Chinese flowering cabbage undergoes rapid leaf senescence, leading to quality deterioration and shortened shelf-life. Nitric oxide (NO) is known to delay postharvest leaf senescence in cabbages, yet its molecular mechanism remains largely unclear. Here, we demonstrated that NO treatment effectively delayed leaf yellowing, maintained higher chlorophyll content and Fv/Fm ratio, and suppressed the senescence-induced upregulation of BrMYB1R39 expression. BrMYB1R39, a 1R-MYB transcription factor, was a nuclear-localized transcriptional activator, and transient overexpression and silencing experiments confirmed its function as a positive senescence regulator. Moreover, DNA affinity purification sequencing (DAP-seq) revealed that BrMYB1R39 targeted a subset of starch and sugar metabolic genes. Subsequent electrophoretic mobility shift assay (EMSA) and dual-luciferase reporter (DLR) analyses verified that BrMYB1R39 activates BrAMY2, BrHXK3, BrBAM9, and BrSUS1 via directly binding to their promoters. By suppressing BrMYB1R39 expression, NO treatment attenuated BrMYB1R39’s activation on activities of sucrose synthase, hexokinase, α-amylase and β-amylase, thereby sustaining an elevated content of soluble sugars, glucose, fructose, sucrose and starch, and delaying leaf senescence. Our findings uncover a mechanistic link between NO and starch and sugar metabolism, identifying BrMYB1R39 as a potential candidate for extending shelf-life of leafy vegetables.

Leaf senescence after harvest limits the economic value of leafy cruciferous vegetables such as Chinese flowering cabbage (Brassica rapa ssp. parachinensis). Understanding the intricate gene regulatory networks that govern postharvest leaf senescence offers potential strategies to extend the shelf life of these vegetables. This study elucidated the regulatory networks modulating leaf senescence by utilizing time-series gene expression analysis on postharvest leaves of Chinese flowering cabbage treated with cytokinin analog 6-benzylaminopurine and abscisic acid (ABA). ABA treatment accelerated leaf senescence, including the dismantling of chloroplasts and mitochondria, whereas 6-benzylaminopurine treatment decelerated these processes. Subsequent RNA sequencing and integrated analyses led to the construction of transcriptional regulatory networks comprising 49 transcription factors potentially regulating senescence-related pathways, including reactive oxygen species (ROS) metabolism and chlorophyll degradation. Validation experiments on ROS metabolism confirmed that increased ROS accumulation paralleled the progression of leaf senescence, whereas ABA and 6-benzylaminopurine treatment resulted in opposing effects on ROS scavenging. Furthermore, exogenous ROS treatment promoted leaf senescence and the disassembly of chloroplasts and mitochondria, while ROS inhibitors delayed these processes. Further validation assays affirmed the expression patterns, transcription factor-binding capacities, and activation potentials of eight critical transcription factors and their possible target genes associated with ROS scavenging. Moreover, the role of two transcription factors (BrAGL42 and BrCRF11-2) in regulating postharvest leaf senescence and ROS scavenging ability was verified through transformation assays. Collectively, our findings shed light on the overarching transcription factor-mediated regulatory pathways in postharvest leaf senescence and indicate how cytokinin and ABA modulate this process antagonistically.

Ethylene-dependent softening is a crucial physiological process that influences the postharvest quality of banana fruit, with cell wall disassembly playing a key role in firmness loss. While the functions of several ripening-associated cell wall-modifying genes have been characterized, the regulatory mechanisms governing their expression are still mostly unknown. This study identified a transcriptional repressor, MaC3H33-like, which directly interacts with and suppresses the promoter of MaEXP1, an important cell wall-modifying gene involved in banana fruit softening. Moreover, MaC3H33-like interacts directly with a BOI-class E3 ubiquitin ligase, MaBRG3. Notably, MaBRG3 ubiquitinates MaC3H33-like to mediate ubiquitin-dependent degradation, thereby allowing the expression of MaEXP1 that promotes the fruit softening process. Collectively, these findings suggest that ethylene induces banana fruit softening presumably through the ubiquitin-dependent degradation of MaC3H33-like by MaBRG3, resulting in the activation of MaEXP1 gene expression and ultimately the softening of banana fruit. This study provides potential targets for the development of postharvest preservation technologies.

