BACKGROUND Exposure of plants to different environmental insults instigates significant changes in the cellular redox tone driven in part by promoting the production of reactive nitrogen species. The key player, nitric oxide (NO) is a small gaseous diatomic molecule, well-known for its signaling role during stress. In this study, we focused on abscisic acid (ABA) metabolism-related genes that showed differential expression in response to the NO donor S-nitroso-L-cysteine (CySNO) by conducting RNA-seq-based transcriptomic analysis. RESULTS CySNO-induced ABA-related genes were identified and further characterized. Gene ontology terms for biological processes showed most of the genes were associated with protein phosphorylation. Promoter analysis suggested that several cis-regulatory elements were activated under biotic and/or abiotic stress conditions. The ABA biosynthetic gene AtAO3 was selected for validation using functional genomics. The loss of function mutant atao3 was found to differentially regulate oxidative and nitrosative stress. Further investigations for determining the role of AtAO3 in plant defense suggested a negative regulation of plant basal defense and R-gene-mediated resistance. The atao3 plants showed resistance to virulent Pseudomonas syringae pv. tomato strain DC3000 (Pst DC3000) with gradual increase in PR1 gene expression. Similarly, atao3 plants showed increased hypersensitive response (HR) when challenged with Pst DC3000 (avrB). The atgsnor1-3 and atsid2 mutants showed a susceptible phenotype with reduced PR1 transcript accumulation. Drought tolerance assay indicated that atao3 and atnced3 ABA-deficient mutants showed early wilting, followed by plant death. The study of stomatal structure showed that atao3 and atnced3 were unable to close stomata even at 7 days after drought stress. Further, they showed reduced ABA content and increased electrolyte leakage than the wild-type (WT) plants. The quantitative polymerase chain reaction analysis suggested that ABA biosynthesis genes were down-regulated, whereas expression of most of the drought-related genes were up-regulated in atao3 than in WT. CONCLUSIONS AtAO3 negatively regulates pathogen-induced salicylic acid pathway, although it is required for drought tolerance, despite the fact that ABA production is not totally dependent on AtAO3, and that drought-related genes like DREB2 and ABI2 show response to drought irrespective of ABA content.

中文翻译：

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一氧化氮诱导的AtAO3差异调节拟南芥中的植物防御和干旱耐受性。

背景技术将植物暴露于不同的环境侵害导致部分地通过促进活性氮物质的产生而驱动的细胞氧化还原色调的显着变化。一氧化氮（NO）是主要的气体分子，它是一种小气态双原子分子，以在压力下的信号传导作用而闻名。在这项研究中，我们集中在脱落酸（ABA）代谢相关的基因，通过进行基于RNA-seq的转录组分析，该基因在NO供体S-亚硝基-L-半胱氨酸（CySNO）的响应中表现出差异表达。结果鉴定并进一步鉴定了CySNO诱导的ABA相关基因。生物过程的基因本体术语表明，大多数基因与蛋白质磷酸化有关。启动子分析表明，在生物和/或非生物胁迫条件下，几种顺式调节元件被激活。使用功能基因组学选择了ABA生物合成基因AtAO3进行验证。发现功能突变体atao3的丧失差异性地调节氧化和亚硝化胁迫。确定AtAO3在植物防御中的作用的进一步研究表明，对植物基础防御和R基因介导的抗性具有负面调节作用。atao3植物显示出对强力假单胞菌丁香假单胞菌的抗性。番茄品系DC3000（Pst DC3000）的PR1基因表达逐渐增加。同样，atao3植物在受到Pst DC3000（avrB）攻击时表现出增加的超敏反应（HR）。atgsnor1-3和atsid2突变体显示出具有减少的PR1转录物积累的易感表型。耐旱性测定表明atao3和atnced3 ABA缺陷型突变体表现出早期枯萎，然后死亡。对气孔结构的研究表明，即使在干旱胁迫后的第7天，atao3和atnced3也无法关闭气孔。此外，与野生型（WT）植物相比，它们显示出降低的ABA含量和增加的电解质泄漏。定量聚合酶链反应分析表明，ABA的生物合成基因被下调，而与干旱相关的大多数干旱相关基因的表达在atao3中被上调。结论AtABA3负调控病原体诱导的水杨酸途径，尽管它是耐旱性所必需的，尽管事实上ABA的产生并不完全依赖于AtAO3，