Plant Science

BackgroundDark-induced senescence (DIS) is a widely used model for dissecting the regulatory mechanisms that manage leaf aging, redox imbalance, and cell death (CD) in plants. Salicylic acid (SA) is a central hormonal regulator of these processes. However, the mechanism involving upstream components, which integrate SA-dependent pathways with antioxidant homeostasis during DIS, remains unresolved. CYSTEINE-RICH RECEPTOR-LIKE KINASE 5 (CRK5) is a membrane-localized protein that plays a role in developmental and stress-responsive pathways. Its promoter contains multiple W-box cis-elements, indicating regulation by WRKY factors in SA-mediated pathways. This study investigates how CRK5 modulates SA-dependent CD and antioxidant dynamics during DIS. ResultsIn this study, SA-accumulating mutant crk5 exhibited accelerated senescence, elevated electrolyte leakage, enhanced micro-lesion formation, and markedly increased reactive oxygen species (ROS) accumulation under both control and dark conditions. These phenotypes were accompanied by a substantial reduction in carotenoid and xanthophyll pools, enhanced accumulation of phenolic compounds, and increased free radical scavenging capacity, including ascorbate peroxidase, catalase, and superoxide dismutase activities. Importantly, crk5 phenotype was fully reverted in crk5sid2 and crk5NahG double mutants, confirming that crk5 DIS phenotype is induced by activation of the SA-signaling pathway. Transcriptome profiling revealed extensive deregulation of senescence-, CD-, and redox-associated genes in crk5 during darkness, including strong induction of SAGs, metacaspases, autophagy, and antioxidant-related transcripts. The line with constitutively enhanced SA level (cpr1), used as a control, showed similar phenotypes to crk5, although transcriptional reprogramming was largely absent in cpr1 after darkness, highlighting CRK5 as a key upstream negative regulator of SA-mediated CD and positive regulator of antioxidant homeostasis. ConclusionOur work presents CRK5 as a central regulatory hub that inhibits the SA-signaling, ROS burst, and CD activation during DIS. Loss of CRK5 function is associated with the activation of SA-signaling, altered antioxidant systems, increased ROS burden, and ROS-driven CD acceleration, resulting in accelerated senescence. Conversely, suppression of SA-biosynthesis or -catabolism in a crk5 background restores the wild-type phenotype. These findings position this receptor kinase as a key mediator that coordinates hormonal, metabolic, and oxidative pathways to maintain leaf viability, providing mechanistic insight into the control of stress-induced senescence and CD in Arabidopsis.

Enzymatic browning significantly affects the appearance and quality of fresh-cut fruit. Light treatment can effectively inhibit fresh-cut apple browning via unknown molecular mechanisms. Here, we found that the application of purple LED light decreased the browning index of fresh-cut apple, delaying browning as compared to that of fresh-cut apple placed in the dark, and suggesting that purple LED light suppresses browning. In addition, the expression levels of MdHY5 and MdHY5S, important BASIC LEUCINE ZIPPER DOMAIN (bZIP) transcription factors that are involved in the light signaling pathway, were increased by purple LED light treatment. Silencing MdHY5 and MdHY5S in apple meant that purple LED light treatment no longer inhibited fresh-cut apple browning, the expression levels of the browning-related genes POLYPHENOL OXIDASE (MdPPO) and PEROXIDASE (MdPOD) increased, and the expression of the phenolic synthesis gene PHENYLALANINE AMMONIALYASE (MdPAL) decreased. Further study revealed that MdHY5 and MdHY5S bind to the MdPPO and MdPOD promoters, reducing their transcription. In contrast, MdHY5 and MdHY5S bind to the MdPAL promoter, enhancing transcription. Further research revealed that MdHY5 and MdHY5S also bind directly to each others promoters to form a positive transcriptional loop that activates their transcription. Our findings revealed that purple LED light inhibits browning and increases phenolics synthesis in fresh-cut apple by activating MdHY5 and MdHY5S. The results provide a theoretical basis upon which the new methods for improving the appearance and quality of fresh-cut apple can be based.