Litchi fruit are highly susceptible to browning during ambient storage, which results in a marked reduction in commercial value. This study investigated the regulatory effects and underlying mechanisms of alpha-ketoglutaric acid (AKG) on postharvest browning and senescence in litchi fruit. AKG treatment significantly reduced the browning index, delayed pigment degradation, and preserved cell membrane integrity. Moreover, AKG treatment alleviated the accumulation of reactive oxygen species (ROS) and enhanced antioxidant capacity. In parallel, AKG elevated the activities of key enzymes involved in the tricarboxylic acid (TCA) cycle, maintained high ATP levels and energy charge, and thereby provided sufficient energy to support ROS scavenging and cellular repair processes. Consequently, AKG synergistically improved both antioxidant capacity and energy metabolism. Transcriptomic analysis further revealed that AKG modulated the expression of genes associated with oxidoreductase activity, transmembrane transporter function, glycosyltransferase activity, and organic acid trans-membrane transporter activity. Specifically, AKG downregulated genes involved in browning and lignin synthesis (LcGOLS2, Lc4CL3, LcLAC14), ethylene signaling regulators (LcEIN4, LcERF4, LcERS1), and senescence regulators (LcNAC083, LcNAC090, LcNAC100, LcWRKY75, LcMYB73), while upregulating stress-responsive genes (LcTIFY9, LcbZIP44 and LcbHLH123). Collectively, these findings demonstrate that AKG delays postharvest browning and senescence in litchi by modulating ROS metabolism, enhancing TCA cycle-mediated energy production, and suppressing the expression of senescence-related genes.

Leaf yellowing caused by chlorophyll catabolism, is the most conspicuous trait of senescence in harvested leafy vegetables. Chlorophyll catabolism is a highly coordinated process primarily regulated by transcription factors (TFs). Therefore, identifying key TFs modulating chlorophyll catabolism is extremely important for understanding the regulatory networks of leafy vegetable yellowing. In this work, based on physiological and transcriptomic perspectives related to cytokinin (CTK) analogue 6-benzylaminopurine (6-BA)-delayed leaf yellowing, a weighted gene co-expression network analysis (WGCNA) was conducted to investigate possible TFs associated with chlorophyll catabolism regulation during senescence of harvested cabbages. A total of 327 TFs from 47 families were identified as candidate regulatory factors. Among these, a member of bZIP family BrTGA1-1 was focused. It was a nuclear-localized transcriptional activator and down-regulated by 6-BA. Further assays showed that it directly bound to the promoters of series chlorophyll catabolic genes (CCGs) including BrNYC1-1, BrNYC1-2, BrNOL and BrSGR1-2, thereby activating their transcription. Meanwhile, transient overexpression of BrTGA1-1 in tobacco leaves up-regulated CCGs expression, and facilitated chlorophyll catabolism, thus promoting leaf yellowing. In summary, BrTGA1-1 acts as an activator in accelerating leaf yellowing via upregulating CCGs, and our genome-wide identification of TFs regulating chlorophyll catabolism provides original insights into the regulatory networks for postharvest yellowing in leafy vegetables.

The journal retracts the article titled “Regulation of Long Non-Coding RNA-Dreh Involved in Proliferation and Migration of Hepatic Progenitor Cells during Liver Regeneration in Rats” [...]

