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As a plant-specific transcription factor, lateral organ boundaries domain (LBD) protein was reported to regulate plant growth and stress response, but the functional research of subfamily II genes is limited. SlMYC2, a master regulator of Jasmonic acid response, has been found to exhibit high expression levels in fruit and has been implicated in the regulation of fruit ripening and resistance to Botrytis. However, its role in fruit expansion remains unknown. In this study, we present evidence that a subfamily II member of LBD, namely SlLBD40, collaborates with SlMYC2 in the regulation of fruit expansion. Overexpression of SlLBD40 significantly promoted fruit growth by promoting mesocarp cell expansion, while knockout of SlLBD40 showed the opposite result. Similarly, SlMYC2 knockout resulted in a significant decrease in cell expansion within the fruit. Genetic analysis indicated that SlLBD40-mediated cell expansion depends on the expression of SlMYC2. SlLBD40 bound to the promoter of SlEXPA5, an expansin gene, but did not activate its expression directly. While, the co-expression of SlMYC2 and SlLBD40 significantly stimulated the activation of SlEXPA5, leading to an increase in fruit size. SlLBD40 interacted with SlMYC2 and enhanced the stability and abundance of SlMYC2. Furthermore, SlMYC2 directly targeted and activated the expression of SlLBD40, which is essential for SlLBD40-mediated fruit expansion. In summary, our research elucidates the role of the interaction between SlLBD40 and SlMYC2 in promoting cell expansion in tomato fruits, thus providing novel insights into the molecular genetics underlying fruit growth., (© 2024 Society for Experimental Biology and John Wiley & Sons Ltd.)

The WRKY transcription factors (TFs) are involved in aluminum (Al) stress and jasmonic acid (JA)-regulated resistance responses. WRKYs act as regulators of Al-activated malate transporter (ALMT) proteins (anion channels) by directly binding to their promoters and altering malate efflux, thereby regulating Al ion toxicity in plant roots. JA enhances Al-induced root growth inhibition in Arabidopsis. However, the relationship between WRKY and ALMT genes and their involvement in JA-mediated root growth inhibition during Al stress in tomato remain unknown. Here, we demonstrate a similar phenomenon that JA enhances Al-induced root growth inhibition in tomato (Solanum lycopersicum). By analyzing RNA-seq data and tissue-specific expression data from public databases, we selected 17 WRKY and 6 ALMT family genes to identify the genes participated in this process. The promoters of many of the selected genes contained MeJA responsive element, G-box (target site of MYC2, a core TF of JA signaling), and W-box (target site for WRKY). Quantitative real-time PCR was performed to evaluate the expression levels of selected WRKY and ALMT genes under AlCl 3 and Methyl jasmonate (MeJA) treatment. SlMYC2-VIGS seedlings and jasmonic acid-insensitive1 (jai1) mutant were also employed to analyze the expression patterns of selected genes. We find that SlALMT3 is responsible for the crosstalk regulatory mechanism between Al and JA in root growth inhibition, and 6 SlWRKYs may act as the upstream regulators of SlALMT3 in this crosstalk response. This study is initial and informative in exploring the crosstalk regulatory mechanism between JA and Al in tomato., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

NACs are one of the largest transcription factor families in plants and are involved in the response to abiotic stress. BoNAC019, a homologue of AtNAC019, was isolated from cabbage (Brassica oleracea). BoNAC019 was localized in the nucleus and functioned as a transcriptional activator. The expression of BoNAC019 was induced by dehydration, salt, abscisic acid (ABA), and H 2 O 2 treatments. BoNAC019 overexpressing plants were generated to explore the function of BoNAC019 in response to drought stress. Overexpression (OE) of BoNAC019 reduced drought tolerance with lower survival rate, higher water loss rate, lower proline content and ABA content. The seed germination and root length assays of BoNAC019-OE plants showed decreased sensitivity to ABA. Under drought condition, antioxidant enzymes and anthocyanin content decreased in BoNAC019 -OE plants, resulting in the accumulation of more reactive oxygen species (ROS), which cause damage to plants. Several stress-responsive genes, antioxidant enzymatic genes, anthocyanin biosynthetic genes and ABA signaling genes were down-regulated under drought condition while the ABA catabolism genes were induced in BoNAC019-OE plants under both normal and drought conditions. Our results demonstrated that BoNAC019 might participated in regulating drought tolerance by inducing ABA catabolism genes and decreasing ABA content.