Proline is a key compound that lowers cell water potential, scavenges reactive oxygen species, and stabilizes biomolecules and cell membranes, thus reducing stress-induced damage. Proline dehydrogenase (ProDH), the first rate-limiting enzyme in proline degradation, plays a crucial role in proline accumulation. We explored the role of the GhProDH gene family in regulating physiological responses to stress conditions through transcriptome, metabolome and functional analyses. Overexpression and gene silencing lines in Arabidopsis and cotton revealed that GhProDH2 plays a key role in regulating cottons tolerance to drought and salt stress. GhProDH2-4 improves cottons tolerance to drought and salt stress by engaging in carbon metabolism, glyoxylate cycle, and flavonoid metabolism pathways. These findings highlight the potential role of GhProDH2-4 to improve cotton stress resistance by genetically modifying pathways involved in proline biosynthesis and degradation.

The role of the cytosolic O-acetylserine-(thiol) lyase A (OASTLA), chloroplastic OASTLB and mitochondrion OASTLC in plant resistance/sensitivity to selenate was studied in Arabidopsis plants. Impairment in OASTLA and B resulted in reduced biomass, chlorophyll and soluble protein levels compared with impaired OASTL C and Wild-Type treated with selenate. The lower organic-Se and protein-Se levels followed by decreased organic-S, S in proteins and total glutathione in oastlA and oastlB compared to Wild-Type and oastlC are indicative that Se accumulation is not the main cause for the stress symptoms, but rather the interference of Se with the S-reduction pathway. The increase in sulfite oxidase, adenosine 5'-phosphosulfate reductase, sulfite reductase and OASTL activity levels, followed by enhanced sulfite and sulfide, indicate a futile anabolic S-starvation response to selenate-induced organic-S catabolism in oastlA and oastlB compared to Wild-Type and oastlC. Additionally, the catabolic pathway of L-cysteine degradation was enhanced by selenate, and similar to L-cysteine producing activity, oastlA and B exhibited a significant decrease in L-cysteine desulfhydrase (DES) activity, compared with WT, indicating a major role of OASTLs in L-cysteine degradation. This notion was further evidenced by sulfide dependent DES in-gel activity, immunoblotting, immunoprecipitation with specific antibodies and identification of unique peptides in activity bands generated by OASTLA, B and C. Similar responses of the OASTLs in Seleno-Cysteine degradation was demonstrated in selenate stressed plants. Notably, no L-cysteine and L-Seleno-Cysteine DES activity bands but those related to OASTLs were evident. These results indicate the significance of OASTLs in degrading L-cysteine and L-SelenoCysteine in Arabidopsis. SummaryThe cytosolic OASTLA and chloroplastic OASTLB have significantly higher desulfhydrase activity rates than the cytosolic DES1 and are able to degrade L-Cys and L-SeCys to sulfide and selenide, respectively in Arabidopsis.

Among the three active aldehyde oxidases in Arabidopsis thaliana leaves (AAO1-3), AAO3, which catalyzes the oxidation of abscisic-aldehyde to abscisic-acid, was shown recently to function as a reactive aldehyde detoxifier. Notably, aao2KO mutants exhibited less senescence symptoms and lower aldehyde accumulation, such as acrolein, benzaldehyde, and HNE than in wild-type leaves exposed to UV-C or Rose-Bengal. The effect of the absence of AAO2 expression on aldehyde detoxification by AAO3 and/or AAO1 was studied by comparing the response of wild-type plants to the response of aao1Single mutant, aao2KO mutants and single mutants of aao3Ss. Notably, aao3Ss exhibited similar aldehyde accumulation and chlorophyll content to aao2KO treated with UV-C or Rose-Bengal. In contrast, wild-type and aao1S exhibited higher aldehyde accumulation that resulted in lower remaining chlorophyll than in aao2KO leaves, indicating that the absence of active AAO2 enhanced AAO3 detoxification activity in aao2KO mutants. In support of this notion, employing abscisic-aldehyde as a specific substrate marker for AAO3 activity revealed enhanced AAO3 activity in aao2KO and aao3Ss leaves compared to wild-type treated with UV-C or Rose Bengal. The similar abscisic acid level accumulated in leaves of unstressed or stressed genotypes indicates that aldehyde detoxification by AAO3 is the cause for better stress resistance in aao2KO mutants. Employing the sulfuration process (known to activate aldehyde oxidases) in wild-type, aao2KO, and molybdenum-cofactor sulfurase (aba3-1) mutant plants revealed that the active AAO2 in WT employs sulfuration processes essential for AAO3 activity level, resulting in the lower AAO3 activity in WT than AAO3 activity in aao2KO.