Chlorophyll degradation, resulting in leaf yellowing, is a biomarker of leaf senescence and tightly controlled by multiple transcription factors (TFs) and epigenetic regulators. We previously identified a 6-BA (a synthetic cytokinin, CTK) inducible- while abscisic acid (ABA)-repressed Dof TF BrDof2.4 associated with leaf senescence in harvested Chinese flowering cabbage by suppressing the transcription of protease genes, however, the epigenetic modifications affecting BrDof2.4’s regulation have not been reported. Here we showed that the levels of histone H3 and H4 acetylation in the promoters of two chlorophyll catabolic genes (CCGs) BrSGR1 and BrNYC1 increased upon ABA while decreased by 6-BA during senescence. We further found that BrDof2.4 directly inhibited the transcription of BrSGR1 and BrNYC1 by binding to their promoters. Intriguingly, BrDof2.4 physically interacted with a histone deacetylase, BrHDA6, which possesses histone deacetylase activity. Moreover, this interaction significantly strengthened the BrDof2.4-mediated transcriptional inhibition of BrSGR1 and BrNYC1. Taken together, our findings suggest that BrDof2.4 can recruit BrHDA6 to co-repress the transcription of CCGs by affecting their acetylation levels, thereby involving in ABA-CTK-mediated leaf yellowing in postharvest Chinese flowering cabbage.

Litchi, a tropical and subtropical fruit with significant commercial value, is highly susceptible to browning and senescence after harvest. Dipeptides, the simplest form of peptides, play essential roles in various biological processes. However, their specific effects on litchi fruit browning and senescence remain unclear. This study demonstrated that Tyr-Asp treatment effectively delays browning of the litchi pericarp and maintained a higher proportion of marketable fruit. Tyr-Asp treatment inhibited the respiration rate, leading to reduced levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA), while increasing glutathione (GSH) content. Additionally, Tyr-Asp enhanced the activities of antioxidant enzymes, such as superoxide dismutase (SOD) and catalase (CAT), while suppressing the activity of peroxidase (POD) compared to the control group. Moreover, Tyr-Asp treatment improved the NADPH/NADP* ratio without affecting the NADH/NAD* ratio. Energy status analysis revealed that Tyr-Asp notably increases the energy charge (EC) compared to the control group, suggesting enhanced energy homeostasis. RT-qPCR analysis showed that Tyr-Asp reduces the expression of energy metabolism-related genes (UCP1, GAPDH) and PPO, while simultaneously upregulating key genes involved in antioxidant defense, energy metabolism, and stress response, including SOD, CAT, APX1, POD2, DHAR, MDHAR, SnRK2, AtpB, and AAC1. These changes collectively contributed to the delayed browning and senescence of litchi fruit. Overall, these findings indicated that Tyr-Asp alleviates browning and delays senescence in litchi fruit by modulating key metabolic pathways, thereby enhancing redox balance and optimizing energy homeostasis.

Banana fruit is highly vulnerable to chilling injury (CI) during cold storage, which results in quality deterioration and commodity reduction. Dipeptides, the simplest form of peptides, play a vital role in numerous essential biological processes. However, their specific impact on banana fruit CI remains unclear. This study demonstrates that applying Tyr-Asp effectively reduces CI in banana, resulting in lower levels of H2O2and MDA, while increasing GSH content. Tyr-Asp treatment enhances the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), while decreasing polyphenol oxidase (PPO) activity compared to the control group. Furthermore, Tyr-Asp improves the NADPH/NADP* ratio without affecting the NADH/NAD* ratio. Transcriptome analysis reveals that Tyr-Asp upregulates genes associated with primary metabolic processes, stimulus response, oxidative phosphorylation, oxidoreductase activity, and transcriptional regulation, while downregulating genes related to catalytic activity, phosphorus metabolism, oxyacid metabolism, lipid metabolism, and ATP hydrolysis. RT-qPCR results confirm that Tyr-Asp treatment reduces the expression of LOX1.1, LOX1.4, and PPO, while increasing the expression of SOD, CAT, POD, HSP22, HSP70, GAPN, GAPB, MYC2, MYB78, WRKY6, and WRKY30, thereby contributing to redox balance and enhancing cold resistance in banana fruit. These findings suggest that Tyr-Asp mitigates CI in banana fruit by modulating metabolic shifts through the regulation of key functional genes and transcription factors.