Initiation and progression of leaf senescence are triggered by various environmental stressors and phytohormones. Jasmonic acid (JA) and darkness accelerate leaf senescence in plants. However, the mechanisms that integrate these two factors to initiate and regulate leaf senescence have not been identified. Here, we report a transcriptional regulatory module centred on a novel tomato WRKY transcription factor, SlWRKY37, responsible for both JA- and dark-induced leaf senescence. The expression of SlWRKY37 , together with SlMYC2 , encoding a master transcription factor in JA signalling, was significantly induced by both methyl jasmonate (MeJA) and dark treatments. SlMYC2 binds directly to the promoter of SlWRKY37 to activate its expression. Knock out of SlWRKY37 inhibited JA- and dark-induced leaf senescence. Transcriptome analysis and biochemical experiments revealed SlWRKY53 and SlSGR1 (S. lycopersicum senescence-inducible chloroplast stay-green protein 1) as direct transcriptional targets of SlWRKY37 to control leaf senescence. Moreover, SlWRKY37 interacted with a VQ motif-containing protein SlVQ7, and the interaction improved the stability of SlWRKY37 and the transcriptional activation of downstream target genes. Our results reveal the physiological and molecular functions of SlWRKY37 in leaf senescence, and offer a target gene to retard leaf yellowing by reducing sensitivity to external senescence signals, such as JA and darkness. [ABSTRACT FROM AUTHOR]

Seed germination is a critical phase for the life cycle and propagation of higher plants. This study explores the role of SlWRKY37, a WRKY transcription factor in tomato, in modulating seed germination. We discovered that SlWRKY37 expression is markedly downregulated during tomato seed germination. Through CRISPR/Cas9-mediated editing, we demonstrate that SlWRKY37 knockout enhances germination, while its overexpression results in a delay compared to the wild type. Transcriptome analysis revealed 679 up-regulated and 627 down-regulated genes in Slwrky37 -CRISPR deletion mutants relative to the wild type. Gene ontology (GO) enrichment analysis indicated these differentially expressed genes are linked to seed dormancy, abscisic acid homeostasis, and protein phosphorylation pathways. Bioinformatics and biochemical assays identified SlABI5-like7 and SlLEA2 as key transcriptional targets of SlWRKY37, integral to tomato seed dormancy regulation. Additionally, SlWRKY37 was found to be post-translationally phosphorylated at Ser65, a modification crucial for its transcriptional activation. Our findings elucidate the regulatory role of SlWRKY37 in seed dormancy, suggesting its potential as a target for gene editing to reduce seed dormancy in tomato breeding programs. • SlWRKY37 functions as a negative regulator in tomato seed germination. • As An upstream regulator, SlWRKY37 activates SlABI5-like7 and SlLEA2 expression. • SlWRKY37's phosphorylation is essential for its transcriptional activity. [ABSTRACT FROM AUTHOR]

SUMMARY: Cucumber (Cucumis sativus) originated in tropical areas and is very sensitive to low temperatures. Cold acclimation is a universal strategy that improves plant resistance to cold stress. In this study, we report that heat shock induces cold acclimation in cucumber seedlings, via a process involving the heat‐shock transcription factor HSFA1d. CsHSFA1d expression was improved by both heat shock and cold treatment. Moreover, CsHSFA1d transcripts accumulated more under cold treatment after a heat‐shock pre‐treatment than with either heat shock or cold treatment alone. After exposure to cold, cucumber lines overexpressing CsHSFA1d displayed stronger tolerance for cold stress than the wild type, whereas CsHSFA1d knockdown lines obtained by RNA interference were more sensitive to cold stress. Furthermore, both the overexpression of CsHSFA1d and heat‐shock pre‐treatment increased the endogenous jasmonic acid (JA) content in cucumber seedlings after cold treatment. Exogenous application of JA rescued the cold‐sensitive phenotype of CsHSFA1d knockdown lines, underscoring that JA biosynthesis is key for CsHSFA1d‐mediated cold tolerance. Higher JA content is likely to lead to the degradation of CsJAZ5, a repressor protein of the JA pathway. We also established that CsJAZ5 interacts with CsICE1. JA‐induced degradation of CsJAZ5 would be expected to release CsICE1, which would then activate the ICE–CBF–COR pathway. After cold treatment, the relative expression levels of ICE–CBF–COR signaling pathway genes, such as CsICE1, CsCBF1, CsCBF2 and CsCOR1, in CsHSFA1d overexpression lines were significantly higher than in the wild type and knockdown lines. Taken together, our results help to reveal the mechanism underlying heat shock‐induced cold acclimation in cucumber. Significance Statement: Cold acclimation is a universal strategy that improves plant resistance to cold stress. In this study, we discovered that a heat‐shock pre‐treatment improves the tolerance of cucumber seedlings for low‐temperature stress, and that CsHSFA1d and JA play important roles in this cold acclimation process. Our results will help to reveal the mechanism underlying heat shock‐induced cold acclimation in cucumber. [ABSTRACT FROM AUTHOR]