Ribonucleotide reductase (RNR), functioning in the de novo synthesis of dNTPs, is crucial for DNA replication and cell cycle progression. However, the knowledge about the RNR in plants is still limited. In this study, we isolated ylc1 (young leaf chlorosis 1) mutant, which exhibited many development defects such as dwarf stature, chlorotic young leaf, and smaller fruits. Map-based cloning, complementation, and knocking-out experiments confirmed that YLC1 encodes a large subunit of RNR (SlRNRL1), an enzyme involved in the de novo biosynthesis of dNTPs. Physiological and transcriptomic analyses indicate that SlRNRL1 plays a crucial role in the regulation of cell cycle, chloroplast biogenesis, and photosynthesis in tomato. In addition, we knocked out SlRNRL2 (a SlRNRL1 homolog) using CRISPR-Cas9 technology in the tomato genome, and found that SlRNRL2, possessing a redundant function with SlRNRL1, played a weak role in the formation of RNR complex due to its low expression intensity. Genetic analysis reveals that SlRNRL1 and SlRNRL2 are essential for tomato growth and development as the double mutant slrnrl1slrnrl2 is lethal. This also implies that the de novo synthesis of dNTPs is required for seed development in tomato. Overall, our results provide a new insight for understanding the SlRNRL1 and SlRNRL2 functions and the mechanism of de novo biosynthesis of dNTPs in plants.

Seed longevity is a key determinant of crop establishment, productivity, and germplasm conservation. During storage and germination, reactive oxygen species accumulate and contribute to seed aging through oxidative damage and loss of viability. The maintenance of redox homeostasis therefore relies on NADPH-dependent antioxidant systems, which require a continuous supply of reducing power. NADP-dependent malic enzyme 1 (NADP-ME1), represents a source of NADPH supporting antioxidant defense during seed aging. Here, we show that enhanced expression of NADP-ME1 positively contributes to seed vigor and longevity in Arabidopsis thaliana. NADP-ME1 overexpression lines exhibited faster germination and higher overall germination after accelerated aging, whereas knockout mutants showed markedly reduced germination performance. Enhanced post-aging vigor in the overexpression lines was associated with reduced oxidative damage as indicated by lower malondialdehyde and hydrogen peroxide accumulation, along with preservation of specific polyunsaturated fatty acids, and increased {gamma}-tocopherol levels in aged dry seeds. Enhanced expression of NADP-ME1 reshapes the transcriptome of germinated seeds under fresh conditions compared with the wild type, while only minimal differences between genotypes are detected in aged seeds. These results suggest that NADP-ME1 contributes to the establishment of a transcriptional state associated with enhanced seed vigor and improved post-aging germination. Finally, co-immunoprecipitation coupled to mass spectrometry and bimolecular fluorescence complementation identified aspartate aminotransferase 2 as a NADP-ME1 interactor, pointing to a link between malate metabolism and amino acid-related metabolic adjustment. Together, these results identify NADP-ME1 as a determinant of seed resilience to aging and a potential target for improving seed quality.

Glutaredoxins (Grxs) are small, ubiquitous, multi-functional proteins present in different compartments of plant cells. A chloroplast targeted class I GRX (CcGRXS12) gene was isolated from Capsicum chinense during the pepper mild mottle virus (PMMoV) infection. Functional characterization of the gene was performed in N. benthamiana transgenic plants transformed with native C. chinense GRX (Nb:GRX), GRX-fused with GFP (Nb:GRX-GFP) and GRX truncated for the chloroplast targeting sequences but fused with GFP (Nb:{Delta}2MGRX-GFP). Over-expression of CcGRXS12 inhibits the PMMoV-I accumulation at late stage of infection and is accompanied with the activation of SA- pathway pathogenesis related (PR) transcripts, and suppression of JA/ET- pathway transcripts. Further the reduced accumulation of auxin-induced Glutathione-S-Transferase (pCNT103) in CcGRXS12 over expressing lines indicates that the protein could able to protect the plants from the oxidative stress caused by the virus. PMMoV-I infection increases accumulation of pyridine nucleotides (PNs) mainly due to the reduced form of PNs (NAD(P)H) and it was higher in Nb:GRX-GFP lines compared to other lines where infection is limited. Apart from biotic stress, CcGRXS12 protects the plants from abiotic stress conditions caused by H2O2 and herbicide paraquat. CcGRXS12 exhibits GSH-disulphide oxidoreductase activity in vitro however devoid of complementary Fe-S cluster assembly mechanism in yeast.

