaCCCH33-like2 is transiently and ectopically overexpressed in 'Fenjiao' banana and tomato fruit, it facilitates softening and ripening processes by promoting the degradation of cell wall components and starch and the production of ethylene. Conversely, the temporary silencing of MaCCCH33-like2 using virus-induced gene silencing (VIGS) inhibits softening and ripening in the 'Fenjiao' banana by suppressing ethylene synthesis, as well as starch and cell wall degradation. Furthermore, the promoter activity of MaCCCH33-like2 is regulated by MaABI5-like. Taken together, we have uncovered a novel MaCCCH33-like2/MaEBF1/MaABI5-like module that participates in fruit softening regulation in bananas. [ABSTRACT FROM AUTHOR]

The projected rise in global ambient temperature by 3–5 °C by the end of this century, along with unpredicted heat waves during critical crop growth stages, can drastically reduce grain yield and will pose a great food security challenge. It is therefore important to identify wheat genetic resources able to withstand high temperatures, discover genes underpinning resilience to higher temperatures, and deploy such genetic resources in wheat breeding to develop heat-tolerant cultivars. In this study, 180 accessions of synthetic hexaploid wheats (SHWs) were evaluated under normal and late wheat growing seasons (to expose them to higher temperatures) at three locations (Islamabad, Bahawalpur, and Tando Jam), and data were collected on 11 morphological and yield-related traits. The diversity panel was genotyped with a 50 K SNP array to conduct genome-wide association studies (GWASs) for heat tolerance in SHW. A known heat-tolerance locus, TaHST1, was profiled to identify different haplotypes of this locus in SHWs and their association with grain yield and related traits in SHWs. There was a 36% decrease in grain yield (GY), a 23% decrease in thousand-grain weight (TKW), and an 18% decrease in grains per spike (GpS) across three locations in the population due to the heat stress conditions. GWASs identified 143 quantitative trait nucleotides (QTNs) distributed over all 21 chromosomes in the SHWs. Out of these, 52 QTNs were associated with morphological and yield-related traits under heat stress, while 15 of them were pleiotropically associated with multiple traits. The heat shock protein (HSP) framework of the wheat genome was then aligned with the QTNs identified in this study. Seventeen QTNs were in proximity to HSPs on chr2B, chr3D, chr5A, chr5B, chr6D, and chr7D. It is likely that QTNs on the D genome and those in proximity to HSPs may carry novel alleles for heat-tolerance genes. The analysis of TaHST1 indicated that 15 haplotypes were present in the SHWs for this locus, while hap1 showed the highest frequency of 25% (33 SHWs). These haplotypes were significantly associated with yield-related traits in the SHWs. New alleles associated with yield-related traits in SHWs could be an excellent reservoir for breeding deployment. [ABSTRACT FROM AUTHOR]

The fruit of Litchi chinensis contains high levels of proanthocyanidins (PAs) in the pericarp. These substances can serve as substrates of laccase-mediated rapid pericarp browning after the fruit is harvested. In this study, we found that the major PAs in litchi pericarp were (−)-epicatechin (EC) and several procyanidins (PCs), primarily PC A2, B2, and B1, and the EC and the PC content decreased with the development of the fruit. RNA-seq analysis showed that 43 early and late structure genes related to flavonoid/PA biosynthesis were expressed in the pericarp, including five ANTHOCYANIDIN REDUCTASE (ANR), two LEUCOANTHOCYANIDIN REDUCTASE (LAR), and two ANTHOCYANIDIN SYNTHASE (ANS) genes functioning in the PA biosynthesis branch of the flavonoid pathway. Among these nine PA biosynthesis-related genes, ANR1a, LAR1/2, and ANS1 were highly positively correlated with changes in the EC/PC content, suggesting that they are the key PA biosynthesis-related genes. Several transcription factor (TF) genes, including MYB, bHLH, WRKY, and AP2 family members, were found to be highly correlated with ANR1a, LAR1/2, and ANS1, and their relevant binding elements were detected in the promoters of these target genes, strongly suggesting that these TF genes may play regulatory roles in PA biosynthesis. In summary, this study identified the candidate key structure and regulatory genes in PA biosynthesis in litchi pericarp, which will assist in understanding the accumulation of high levels of browning-related PA substances in the pericarp. [ABSTRACT FROM AUTHOR]

