• Nitric oxide (NO) regulates the deployment of a phalanx of immune responses, chief among which is the activation of a constellation of defence‐related genes. However, the underlying molecular mechanisms remain largely unknown. The Arabidopsis thaliana zinc finger transcription factor (ZF‐TF), S‐nitrosothiol (SNO) Regulated 1 (SRG1), is a central target of NO bioactivity during plant immunity. Here we characterize the remaining members of the SRG gene family.
• Both SRG2 and, especially, SRG3 were positive regulators of salicylic acid‐dependent plant immunity. Analysis of SRG single, double and triple mutants implied that SRG family members have additive functions in plant immunity and, surprisingly, are under reciprocal regulation.
• SRG2 and SRG3 localized to the nucleus and functioned as ethylene‐responsive element binding factor‐associated amphiphilic repression (EAR) domain‐dependent transcriptional repressors: NO abolished this activity for SRG3 but not for SRG2. Consistently, loss of GSNOR function, resulting in increased (S)NO concentrations, fully suppressed the disease resistance phenotype established from SRG3 but not SRG2 overexpression. Remarkably, SRG3 but not SRG2 was S‐nitrosylated in vitro and in vivo.
• Our findings suggest that the SRG family has separable functions in plant immunity, and, surprisingly, these ZF‐TFs exhibit reciprocal regulation. It is remarkable that, through neofunctionalization, the SRG family has evolved to become differentially regulated by the key immune‐related redox cue, NO.

中文翻译：

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拟南芥锌指蛋白SRG2和SRG3是植物免疫力的正调节剂，并受一氧化氮差异调节

• 一氧化氮（NO）调节免疫反应方阵的部署，其中主要是防御相关基因群的激活。然而，基本的分子机制仍然很大程度上未知。的拟南芥锌指转录因子（ZF-TF），š -nitrosothiol（SNO）监管1（SRG1），是植物免疫期间NO生物活性的中心目标。在这里，我们表征了SRG基因家族的其余成员。
• SRG2和特别是SRG3都是水杨酸依赖性植物免疫力的正调节剂。对SRG单突变体，双突变体和三突变体的分析表明，SRG家族成员在植物免疫中具有加性功能，并且令人惊讶地，它们处于相互调节之下。
• SRG2和SRG3定位于细胞核，并起着与乙烯反应元件结合因子相关的两亲阻抑（EAR）域依赖性转录阻遏物的作用：NO取消了SRG3的这种活性，但没有消除SRG2的这种活性。一致地，GSNOR功能的丧失，导致（S）NO浓度增加，完全抑制了由SRG3建立的抗病性表型，但没有完全抑制SRG2的过表达。值得注意的是，在体外和体内，SRG3而不是SRG2被S-亚硝基化。
• 我们的发现表明SRG家族在植物免疫方面具有可分离的功能，而且令人惊讶的是，这些ZF-TFs具有相互调节作用。值得注意的是，通过新功能化，SRG家族已进化为受到关键的免疫相关氧化还原线索NO的差异调节。