Background: TLPs (Tubby-like proteins) are widespread in eukaryotes and highly conserved in plants and animals. TLP is involved in many biological processes, such as growth, development, biotic and abiotic stress responses, while the underlying molecular mechanism remains largely unknown. In this paper we characterized the biological function of cucumber (Cucumis sativus L.) Tubby-like protein 8 (CsTLP8) in Arabidopsis. Results: In cucumber, the expression of the tubby-like protein CsTLP8 was induced by NaCl treatment, but reduced by PEG (Polyethylene Glycol) and ABA (Abscisic Acid) treatment. Subcellular localization and transcriptional activation activity analysis revealed that CsTLP8 possessed two characteristics of classical transcription factors: nuclear localization and trans-activation activity. Yeast two-hybrid assay revealed interactions of CsTLP8 with CsSKP1a and CsSKP1c, suggesting that CsTLP8 might function as a subunit of E3 ubiquitin ligase. The growth activity of yeast with ectopically expressed CsTLP8 was lower than the control under NaCl and mannitol treatments. Under osmotic and salt stresses, overexpression of CsTLP8 inhibited seed germination and the growth of Arabidopsis seedlings, increased the content of MDA (Malondialdehyde), and decreased the activities of SOD (Superoxide Dismutase), POD (Peroxidase) and CAT (Catalase) in Arabidopsis seedlings. Overexpression of CsTLP8 also increased the sensitivity to ABA during seed germination and ABA-mediated stomatal closure. Conclusion: Under osmotic stress, CsTLP8 might inhibit seed germination and seedling growth by affecting antioxidant enzymes activities. CsTLP8 acts as a negative regulator in osmotic stress and its effects may be related to ABA. [ABSTRACT FROM AUTHOR]

Highlights • PvNAC1 cDNA was isolated from switchgrass (Panicum virgatum L.) and its protein was located in the nucleus with the C-terminal region containing a transcriptional activation domain. • Overexpression of PvNAC1 increased biomass yield and cellulose content whereas suppressing expression of PvNAC1 by RNAi reduced the biomass dry weight. • Overexpression of PvNAC1 showed more tolerance to salt stress by reducing Na + content in shoot and root, and enhancing ROS scavenging enzyme activities, while RNAi plants were more sensitive to salt stress. • These results show that PvNAC1 functions as a transcriptional activator in response to salt stress and growth. Abstract Switchgrass (Panicum virgatum L.) is a bioenergy crop; thus, it is important to improve biomass to effectively produce bioethanol, particularly under adverse stress conditions. NAC transcription factors are involved in the abiotic stress response. PvNAC1 was isolated in the nucleus of switchgrass, with its C-terminal region containing a transcriptional activation domain. PvNAC1 expression was induced by dehydration, salt, H 2 O 2 , and abscisic acid treatments. Overexpressing (OE) PvNAC1 improved growth performance, leading to significantly taller and heavier (dry weight) plants. Moreover, cellulose content was significantly higher in OE plants, indicating that PvNAC1 plays an important role regulating growth and bioethanol production. PvNAC1 RNA interference (RNAi) switchgrass plants exhibited reduced dry weight and cellulose content. OE PvNAC1 enhanced tolerance to salt stress, through higher reactive oxygen species scavenging ability and less Na+ and more K+ accumulation in roots and shoots. RNAi plants were more sensitive to salt stress. The quantitative polymerase chain reaction results revealed that some stress responsive genes, three antioxidant enzymatic genes, and an ion homeostasis-related gene were upregulated in OE plants and downregulated in RNAi plants. These results show that PvNAC1 functions as a transcriptional activator in response to salt stress and growth. [ABSTRACT FROM AUTHOR]