Recent studies have confirmed that chlorophyllase (CLH), a long-found chlorophyll (Chl) dephytylation enzyme for initiating Chl catabolism, has no function in leaf senescence-related Chl breakdown. Yet, CLH is considered to be involved in fruit degreening and responds to external and hormonal stimuli. The purpose of this work was to elucidate in detail the biochemical, structural properties, and gene expression of four CLHs from the Solanum lycopersicum genome so as to understand the roles of Solanum lycopersicum chlorophyllases (SlCLHs). SlCLH1/4 were the predominantly expressed CLH genes during leaf and fruit development/ripening stages, and SlCLH1 in mature green fruit was modulated by light. SlCLH1/2/3/4 contained a highly conserved GHSXG lipase motif and a Ser-Asp-His catalytic triad. We identified Ser159, Asp226, and His258 as the essential catalytic triad by site-directed mutagenesis in recombinant SlCLH1. Kinetic analysis of the recombinant enzymes revealed that SlCLH1 had high hydrolysis activities against Chl a, Chl b, and pheophytin a (Phein a), but preferred Chl a and Chl b over Phein a; SlCLH2/3 only showed very low activity to Chl a and Chl b, while SlCLH4 showed no Chl dephytylation activity. The recombinant SlCLH1/2/3 had different pH stability and temperature optimum. Removal of the predicted N-terminal processing peptide caused a partial loss of activity in recombinant SlCLH1/2 but did not compromise SlCLH3 activity. These different characteristics among SlCLHs imply that they may have different physiological functions in tomato. [ABSTRACT FROM AUTHOR]

The distinct dark-red skin of Huaniu apples renders them attractive to customers. However, the mechanism that leads to the development of the color of the fruit is unclear. In this study, we found that compared with red Fuji (a bright-red apple cultivar), Huaniu apples had higher contents of (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-gallocatechin gallate (GCG), and procyanidins (PCs) B2 and C1 in the peel, which implies that the polymerization of the flavanols and PCs may be correlated with the dark-red skin of the fruit. Using EC as a substrate, we purified an enzyme from Huaniu peel. We performed protein sequencing and discovered that the enzyme was a polyphenol oxidase (PPO). The molecular weight of the enzyme was approximately 140 kDa, which we estimated by native-PAGE and SDS-PAGE, while it was 61 kDa by urea-SDS-PAGE, from which we discovered that the PPO was a dimer. We observed the lowest Km value for catechol (0.60 mM), and the best substrate was 4-methylcatechol, with a Vmax of 526.32 U mg−1 protein. EC is a suitable natural substrate, with a Km value of 1.17 mM, and 55.27% of the Vmax/Km of 4-methylcatechol. When we used EC as a substrate, the optimum temperature and pH of the PPO were 25 °C and 5.0, respectively. In summary, we purified a dimeric PPO from Huaniu apples that showed high activity to EC, which might catalyze the polymerization of flavanols and PCs and lead to the dark-red color development of the fruit. [ABSTRACT FROM AUTHOR]