Banana fruit easily develop chilling injury (CI) when stored at inappropriate low temperatures for extended periods. Hydrogen sulfide (H2S) has been shown to attenuate CI in banana fruit, but the mechanism underlying how H2S enhances chilling tolerance remains largely elusive. In this study, we discovered MaWRKY45, whose expression was highly elevated by the H2S donor NaHS, based on transcriptome analysis related to NaHSmitigating CI in banana fruit. MaWRKY45 is a nucleus-localized protein with transcriptional activation properties. Moreover, MaWRKY45 targets not only the ROS-scavenging genes MaPOD3 and MaGSTU18 but also binds to the promoters of MaERF53L/121 L, two important regulators of chilling tolerance affected by NaHS treatment, thereby activating their transcription. Importantly, MaWRKY45 interacts with MaERF53L/121 L to form protein complex, further increasing the transcription of MaPOD3 and MaGSTU18. These results reveal that MaWRKY45 partakes in H2S-attenuated CI in banana fruit directly by activating ROS-scavenging gene expression, and indirectly by interacting with the promoters and proteins of the chilling regulators MaERF53L/121 L. This work expands the current model of H2S-ameliorated CI in banana fruit and provides evidence for the roles of WRKY in the regulation of low-temperature stress.

Fruit ripening depends on the accurate control of ripening-related genes expression, with histone deacetylases (HDACs) playing crucial roles in transcriptional regulation. However, the functions of HDACs in fruit maturation remain largely unexplored. Here, we show that SlHDA7 acts as a suppressor of fruit ripening and functions as an H4ac HDAC in tomato. Deletion of SlHDA7 accelerated fruit ripening, while overexpression of SlHDA7 delayed the maturation process. Additionally, ethylene production and carotenoid biosynthesis significantly increased in slhda7 mutant fruits but decreased in SlHDA7-overexpressing fruits. Furthermore, SlHDA7 repress the expression of ethylene production and signaling, carotenoid metabolism, cell wall modification, and transcriptional regulation-related genes. RT-qPCR and ChIP-qPCR analyses indicated that SlHDA7 may deacetylate H4ac, leading to reduced transcript levels of ACO1, GGPPS2, Z-ISO, EXP1, and XYL1 mRNA, consequently suppressing fruit ripening. Moreover, SlHDA7 suppresses fruit ripening by targeting specific ripening-associated transcription factors (TFs) like RIN, FUL1, and ERF.E1, ultimately leading to delayed ripening and prolonged fruit shelf life. In summary, our findings indicate that SlHDA7 negatively modulates tomato fruit maturation by adjusting H4ac levels of these ripening-associated genes and key TFs.

The synthetic cytokinin (CTK) 6-benzylaminopurine (6-BA), known to inhibit chlorophyll degradation, effectively retards leaf senescence in various horticultural crops. Although extensively implicated in root growth, shoot development, and abiotic stress response, the role of type-B ARRs in leaf senescence regulation remains relatively understudied. Hence, the involvement and mechanistic contribution of type-B ARR proteins in 6-BA-induced delay of postharvest leaf senescence in Chinese flowering cabbage merits closer investigation. In the present study, exogenous 6-BA treatment notably mitigated the decline in maximum quantum yield (Fv/Fm) and total chlorophyll content, as well as the expression of chlorophyll catabolic genes BrPPH1, BrNYC1 and senescence-associated gene BrSAG12 during Chinese flowering cabbage storage. Importantly, BrARR10, a type-B cytokinin response regulator, was induced by 6-BA treatment. Further, BrARR10 was characterized as a nuclear-localized transcriptional activator. Moreover, DAP-seq analysis identified BrARR10’s potential target genes, which predominantly function within the phytohormone signal transduction pathway. EMSA, ChIP-qPCR and DLR assays revealed that BrARR10 directly bound the promoters of CTK biosynthesis genes (BrIPT5, BrLOG3), GA biosynthesis genes (BrGA20ox1, BrGA20ox3), and ABA catabolism genes (BrCYP707A1, BrCYP707A3) in vitro and in vivo, simultaneously activating their expression. Additionally, leaves of transgenic Arabidopsis overexpressing BrARR10 displayed increased expression of these genes, resulting in a delayed senescence phenotype. Overall, the novel 6-BA-ARR model in this study contributes a new insight into the transcriptional regulatory mechanisms underlying 6-BA-mediated plant leaf senescence and furnishing a new theoretical foundation for understanding plant hormone interaction in postharvest preservation.