The NAC transcription factors play vital roles in responding to drought stress in plants; however, the molecular mechanisms remain largely unknown in cucumber. Suppression of CsATAF1 via RNA interference (RNAi) weakened drought stress tolerance in cucumber due to a higher water loss rate in leaves, a higher level of hydrogen peroxide (H2O2) and superoxide radicals (O2 ⋅-), increased malondialdehyde (MDA) content, lower Fv/Fm ratios and lower antioxidant enzyme activity. The analysis of root length and stomatal apertures showed that CsATAF1-RNAi cucumber plants were less responsive to ABA. In contrast, CsATAF1-overexpression (OE) plants showed increased drought stress tolerance and sensitivity to ABA. Quantitative PCR (qPCR) analysis showed that expression of several stress-responsive genes was significantly up-regulated in CsATAF1-OE transformants and down-regulated in CsATAF1-RNAi transformants. CsABI5, CsCu-ZnSOD and CsDREB2C were verified as direct target genes of CsATAF1. Yeast one-hybrid analysis and electrophoretic mobility shift assay (EMSA) further substantiated that CsATAF1 bound to the promoters of CsABI5, CsCu-ZnSOD and CsDREB2C. Transient expression in tobacco leaves and cucumber protoplasts showed that CsATAF1 directly up-regulated the expression of CsABI5, CsCu-ZnSOD and CsDREB2C. Our results demonstrated that CsATAF1 functioned as a positive regulator in response to drought stress by an ABA-dependent pathway and decreasing reactive oxygen species (ROS) accumulation in cucumber. [ABSTRACT FROM AUTHOR]

Cucumber (Cucumis sativus L.) is a high water-demanding and drought-susceptible vegetable crop. Basic leucine zipper (bZIP) transcription factors (TFs) have been linked to drought stress response in plants. Here we characterized a G subfamily gene in cucumber, CsbZIP50 , which was strongly induced by drought stress and an exogenous abscisic acid (ABA) treatment. Under drought stress, CsbZIP50 -overexpressing plants exhibited enhanced drought tolerance compared with wild-type plants, as indicated by the higher antioxidant enzyme activities but lower reactive oxygen species (ROS) and malondialdehyde contents. In addition, overexpression of CsbZIP50 enhanced cucumber's sensitivity to exogenously applied ABA, and up-regulated the expression of its stress-related genes. Moreover, we found that CsbZIP50 activated CsRD29 expression by directly binding to the G-box/ABRE cis-acting element in its promoter, both in vitro and in vivo. Yeast two-hybrid, luciferase complementation imaging, and pull-down assays showed that CsbZIP50 physically interacted with two IQ domain-containing proteins, CsIQD1 and CsIQD4, both of which promoted the ability of CsbZIP50 to activate the expression of CsRD29. Taken together, our results show that CsbZIP50 enhances drought stress tolerance in cucumber by regulating drought-responsive gene expression and ROS levels. • CsbZIP50 is a G subfamily of the bZIP TF, which was induced by drought stress and exogenous ABA treatment. • Expression of CsbZIP50 positively regulates drought tolerance by improving stomata closure and ROS scavenging. • CsbZIP50 targeted CsRD29A and the expression activation effect was enhanced by interacting with CsIQD1 and CsIQD4. [ABSTRACT FROM AUTHOR]

• SlLBD40 belongs to subfamily II of the LBD family of genes in tomato and was highly expressed in roots and fruit. • SlLBD40 showed an early response to PEG and NaCl treatment. • SlLBD40 expression was dependent on JA signaling and it might be downstream of SlMYC2. • Compared with overexpressing transgenic and WT tomato plants, knockout of SlLBD40 by CRISPR/Cas9 enhanced the drought tolerance of tomato. The LATERAL ORGAN BOUNDARIES DOMAIN (LBD)-containing genes are plant-specific genes that play important roles in lateral organ development. In this study, we identified LBD40 (Solyc02g085910), which belongs to subfamily II of the LBD family of genes in tomato. LBD40 was highly expressed in roots and fruit. LBD40 expression was significantly induced by PEG and salt. Moreover, SlLBD40 expression was induced by methyl jasmonate treatment, while SlLBD40 expression could not be induced in the jasmonic acid-insensitive1 (jai1) mutant or MYC2 -silenced plants, in which jasmonic acid (JA) signaling was disrupted. These findings demonstrate that SlLBD40 expression was dependent on JA signaling and that it might be downstream of SlMYC2 , which is the master transcription factor in the JA signal transduction pathway. Overexpressing and CRISPR/Cas9 mediated knockout transgenic tomato plants were generated to explore SlLBD40 function. The drought tolerance test showed that two SlLBD40 knockout lines wilted slightly, while SlLBD40 overexpressing plants suffered severe wilting. The statistical water loss rate and midday leaf water potential also confirmed that knockout of SlLBD40 improved the water-holding ability of tomato under drought conditions. Taken together, our study demonstrates that SlLBD40 , involved in JA signaling, was a negative regulator of drought tolerance and that knockout of SlLBD40 enhanced drought tolerance in tomato. This study also provides a novel function of SlLBD40 , which belongs to subfamily II of LBD genes. [ABSTRACT FROM AUTHOR]