SUMMARY: Ethylene signaling appears critical for grape bud dormancy release. We therefore focused on identification and characterization of potential downstream targets and events, assuming that they participate in the regulation of dormancy release. Because ethylene responding factors (ERF) are natural candidates for targets of ethylene signaling, we initially characterized the behavior of two VvERF‐VIIs, which we identified within a gene set induced by dormancy release stimuli. As expected, these VvERF‐VIIs are localized within the nucleus, and are stabilized upon decreases in oxygen availability within the dormant buds. Less expected, the proteins are also stabilized upon hydrogen cyanamide (HC) application under normoxic conditions, and their levels peak at deepest dormancy under vineyard conditions. We proceeded to catalog the response of all bud‐expressed ERFs, and identified additional ERFs that respond similarly to ethylene, HC, azide and hypoxia. We also identified a core set of genes that are similarly affected by treatment with ethylene and with various dormancy release stimuli. Interestingly, the functional annotations of this core set center around response to energy crisis and renewal of energy resources via autophagy‐mediated catabolism. Because ERF‐VIIs are stabilized under energy shortage and reshape cell metabolism to allow energy regeneration, we propose that: (i) the availability of VvERF‐VIIs is a consequence of an energy crisis within the bud; (ii) VvERF‐VIIs function as part of an energy‐regenerating mechanism, which activates anaerobic metabolism and autophagy‐mediated macromolecule catabolism; and (iii) activation of catabolism serves as the mandatory switch and the driving force for activation of the growth‐inhibited meristem during bud‐break. Significance Statement: The ability of various stresses, which are rationally expected to inhibit growth, to paradoxically activate growth of the dormant bud meristem, has been an enigma for decades. Collectively, our data propose: (i) that stress mediates energy regeneration under conditions of energy crisis, by induction of ethylene‐activated anaerobic metabolism and macromolecule catabolism; (ii) that activation of autophagy‐mediated catabolism serves as the mandatory switch and the driving force for activation of the growth‐inhibited meristem during bud‐break. [ABSTRACT FROM AUTHOR]

The aim of this research was to obtain the optimum gas compositions of controlled atmosphere (CA) for Chinese flowering cabbage stored at 10°C and to clarify the molecular mechanism of senescence during storage under two selected CA conditions. Two CA experiments were conducted. The first one was on low O2 (5% and 10%) and high CO2 (5% and 10%) combinations, and the second one was on air O2 (20.4%) and high CO2 (5%, 10%, 15%, 30%, and 45%) combinations. It was shown that CA2 (5% O2 + 10% CO2) achieved the best beneficial effects on cabbage quality among all the treatments. CA2 and CA7 (20.4% O2 + 15% CO2), significantly decreased the activities of Chlase and MDCase, and down‐regulated the transcript abundances of the BrChlase, BrPAO, BrRCCR, and BrSAG12. Practical applications: Rapid leaf yellowing and deterioration are the key problems limiting the shelf life and marketing of Chinese flowering cabbage. While CA2 treatment was highly effective in preventing stalks from losing turgor, delaying leaf yellowing, and maintained 78.3% of chlorophyll, 81.6% of ascorbic acid, 68.1% of soluble protein, and 85.4% of soluble sugar after 8 days of storage. The CA2 storage showed the best effect in blocking the transcription of BrRCCR, whereas CA7 showed the best effect in repressing the transcription of BrSAG12. These findings present favorable CA compositions for the postharvest storage and transportation of Chinese flowering cabbage and provide insight into the molecular mechanisms of senescence in this vegetable. [ABSTRACT FROM AUTHOR]

Abstract: An anthocyanin degradation‐related laccase (LcADE/LAC) from lychee fruit was found to be responsible for the pericarp browning. In this study, LcADE/LAC was purified and characterized for better control of laccase‐based browning. The optimum pH for LcADE/LAC activities was 5.0–6.0, with less than 20% of the activity retained at pH 3.0. The optimum temperature is 45 °C, and the activity is thermostable at this temperature. The enzyme was inhibited by 1 mM Fe2+, but induced by 0.1 mM Fe3+. Na2SO3 and l‐cysteine highly inhibited the activity at 0.1 mM, while kojic and phytic acids inhibited 40 and 43%, respectively, at 1 mM. Na2SO3 inhibited the activity in a noncompetitive model with a Ki value of 33.1 μM, and the inhibition increased when pH decreased to 3.5. In postharvest fruit, the enzyme activity and LcADE/LAC gene expression were strongly inhibited by SO2‐HCl treatment. Practical applications: The present study systematically characterizes a pericarp browning related laccase (LcADE/LAC) from lychee. The high sensitivity of the enzyme to low pH and several inhibitors, such as SO2, l‐cysteine, and kojic acid and phytic acids, will help in the development of more efficient strategies for browning control of lychee pericarp or other laccase‐based food browning. [ABSTRACT FROM AUTHOR]