Texture softening is a physiological indicator of fruit ripening, which eventually contributes to fruit quality and the consumer’s acceptance. Despite great progress having been made in identification of the genes related to fruit softening, the upstream transcriptional regulatory pathways of these softening-related genes are not fully elucidated. Here, a novel bHLH gene, designated as MabHLH28, was identified because of its significant upregulation in banana fruit ripening. DAP-Seq analysis revealed that MabHLH28 bound to the core sequence of ‘CAYGTG’ presented in promoter regions of fruit softening-associated genes, such as the genes related to cell wall modification (MaPG3, MaPE1, MaPL5, MaPL8, MaEXP1, MaEXP2, MaEXPA2, and MaEXPA15) and starch degradation (MaGWD1 and MaLSF2), and these bindings were validated by EMSA and DLR assays. Transient overexpression and knockdown of MabHLH28 in banana fruit resulted in up- and down-regulation of softening-related genes, thereby hastening and postponing fruit ripening. Furthermore, overexpression of MabHLH28 in tomato accelerated the ripening process by elevating the accumulation of softening-associated genes. In addition, MabHLH28 showed interaction withMaWRKY49/111 and itself to form protein complexes, which could combinatorically strengthen the transcription of softening-associated genes. Taken together, our findings suggest that MabHLH28 mediates fruit softening by upregulating the expression of softening-related genes either alone or in combination with MaWRKY49/111.

ATP is the primary form of energy for plants, and a shortage of cellular ATP is generally acknowledged to pose a threat to plant growth and development, stress resistance, and crop quality. The overall metabolic processes that contribute to the ATP pool, from production, dissipation, and transport to elimination, have been studied extensively. Considerable evidence has revealed that in addition to its role in energy supply, ATP also acts as a regulatory signaling molecule to activate global metabolic responses. Identification of the eATP receptor DORN1 contributed to a better understanding of how plants cope with disruption of ATP homeostasis and of the key points at which ATP signaling pathways intersect in cells or whole organisms. The functions of SnRK1α, the master regulator of the energy management network, in restoring the equilibrium of the ATP pool have been demonstrated, and the vast and complex metabolic network mediated by SnRK1α to adapt to fluctuating environments has been characterized. This paper reviews recent advances in understanding the regulatory control of the cellular ATP pool and discusses possible interactions among key regulators of ATP-pool homeostasis and crosstalk between iATP/eATP signaling pathways. Perception of ATP deficit and modulation of cellular ATP homeostasis mediated by SnRK1α in plants are discussed at the physiological and molecular levels. Finally, we suggest future research directions for modulation of plant cellular ATP homeostasis.

Energy status of cells is a key factor in switching on the senescence process of horticultural crops. Extracellular ATP (eATP) and its receptor DORN1 play pivotal roles in responding to energy deficit signals and are involved in multiple biological processes, yet their mechanisms remain unclear. A total of 17 LcDORN1 genes were identified in the genome of litchi. During storage of litchi fruit, eATP gradually acummulated with the upregulated expression of LcDORN1s. However, this trend was delayed by the application of exogenous ATP, ultimately leading to delayed senescence of the litchi fruit. LcDORN1.2 and LcDORN1.6, which were verified to be localized in the endoplasmic reticulum, were specifically targeted and modulated by LcmiR3627f and LcmiR159b, respectively. The expression of LcPLD was upregulated, whereas the expression of LcAPY1 was downregulated in LcDORN1.6 silenced litchi fruit. This research provides novel insights into the roles of eATP and its receptor, LcDORN1s, in the ripening and senescence of litchi fruit.