In the model plant Arabidopsis thaliana, parental age is known to affect somatic mutation rates in their immediate progeny and here we show that this age dependent effect persists across successive generations. Using a set of detector lines carrying the mutated uidA gene, we examined if a particular parental age maintained across five consecutive generations affected the rates of base substitution (BSR), intrachromosomal recombination (ICR), frameshift mutation (FS), and transposition. The frequency of functional GUS reversions were assessed in seedlings as a function of identical/different parental ages across generations. In the context of a fixed parental age, BCR/ICR rates were unaffected in the first three generations, then dropped significantly in the 4th and increased in most instances in the 5th generation. On the other hand, with advancing parental ages, BSR/ICR rates remained high in the first two/three generations, with a striking resemblance in the pattern of mutation rates. We adopted a novel approach of identifying and tagging flowers pollinated on a particular day, thereby avoiding biases due to potential emasculation induced stress responses. Our results suggest a time component in counting the number of generations a plant has passed through self-fertilization at a particular age in determining the somatic mutation rates.

RAP2.6, an AP2/ERF transcription factor (TF), regulates plant stress responses; however, its role in floral transition remains unexplored. Here, we evaluated RAP2.6s role in flowering and the associated transcriptional changes in Arabidopsis thaliana under long-day conditions. RAP2.6-overexpressing line showed early flowering with fewer rosette leaves, whereas rap2.6-1 mutant flowered later, had more rosette leaves, and higher expression of the floral repressor FLOWERING LOCUS C (FLC). Early flowering in the overexpressing line was accompanied by transcriptional activation of the floral integrators GIGANTEA (GI), FLOWERING LOCUS T (FT), and COSTANS (CO), potentially through RAP2.6 interaction with GCC/DRE cis-regulatory elements. RAP2.6-mediated floral transition depended on nitric oxide (NO), with flowering time largely varying based on NO bioactivity. RAP2.6 was found to be a downstream regulator of Arabidopsis S-NITROSOGLUTATHIONE REDUCTASE 1 (GSNOR1) in controlling S-nitrosothiol (SNO) levels, flowering time, and silique formation. The NITRIC OXIDE-ASSOCIATED 1 (NOA1)-dependent reduction in NO levels abolished early flowering in 35S::RAP2.6 plants without affecting silique formation. Furthermore, enhanced cytokinin sensitivity and upregulation of cytokinin biosynthetic genes suggest cytokinin involvement in RAP2.6-mediated flowering. Together, these findings highlight the crucial role of RAP2.6 in regulating flowering time by integrating redox and hormonal signaling to coordinate reproductive development in A. thaliana.

Abscisic acid (ABA) plays a vital role in coordinating physiological processes during fresh fruit ripening. ABA can bind to ABA receptors which interacts and inhibits their co-receptors type 2C phosphatases (PP2Cs). However, the dissected mechanism of PP2C during fruit ripening is unclear. In this study, we identify the role of SlPP2C3, a tomato type 2C phosphatase, as a negative regulator of ABA signaling and fruit ripening. SlPP2C3 selectively interacted with monomeric ABA receptors and SlSnRK2.8 kinase in both yeast and tobacco epidermal cells. Expressions of SlPP2C3 were observed in all tissues, and it negatively correlated with the fruit ripening which was induced by exogenous ABA. Tomato plants with suppressed SlPP2C3 expression exhibited enhanced sensitivity to ABA, while SlPP2C3 over-expressed plants were less sensitive to ABA. Meaningfully, lack of SlPP2C3 expression causes the acceleration of fruit ripening onset via the alternation of ABA signaling activity, and the fruit gloss is affected by the changes of outer epidermis structure. RNA-seq analysis found significant different expression of cuticle-related genes in pericarp between wild-type and SlPP2C3 suppressed lines. Taken together, our finding demonstrate that SlPP2C3 plays an important role in the regulation of fruit ripening and fruit appearance quality in tomato.

