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IgASE1, a C18 Δ9-specific polyunsaturated fatty acid elongase from the marine microalga Isochrysis galbana, is able to convert linoleic acid and α-linolenic acid to eicosadienoic acid and eicosatrienoic acid in Arabidopsis. Eicosadienoic acid and eicosatrienoic acid are precursors of arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, which are synthesized via the Δ8 desaturation biosynthetic pathways. This study shows that the IgASE1-expressing transgenic Arabidopsis exhibited altered morphology (decreased leaf area and biomass) and enhanced drought resistance compared to wild-type plants. The transgenic Arabidopsis were hypersensitive to abscisic acid (ABA) during seed germination, post-germination growth, and seedling development. They had elevated leaf ABA levels under well-watered and dehydrated conditions and their stomata were more sensitive to ABA. Exogenous application of eicosadienoic acid and eicosatrienoic acid can mimic ABA and drought responses in the wild type plants, similar to that found in the transgenic ones. The transcript levels of genes involved in the biosynthesis of ABA (NCED3, ABA1, AAO3) as well as other stress-related genes were upregulated in this transgenic line upon osmotic stress (300mM mannitol). Taken together, these results indicate that these two eicosapolyenoic acids or their derived metabolites can mitigate the effects of drought in transgenic Arabidopsis, at least in part, through the action of ABA. [ABSTRACT FROM AUTHOR]

CsCHYR1 (CHY ZINC-FINGER AND RING PROTEIN1) encodes a RING (Really Interesting New Gene) finger E3 ubiquitin ligase involved in ubiquitin-mediated protein degradation and plays an important role for cucumber to resist drought stress. Here, we obtain one of the candidate proteins CsCHYR1 that probably interacts with CsATAF1 by yeast-two hybrid screening. Subsequently, it is verified that CsCHYR1 interacts with CsATAF1 and has self-ubiquitination activity. When the cysteine residue at 180 in the RING domain of CsCHYR1 is replaced by serine or alanine, ubiquitin could not be transported from E2 to the substrate. CsCHYR1 ubiquitinates CsATAF1 and affects the stability of CsATAF1 when plants are subjected to drought stress. The expression level of CsCHYR1 is increased by 4-fold after ABA treatment at 9 h. The Atchyr1 mutants perform an ABA-hyposensitive phenotype and have a lower survival rate than Col-0 and CsCHYR1 Atchyr1 lines. In addition, CsCHYR1 interacts with CsSnRK2.6. Therefore, our study reveals a CsSnRK2.6-CsCHYR1-CsATAF1 complex to promote the drought stress response by decreasing CsATAF1 protein accumulation and inducing stomatal closure. Those findings provide new ideas for cucumber germplasm innovation from the perspective of biochemistry and molecular biology. • CsCHYR1 interacts with and ubiquitinates CsATAF1. • Cys180 is substituted by Ser or Ala, and the E3 activity of CsCHYR1 is abolished. • The stability of CsATAF1 is affected by drought stress. [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]