In this study, the impact of modified atmosphere packaging (MAP) on quality, lignin biosynthesis, reactive oxygen species (ROS) metabolism, and microstructures of stem in Chinese flowering cabbages was investigated. Compared with control, MAP treatment retained higher content of protein, total soluble solid, and vitamin C, while lower weight loss rate, carbon dioxide (CO2) production rate, electrolyte leakage, firmness and hollowing of stems. Lignin content in MAP-treated stems was 1.23-fold higher than that of control stems on the twelfth day. Moreover, MAP treatment inhibited the increasing in cell wall thickness by inhibiting activities of lignin biosynthesis-related enzymes. In addition, MAP suppressed ROS contents, while enhanced levels of ascorbic acid and reduced glutathione through promoting activities of antioxidant enzymes. The above results suggest that maintaining stems quality of Chinese flowering cabbages through MAP treatment is related to prevent lignin accumulation around the vascular tissue and enhance antioxidant capacity.

Chinese flowering cabbage has a limited shelf-life because of rapid leaf senescence and serious quality deteri-oration. Modified atmosphere packaging (MAP) is an effective technology used to preserve fresh vegetables. However, its underpinning mechanism is largely unknown. This study found that MAP prevented the decline in chlorophyll loss and Fv/Fm ratio, and kept higher levels of soluble sugars, total phenols and flavonoids, remarkably dampening leaf senescence and maintaining quality of harvested Chinese flowering cabbage. Moreover, in total, 575 differentially accumulated metabolites (DAMs) and 12,470 differentially expressed genes (DEGs) were obtained. Additionally, 151 transcription factors (TFs) were significantly differentially expressed. Importantly, we further developed complex regulatory networks incorporating crucial structural genes and TFs contributing to metabolism of chlorophyll, soluble sugars, amino acids, phenolic acids and flavonoids in post-harvest Chinese flowering cabbage. Above all, our findings provide new insights into the regulatory pathways of MAP-maintained leaf quality in postharvest Chinese flowering cabbage.

β-胡萝卜素羟化酶是类胡萝卜素合成代谢途径中的关键酶,可以将合成代谢途径中产生的含β-环的类胡萝卜素转化成β-隐黄素和玉米黄素.利用同源克隆技术获得桃果实B-胡萝卜素羟化酶(HYb)基因的全长核苷酸序列,命名为PpHYb.PpHYb基因全长1 405 bp,编码区长933 bp,共编码翻译成310个氨基酸.进化树分析发现PpHYb与草莓FaHYb亲缘性较高.序列分析发现PpHYb与其他物种中的HYb 一样,同样含有模体为"HXXXXH"+"HXXHH"的保守基序.实时荧光定量PCR结果显示PpHYb基因在黄肉品种'金丽'桃果实软核期、硬核期、膨大期、硬熟期和完熟期中均有表达.当果实处于硬熟期之前时,PpHYb基因在果皮和果肉中的表达逐渐升高并达到最大值;当果实处于完熟期时,PpHYb基因在果皮和果肉中的表达略有下降,且在果皮中的表达显著高于果肉.本研究通过对桃果中PpHYb基因的克隆和表达分析,为进一步研究类胡萝卜素生物合成途径提供了基础.

Banana is a good source of carotenoids, which are bioactive metabolites with health beneficial properties for human. However, the molecular mechanism of carotenoid accumulation in banana fruit is largely unclear. In this study, we found that high temperature elevated carotenoid production in banana pulp, which is presumably due to upregulation of a subset of carotenogenic genes as well as a carotenoid biosynthesis regulator MaSPL16. Moreover, an ethylene signaling component MaEIL9 was identified, whose transcript and protein contents were also induced by high temperature. In addition, MaEIL9 positively regulates transcription of MaDXR1, MaPDS1, MaZDS1 and MaSPL16 through directly targeting their promoters. Overexpression of MaEIL9 in tomato fruit substantially increased the expression of carotenoid formation genes and elevated carotenoid content. Importantly, transiently silencing MaEIL9 in banana fruit weakened carotenoid production caused by high temperature. Taken together, these results indicate that high temperature induces carotenoid production in banana fruit, at least in part, through MaEIL9-mediated activation of MaDXR1, MaPDS1, MaZDS1 and MaSPL16 expression.