Litchi (Litchi chinensis Sonn.) fruit is known for its rich source of phenolics. Litchi pericarp contains high levels of epicatechin that may form oligomers of various lengths. Except for several A or B type epicatechin dimers, other soluble oligomers have rarely been identified in the pericarp. Here, bioassay-guided column fractionation was applied to isolate bioactive phenolics from aqueous pericarp extract. A fraction (S3) was obtained by two rounds of Sephadex LH-20 column chromatography, and showed higher antioxidant activity and inhibition on the proliferation of human lung cancer cells (A549) than Litchi anthocyanins. S3 was further separated to isolate fractions P1-P4, which all showed higher antioxidant activity than vitamin C. P3 showed 32.9% inhibition on A549 cells at 30 μg/mL, higher than other fractions and cis-Dichlorodiamineplatinum (DDP, 0.5 μg/mL), but not as high as the combination of the four fractions. Using HPLC-Q-TOF-MS/MS, one B-type and complex A/B type epicatechin trimers were identified in P3; another B-type and two A/B-type trimers were identified in P4. P1 and P2, containing epicatechin and proanthocyanidin B2, respectively, showed no cell inhibition at 30 μg/mL. It is the first time that the two B type trimers of epicatechins (Litchitannin B1 and B2), have been found in Litchi species. The identified proanthocyanidins were detected in the pericarp of the young fruit, and the levels of the compounds decreased as the fruit developed, correlating to the decreasing patterns of the expression of LcLAR and LcANR, two key genes in the catechin biosynthesis pathway. [ABSTRACT FROM AUTHOR]

Calcium-dependent protein kinase (CDPK) is an important Ca2+sensor in plant development and responses to stress stimuli. Banana fruit is a typical climacteric- and chilling-sensitive fruit. The roles ofCDPKgenes in the ripening and chilling response of banana fruit are unclear. We isolated a cDNA fragment with full-length codingMaCDPK7(HM061075) from fruit peel tissue. Induction ofMaCDPK7expression in fruit peel was observed 0.5 h after phytohormone ethylene treatment, earlier than the up-regulation ofMaACO1andMaACS1, coding a 1-aminocyclopropane-1-carboxylate oxidase and 1-aminocyclopropane-1-carboxylate synthase, respectively. Penetration of calcium signaling blockers, EGTA, or LaCl3inhibited the ripening and gene expression ofMaCDPK7,MaACO1, andMaACS1in thein vitrocultured peel pieces, but Ca2+application removed the inhibitory effect of EGTA and LaCl3. This suggested thatMaCDPK7might be a positive regulator involved in the calcium signaling in banana fruit ripening. Under temperature stresses, we found thatMaCDPK7gene expression increased 3 h after hot water dipping (HWD). The HWD-treated fruits exhibited markedly less chilling injury (CI) than control fruits in cold storage. Stored at 7°C (CI temperature) dramatically increasedMaCDPK7gene expression, while pre-treatment of HWD repressed the induction in cold storage. These results show that theMaCDPK7gene is involved in regulating banana fruit ripening and chilling resistance induced by heat treatment. [ABSTRACT FROM AUTHOR]