DNA methylation plays a crucial role in regulating fruit ripening and seed development. It remains unknown about the dynamic characteristics of DNA methylation and its regulation mechanisms in morpho-physiological dormancy (MPD)-typed seeds with recalcitrant characteristics. The P. notoginseng seeds are defined by the MPD and are characterized by a strong sensitivity to dehydration during the after-ripening process. We performed DNA methylomes, siRNA profiles, and transcriptomes of embryo and endosperm in P. notoginseng seeds at different after-ripening stages. Herein, we find that the CHH hyper-methylation contributes to the global increase in DNA methylation during the after-ripening process of P. notoginseng seeds. The endosperm genome is hyper-methylated compared to the embryo genome. The CHH hyper-methylation is caused by the high expression level of DNA methyltransferase PnCMT2 in the embryo, and PnDRM2 in the endosperm, respectively. The CHH hyper-methylation alters gene transcription levels to regulate the after-ripening and dormancy of recalcitrant seeds. For example, it inhibits the expression of genes in embryo development to make seeds maintain a dormant status, whereas it activates the expression of genes in the hormone-mediated signaling pathway, and energy metabolism to accomplish the MPD-typed seed after-ripening process. Together, our findings reveal a global increase in DNA methylation and its vital driver in gene expression, and thus elucidate how global CHH hyper-methylation regulates the after-ripening in recalcitrant MPD-typed seeds. This work establishes a key role for epigenetics in regulating the dormancy of MPD-typed seeds with recalcitrant characteristics.

Strigolactones (SLs) are an important class of plant hormones that play crucial roles in regulating plant branching, root architecture, and organ development. However, the regulatory mechanisms underlying the crosstalk between SLs and other plant hormones remain largely unclear, particularly regarding the key regulatory genes that integrate and coordinate multiple hormonal signaling pathways. In this study, secondary cup seedlings of the Pisang Awak banana cultivar Yufen 6 at the eight-leaf stage were used as experimental materials. The roots were treated with a nutrient solution containing 30 mol/L exogenous SLs, while a nutrient solution supplemented with water served as the control. Tissues near the corm growth point were collected at 0, 15, 30, 60, 90, and 120 days after treatment to measure corm weight, height, and diameter, and transcriptome sequencing was performed using the collected tissues. Differentially expressed genes (DEGs) at different treatment stages were identified, followed by Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses to systematically investigate the crosstalk between SLs and endogenous hormone metabolism and signaling during corm development in Pisang Awak banana. The results showed that SL treatment significantly inhibited the weight, height, and diameter of the corm. The regulatory effect of SLs on Pisang Awak banana corm development exhibited a clear temporal dynamic pattern, representing a gradual accumulation process that ultimately triggers key developmental transitions. The highest number of DEGs was detected at 15 days after treatment, including 3943 upregulated genes and 3704 downregulated genes, indicating that this stage represents a critical phase for SL response initiation. GO enrichment analysis revealed that the DEGs were mainly involved in metabolic processes, biological regulation, response to stimulus, and regulation of biological processes. KEGG pathway analysis indicated that these DEGs were significantly enriched in pathways related to plant hormone signal transduction, starch and sucrose metabolism, and secondary metabolite biosynthesis. Further analysis revealed that the crosstalk between SLs and multiple hormone metabolic and signaling pathways is mediated by the SPL15 gene, involving auxin (IAA), cytokinin (CTK), abscisic acid (ABA), brassinosteroids (BRs), gibberellins (GA), and jasmonic acid (JA) pathways. This study reveals the molecular mechanism by which SLs regulate Pisang Awak banana corm development through SPL15-mediated integration of multiple hormonal signals, providing new insights into the role of SLs in regulating the development of underground organs in banana.

ADP-ribosylation mediated by ADP-ribosyltransferases (ARTs) is an intricate modification that regulates diverse cellular processes including DNA repair, chromatin remodeling and gene transcription responding to stresses. In addition to the canonical poly(ADP-ribose) polymerases (PARPs), plant specific SRO (Similar to RCD One) family also contain the catalytic core of the PARP domain. However, whether the PARP domains in SROs execute the ART function is still under debate. In 2014, we reported a wheat SRO, Ta-sro1, had the ADP-ribosyltransferase activity and enhanced wheat seedling growth and abiotic stress resistance, however, a recent work by Vogt et al. showed that Ta-sro1 without ADP-ribosyltransferase activity. Based on the recent progress on PARPs and SROs in relation to ADP-ribosyltransferase activity, along with our former and recent evolving results, we argued that Ta-sro1 is a non-canonical ADP-ribosyltransferase with the enzymatic activity. Although we have revealed the novel mechanism of Ta-sro1 regulate redox homeostasis and enhance salinity stress tolerance through interacting with TaSIP1, it is of interest to further clarify whether and how the enzymatic activity of Ta-sro1 responsible for the salinity tolerance of wheat. Our study raises some interesting points and caveats that helpful for understanding the research progresses and debates about the enzymatic activity of SROs.

