Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Ciudad Politécnica de la Inovación, 46022 Valencia, Spain.
Plant Cell. 2012 Oct;24(10):4220-35. doi: 10.1105/tpc.112.103028. Epub 2012 Oct 12.
Salicylic acid (SA) signaling acts in defense and plant development. The only gene demonstrated to be required for the response to SA is Arabidopsis thaliana non-expresser of pathogenesis-related gene 1 (NPR1), and npr1 mutants are insensitive to SA. By focusing on the effect of analogs of SA on plant development, we identified mutants in additional genes acting in the SA response. In this work, we describe a gene necessary for the SA Non-Recognition-of-BTH4 (NRB4). Three nrb4 alleles recovered from the screen cause phenotypes similar to the wild type in the tested conditions, except for SA-related phenotypes. Plants with NRB4 null alleles express profound insensitivity to SA, even more than npr1. NRB4 null mutants are also sterile and their growth is compromised. Plants carrying weaker nrb4 alleles are also insensitive to SA, with some quantitative differences in some phenotypes, like systemic acquired resistance or pathogen growth restriction. When weak alleles are used, NPR1 and NRB4 mutations produce an additive phenotype, but we did not find evidence of a genetic interaction in F1 nor biochemical interaction in yeast or in planta. NRB4 is predicted to be a subunit of Mediator, the ortholog of MED15 in Arabidopsis. Mechanistically, NRB4 functions downstream of NPR1 to regulate the SA response.
水杨酸（SA）信号转导在植物防御和发育中发挥作用。唯一被证明是植物对 SA 响应所必需的基因是拟南芥非表达病原体相关基因 1（NPR1），npr1 突变体对 SA 不敏感。通过关注 SA 类似物对植物发育的影响，我们鉴定到了在 SA 反应中起作用的其他基因的突变体。在这项工作中，我们描述了一个对 SA 非识别 BTH4（NRB4）必需的基因。从筛选中恢复的三个 nrb4 等位基因在测试条件下引起的表型与野生型相似，除了与 SA 相关的表型。NRB4 缺失等位基因的植物对 SA 表现出明显的不敏感性，甚至比 npr1 更不敏感。NRB4 缺失突变体也是不育的，其生长受到影响。携带较弱 nrb4 等位基因的植物也对 SA 不敏感，在一些表型（如系统获得性抗性或病原体生长限制）上存在一些定量差异。当使用较弱的等位基因时，NPR1 和 NRB4 突变产生叠加表型，但我们在 F1 中没有发现遗传相互作用的证据，也没有在酵母或体内发现生化相互作用的证据。NRB4 预测是 Mediator 的一个亚基，在拟南芥中与 MED15 同源。从机制上讲，NRB4 作为 NPR1 的下游因子，调节 SA 反应。