BACKGROUND: To understand the mechanisms leading to the enhanced chilling resistance of banana by hot-water dipping (HWD, 52 °C for 3 min), we investigated the effect of a 0.5-24 h delay between HWD and cold storage on chilling resistance and the change related to the metabolism of reactive oxygen species (ROS). RESULTS: The HWD-treated fruit with a delay of less than 6 h exhibited markedly less chilling injury than the non-heated control fruit, while a delay more than 6 h resulted in significant loss in chilling resistance. Increased hydrogen peroxide content and rate of superoxide radical production were detected in the fruit at 0.5-1.5 h after HWD treatment, and the levels declined with a longer delay, which may be correlated with the enhanced gene expression levels of the gene coding for a ROS-generating related enzyme, NADPH oxidase ( MaNOX). Enhanced activities and gene expression of an ascorbate peroxidase ( MaAPX) were recorded in the fruit at 1.5-6 h after the treatment, and after 6 h the ascorbate peroxidase levels decayed to the levels as the control fruit. The higher APX gene expression was maintained in the treated fruit with a 3 h delay during the subsequent cold storage at 7 °C, correlating with the enhanced chilling resistance. CONCLUSION: The HWD-treated fruit left at ambient temperature up to 6 h prior to cold storage maintained the effect of heat treatment and transiently increased ROS content, and the ascorbate peroxidase activity that occurred 0.5-6 h after the treatment may be correlated with the elevated chilling resistance induced by HWD treatment. Copyright © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: The application of genomic approaches may serve as an initial step in broadening our understanding of the complex network of biochemical and cellular processes responsible for the regulation and execution of grape-bud dormancy release. However, bud tissue in general, and the dormant bud in particular, are under-represented in the public Vitis genomic resources. Here we describe a large-scale grape-bud EST collection representing a wide range of bud developmental stages. A collection of 5516 consensus sequences is presented, of which 59% were not included within the Vitis TIGR collection at the time of current analysis. About 22% of these transcripts bear no resemblance to any known plant transcript and thus corroborate the need for this targeted EST collection. The added value of the presented EST collection lies in the conferred ability to compare EST frequencies between the different cDNA libraries. Such comparison was implemented and allowed us to identify several genes/functions whose expression is altered in response to the dormancy-release treatment. Based on this analysis, it is suggested that oxidative stress, calcium signaling, intracellular vesicle trafficking and anaerobic mode of carbohydrate metabolism play a role in the regulation and execution of grape-bud dormancy release. [Copyright &y& Elsevier]

Postharvest browning of litchi fruit pericarp is a major problem, resulting in accelerated shelf life and reduced commercial value of the fruit. The browning was generally thought to be a rapid degradation of red pigments caused by polyphenol oxidase (PPO) and peroxidase (POD). This work is conducted to understand the role of POD in anthocyanin degradation in litchi pericarp, which is less understood than PPO. POD activity in the pericarp increased consistently with skin browning index during storage of litchi fruit, but was negatively associated with anthocyanin concentration. Although POD cannot directly oxidize litchi anthocyanin in the presence of H2O2 in vitro, the anthocyanin content decreased rapidly after the addition of guaiacol solution, which indicated that the anthocyanin degradation by POD exhibited a coupled oxidation mechanism. Furthermore, anthocyanidin, produced by hydrolysis of the purified anthocyanin, could act as a substrate of POD. Thus, enzymatic browning of litchi fruit pericarp caused by POD may involve an anthocyanase–anthocyanin–phenolic–H2O2 reaction. [Copyright &y& Elsevier]