The role of sirtuins in plants are slowly unraveling. There are only reports of H3K9Ac deacetylation by OsSRT1. Here our studies shade light on its dual enzyme capability with preference for mono ADP ribosylation over deacetylation. OsSRT1 can specifically transfer the single ADP ribose group on its substrates in an enzymatic manner. This mono ADPr effect is not well known in plants, more so for deacetylases. The products of this reaction (NAM and ADP ribose) have immense negative effect on this enzyme suggesting a tighter regulation. Resveratrol, a natural plant polyphenol proves to be a strong activator of this enzyme at 150 M concentration. Under different abiotic stress conditions, we could link this ADP ribosylase activity to the DNA repair pathway by activating the enzyme PARP1. Metal stress in plants also influences these enzyme activities. HighlightsO_LIOsSRT1 can transfer a single moiety of ADP-ribose on itself as well as other nuclear proteins like histones H3 and H2A. C_LIO_LINAM, ADP-ribose and certain metal ions negatively regulate this ADP-ribose transfer. C_LIO_LIADPr of OsPARP1 and OsPARP2 links OsSRT1 to DNA damage repair pathways. C_LIO_LIOsSRT1 positively regulates the activity of OsPARP1 by ADP ribosylating it. C_LIO_LIOn plants exposure to H2O2 (oxidative stress) and Arsenic toxicity, there is a link between the increased activity of the players of DNA damage repair system and overexpression of OsSRT1. C_LI

{gamma}-Glutamyl cyclotransferases (GGCTs) belongs to class of cytosolic enzymes that are responsible for glutathione (GSH) degradation under stress conditions. They regulate GSH homeostasis through the {gamma}-glutamyl cycle which is responsible for maintaining the synthesis of GSH as well as its breakdown, enabling recycling of its constituent amino acids. Although GGCTs have been implicated in enhancing heavy metal (HMs) tolerance in plants, their role in biotic stress remains largely unexplored. Previously, OsGGCT1 was identified as a gene strongly upregulated in Fusarium stress. In this study, the GGCT1 homolog from Oryza sativa japonica was characterized for its role in conferring tolerance to Fusarium oxysporum (F.O.). Similar to abiotic factors, biotic stresses significantly impact crop yield and productivity. The rhizosphere harbors diverse microbial communities, including harmful pathogens such as F. oxysporum. Fusarium causes wilt disease in a variety of plant species, such as: tomato, legumes, rice, and Arabidopsis thaliana. Our results demonstrate that overexpression of OsGGCT1 enhanced tolerance to F. oxysporum in A. thaliana, primarily by reducing fungal spore accumulation. Transgenic plants showed elevated expression of OsGGCT1 along with AtGSH1 and AtGSH2, reduced levels of reactive oxygen species (ROS), improved growth and photosynthetic performance and enhanced activities of the antioxidant enzymes. OsGGCT1 serves as a key component in maintaining GSH homeostasis by supporting glutamate (Glu) regeneration necessary for sustained GSH biosynthesis. Overall, these findings identify OsGGCT1 as an important constituent of the GSH-mediated detoxification pathway against Fusarium oxysporum and provide valuable molecular insights for developing Fusarium-tolerant rice varieties with reduced fungal accumulation.

Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are essential regulators of plant growth, development, and stress adaptation. In this study, we performed a comprehensive genome-wide identification of SNARE genes in cucumber (Cucumis sativus L.), uncovering 51 putative members designated as CsSNAREs. Phylogenetic analysis confirmed that these genes cluster into five major clades: Qa-CsSNARE (14), Qb-CsSNARE (9), Qc-CsSNARE (10), Qb+c-CsSNARE (3), and R-CsSNARE (15). Bioinformatic analysis of their promoter regions, coupled with expression profiling under diverse abiotic stress conditions, highlighted a heightened responsiveness within the Qa-CsSNARE subfamily. To validate this, we selected representative Qa-CsSNARE genes for quantitative real-time PCR analysis under drought and salt stress. Among these, CsSYP121 was notably induced by salt treatment. We subsequently generated transgenic cucumber lines overexpressing CsSYP121 and challenged them with salinity. Phenotypic assessment, combined with measurements of reactive oxygen species (ROS) accumulation and K+/Na+ ratios, demonstrated that CsSYP121 overexpression (OE) confers enhanced salt tolerance and boosts antioxidant capacity. We propose a model wherein CsSYP121 mitigates ROS-induced cellular damage under salt stress, potentially through promoting K+/Na+ homeostasis, thereby improving plant performance under saline conditions. Our findings identify CsSYP121 as a promising candidate gene for breeding salt-tolerant crops.