Brunfelsia calycina flowers lose anthocyanins rapidly and are therefore well suited for the study of anthocyanin degradation mechanisms, which are unclear in planta. Here, we isolated an anthocyanin-β-glycosidase from B. calycina petals. The MS/MS (Mass Spectrometry) peptide sequencing showed that the enzyme (72 kDa) was a β-xylosidase (BcXyl). The enzyme showed high activity to p-Nitrophenyl-β-d-galactopyranoside (pNPGa) and p-Nitrophenyl-β-d-xylopyranoside (pNPX), while no activity to p-Nitrophenyl-β-d-glucopyranoside (pNPG) or p-Nitrophenyl-β-D-mannopyranoside (pNPM) was seen. The optimum temperature of BcXyl was 40 °C and the optimum pH was 5.0. The enzyme was strongly inhibited by 1 mM D-gluconate and Ag+. HPLC (High Performance Liquid Chromatography) analysis showed that BcXyl catalyzed the degradation of an anthocyanin component of B. calycina, and the release of xylose and galactose due to hydrolysis of glycosidic bonds by BcXyl was detected by GC (Gas Chromatography) /MS. A full-length mRNA sequence (2358 bp) of BcXyl (NCBI No. MK411219) was obtained and the deduced protein sequence shared conserved domains with two anthocyanin-β-glycosidases (Bgln and BadGluc, characterized in fungi). BcXyl, Bgln and BadGluc belong to AB subfamily of Glycoside hydrolase family 3. Similar to BcPrx01, an anthocyanin-degradation-related Peroxidase (POD), BcXyl was dramatically activated at the stage at which the rapid anthocyanin degradation occurred. Taken together, we suggest that BcXyl may be the first anthocyanin-β-glycosidase identified in higher plants. [ABSTRACT FROM AUTHOR]

‘Ambrosia’ apple is one of the emerging apple cultivars that have been gaining popularity in North America due to its superior eating quality. An effective postharvest storage regime has been established for optimal storage and quality maintenance. Unfortunately, a postharvest physiological disorder has often been reported, which shows symptoms similar to low temperature induced soft scald in ‘Honeycrisp’. Therefore, a delayed cooling strategy prior to storage has been developed and implemented as a successful and economical method to prevent this disorder. In order to reveal the molecular mechanism of soft scald development and delayed cooling in combating this low temperature induced disorder, a quantitative proteomic investigation employing stable isotope dimethylation labeling by peptides was conducted on ‘Ambrosia’ apples from three commercial orchards in BC, Canada. Quantitative changes in protein abundance in association with disorder development and in response to delayed cooling treatment after one and three month storage were found. Among the quantified proteins, 495 and 575 proteins were commonly presented in three biological replicates after one and three month storage; respectively. Among them, the abundance of 78 and 88 proteins were found to be significantly changed in response to delayed cooling as compared with normal cold storage for one and three months, respectively. These identified proteins were functionally annotated using MAPMAN software, which identified glycolysis, lipid metabolism, amino acids (including GABA shunt), hormone response, stress and signaling, redox and glutathione metabolism as the major pathways influenced by the delayed cooling treatment. A principal component analysis (PCA) revealed groups of proteins that play a major role in response to disorder development and a negative response to delayed cooling. In addition, an ABC transporter protein F family is correlated to the delayed cooling treatment. This study demonstrates the potential mechanism of the biological effect of delayed cooling on apple fruit at the proteomic level. It also provides in-depth insight on molecular mechanisms of the delayed cooling treatment in apples. [ABSTRACT FROM AUTHOR]

Bananas ( Musa , AAA group) develop a bright yellow appearance when ripen at temperatures between 18 °C and 24 °C. At high ambient temperatures, the fruit display green-ripe and become un-acceptable in the market. To understand the mechanisms that govern the color changing during banana green-ripening, the influence of high temperature on chlorophyll degradation at various ripening stages were investigated. After ripening initiation, the fruit were subjected to 8 different temperature changing regimes at both 20 °C and 30 °C in 5 days. The ripening and senescence parameters were monitored and relevant gene expression was analyzed by RNA gel blot hybridization. Temperature during the first 3 days, or precisely the stage around the on-set of the respiration peak, was found to be critical for color formation in bananas. When the fruit were held at 30 °C at this stage, the fruit developed green-ripe with >30% of the original chlorophyll remaining, regardless the other stages were at 20 °C. The repressed chlorophyll degradation by 30 °C was positively correlated to the reduced expression of several key genes functioning in chlorophyll degradation, MaSGR , MaNYC and MaPaO , which behaved in a closely temperature responding manner. Conversely to chlorophyll degradation patterns, moving to 30 °C induced fruit respiration rate, the expression of MaACO , an ethylene synthesis related gene, and accelerated the decrease in fruit firmness and chlorophyll florescence ( F v / F m ), indicating that the ripening of the fruit was accelerated at 30 °C. Accordingly, in the context of fruit ripening but under not agreeable temperature (30 °C), the expression of chlorophyll degradation genes in bananas was predominantly regulated by temperature, not responding to the fruit ripening proceeding. Interestingly, by using the alternating temperature system, we here the first time reported the sensitivity of chlorophyll degradation genes, MaSGR , MaPAO and MaNYC , to high temperature during banana fruit ripening. [ABSTRACT FROM AUTHOR]

• The MaC2H2-like is closely related to fruit ripening disorder by chilling stress. • MaC2H2-like activates the transcription level of fruit softening-related genes. • MaEBF1 interacting MaC2H2-like enhanced the expression of softening-related genes. • MaC2H2-like- overexpressing promotes fruit ripening in 'Fenjiao' banana. As one of the largest transcription factor families, C2H2 zinc finger proteins contain a zinc finger motif and a conserved DNA-binding homeodomain. Although C2H2 zinc finger proteins have been found to play an essential role in ethylene biosynthetic and cold stress in banana fruit, their transcriptional regulatory mechanisms involved in the softening of 'Fenjiao' banana remain largely elusive. In this study, a new MaC2H2-like gene was identified, which is closely related to fruit softening. MaC2H2-like localizes in the nucleus. MaC2H2-like activated the transcription of four starch (MaBAM4 , MaBAM6 , MaISA2 and MaPWD1) and five cell wall (MaEXP-A2 , MaEXP-A8 , MaSUR14 , MaSUR14-like and MaXYL32) degradation-related genes, by specifically interacting with their promoters. Protein-protein interaction assays showed that MaC2H2-like cooperates with ethylene-insensitive 3-binding F-box protein (MaEBF1) in vitro and vivo , and their interaction enhanced the binding and activated the promoter activities of MaBAM4 , MaPWD1 , MaISA2 , MaEXP-A2 , MaSUR14-like and MaXYL32. The transient overexpression of MaC2H2-like in 'Fenjiao' banana fruit promoted fruit ripening and softening by accelerating ethylene production, decreasing fruit firmness and inducing the transcription of starch and cell wall degradation-related genes. Collectively, we uncovered a novel module of MaC2H2-like-MaEBF1 that cooperates in actively impacting starch and cell wall degradation by up-regulating the transcript level of genes related to the degradation of starch and cell walls. [ABSTRACT FROM AUTHOR]

• Longan pericarp ontains high activity of browning related laccases (LACs). • LAC14-4 was purified from the pericarp and showed high activity to epicatechin. • LAC14-4 catalyzes (epi)catechin polymerization in vitro. • LAC14-4 is located in the vacuole and endoplasmic reticulum of the mesocarp cells. Polyphenol oxidase (PPO) has long been considered as the key enzyme responsible for the pericarp browning of longan fruit after harvest. However, due to the overlapping substrate ranges of PPOs and laccases, the contribution of laccases in longan pericarp browning is unclear. In this study, we found that the contents of flavan-3-ols and procyanidin A2/B2 in longan pericarp decreased during browning after harvest. It might be caused by high activity of laccases rather than PPOs. A 100-kDa laccase was purified from the pericarp and its protein sequence was identical to the deduced sequence of LAC14-4. The laccase showed more favored to (−)-epicatechin (EC) than other flavan-3-ols and procyanidin A2/B2 identified in the pericarp. Using EC and (+)-catechin (CT) as substrates, brown products were generated by LAC14-4 and exogenously expressed LAC14-4-3 × HA in vitro ; isomers of procyanidin polymers were detected in the products. Transient expression of LAC14-4-GFP in tobacco leaves showed that LAC14-4 was located in the vacuoles and endoplasmic reticulum. In situ hybridization showed that LAC14-4 mainly expressed in the outer part of mesocarp closed to the brachysclereid layer. The transcript, protein and activity levels of LAC14-4 in pericarp were upregulated during browning. In summary, longan pericarp contains high levels of LAC14-4 that catalyzes the procyanidin polymerization leading to longan pericarp browning. [ABSTRACT FROM AUTHOR]