Mitogen-activated protein kinases (MAPKs) are important signaling players involved in various responses to diverse environmental stresses. MAP kinase phosphatases (MKPs) are crucial negative regulators of MAPKs and control the intensity and duration of MAPK activation. It has been shown that transgenic tobacco plants with increased glutathione content display an oxidative shift and have constitutively active immunity-related MAPKs. The mechanism by which glutathione can activate or keep these MAPKs in activated state is unclear. In this study, it is shown that the Arabidopsis stress-related MAPKs, AtMPK3 and AtMPK6 are hypersensitive to a pathogen-associated molecular pattern flg22 in the cat2-1 line, under the conditions causing an altered glutathione homeostasis and elevated oxidative stress responses in this background. As AtMKP2 is the only dual specificity phosphatase deactivating AtMPK3 and AtMPK6 in response to oxidative stress, the stability of the wild-type AtMKP2 protein and the mutant version of the protein with the substitution of the cys109 in the active site with serine has been studied in wild type (Col-0) and cat2-1 background. The results indicate that AtMKP2 is a stable protein in both genetic backgrounds, whereas the active site cys109 stabilizes the protein under severe oxidative stress conditions and can be glutathionylated in vitro.

The ribosomal protein SA plays an essential role in multiple aspects and is involved in plant growth and response to various stresses. Drought threatens pepper yield and quality. However, the resistance mechanism of pepper in response to drought are complex and not yet fully understood. Here, we describe the role of CaSLP in mediating pepper tolerance to drought stress. we found that CaSLP was highly expressed under drought and salicylic acid (SA) stress, and CaSLP was localized in cell nucleus and cytomembrane. Knockout of CaSLP gene significantly decreased the pepper drought tolerance, while transient expression of CaSLP leads to drought tolerance in pepper, and overexpression of the CaSLP dramatically increased the drought stress tolerance in Arabidopsis. Furthermore, exogenous spring salicylic acid enhanced drought tolerance. The characterization of resistance molecular mechanisms in the Pseudomonas syringae pv. Tomato DC3000 (Pst.DC3000) is of great significance for the pepper yield and quality, we found that CaSLP-knockdown pepper plants demonstrated decreased Pst.DC3000 tolerance, whereas ectopic expression of the CaSLP increased the Pst.DC3000 stress tolerance in Arabidopsis. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) results showed that CaNAC035 physically interacts with CaSLP in the cell nucleus, and the CaNAC035 was identified as an upstream partner of the CaPR1 promoter and activated the transcription. Taken together, our data demonstrated that CaSLP plays an essential role in the regulation of drought stress. Our study elucidates the roles of CaSLP response to drought stress tolerance. Furthermore, a possible regulatory model and molecular mechanisms under drought stress is proposed.

This study provides a thorough exploration of the mechanisms regulating the onset of flowering in peach trees, a process principally governed by bud-dormancy. We applied untargeted metabolomics combined with a comprehensive series of molecular and biochemical experiments to scrutinize the variations in bloom times among different peach cultivars. The impact of exogenous chemical stimuli, specifically ethephon (ET) and abscisic acid (ABA), on bloom times was also evaluated. Our study revealed that the ET-induced delay in bloom time was associated with higher levels of proanthocyanidin (PA) compared to anthocyanins (ACNs) during endodormancy. Furthermore, fluctuations in the PA/ACNs ratio during dormancy demonstrated a strong correlation with the chill requirements and bloom dates of 12 distinct peach genotypes. The research further uncovers the crucial role of ABA in regulating the biosynthesis of PAs and ACNs during peach tree dormancy. Intriguingly, the exogenous application of ABA during endodormancy resulted in a reduction of PA content, leading to an earlier bloom time. We also observed variations in DAM gene expression between early- and late-blooming cultivars. The late-blooming cultivars exhibited higher transcript levels of DAM genes, elevated PA levels, and lower ABA levels compared to their early-blooming counterparts. Importantly, our study proposes PAs and ACNs as quantitative marker metabolites for endo- and ecodormancy phases. This innovative finding paves the way for developing more accurate chill and heat requirement models, thereby enabling a more precise understanding and projection of the impacts of global climate change on the phenology of tree fruit species.