Abstract: Banana (Musa AAA group) is one of the most consumed fruits in the world. It has been reported that chlorophyll breakdown and color formation in banana is inhibited by ripening temperatures above 24°C. At this temperature thylakoid membranes are retained resulting in reduced chlorophyll degradation. In this study, green mature, untreated banana fruit were obtained from a local wholesale market and half of the fruit were subjected to ethylene treatment at 10μLL−1 for 24d. After ethylene treatment, both treated and untreated fruit were stored at 20°C or 30°C for 7d. Fruit were sampled after 0, 1, 4 and 7d of storage and evaluated for color, chlorophyll fluorescence, volatile production and expression of genes related to volatile biosynthesis. Storage at 30°C reduced yellow color development in the peel, decreased chlorophyll fluorescence (Fv/Fm), but increased Fo, indicating possible heat stress of the fruit. A total of 19 volatile compounds were identified using SPME/GC/MS. Both ethylene treatment and high temperature enhanced volatile production. The increase of Fo and hexanoate and acetate esters are coincided with the stress of high temperature. Using real time PCR (qPCR), expression of genes related to volatile biosynthesis including branched-chain amino acid transaminase (BCAT), lipoxygenase (LOX), hydroperoxide lyase (HPL), pyruvate decarbolxylase (PDC), alcohol dehydrogenases (ADH, short and medium chains), and alcohol acetyl transferase (AAT) were investigated in both peel and pulp tissues. Among the tested genes, BCAT, HPL, ADH and AAT in peel and pulp tissues increased significantly in response to ethylene and storage at 30°C. PDC, ADH and BCAT (in pulp tissue) were induced by storage at 30°C in ethylene-treated fruit. LOX decreased during ripening and storage at 30°C in the peel, but increased in the pulp tissue of ethylene-treated fruit. This study demonstrates that both ethylene and high temperature influence volatile biosynthesis in banana fruit at the transcriptional level and confirms findings that high temperature causes stress in banana fruit during ripening. [Copyright &y& Elsevier]

Abstract: Chinese flowering cabbage is one of the main leafy vegetables produced in China. They have a rapid leaf yellowing due to chlorophyll degradation after harvest that limits their marketing. In the present study, leaf senescence of the cabbages was manipulated by ethylene and 6-benzyl aminopurine (6-BA) treatment to investigate the correlation of leaf senescence and chlorophyll degradation related to gene expression/activities in the darkness. The patterns of several senescence associated markers, including a typical marker, the expression of senescence-associated gene SAG 12 , demonstrated that ethylene accelerated leaf senescence of the cabbages, while 6-BA retarded this progress. Similar to the trends of BrSAG 12 gene expression, strong activation in the expression of three chlorophyll degradation related genes, pheophytinase (BrPPH), pheophorbide a oxygenase (BrPAO) and red chlorophyll catabolite reductase (BrRCCR), was detected in ethylene treated and control leaves during the incubation, while no evident increase was recorded in 6-BA treated leaves. The overall dynamics of Mg-dechelatase activities in all treatments displayed increasing trends during the senescence process, and a delayed increase in the activities was observed for 6-BA treated leaves. However, chlorophyllase activity as well as the expression of BrChlase1 and BrChlase2 decreased with the incubation in all treatments. Taken together, the expression of BrPPH, BrPAO and BrRCCR, and the activity of Mg-dechelatase was closely associated with the chlorophyll degradation during the leaf senescence process in harvested Chinese flowering cabbages under dark conditions. [Copyright &y& Elsevier]