Plant disease resistance (R) gene-mediated effector-triggered immunity (ETI) is usually associated with hypersensitive response (HR) and provides robust and race-specific disease resistance against pathogenic infection. The activation of ETI and HR in plants is strictly regulated, and improper activation will lead to cell death. Xa27 is an executor-type R gene in rice induced by the TAL effector AvrXa27 and confers disease resistance to Xanthomonas oryzae pv. oryzae (Xoo). Here we reported the characterization of a transgenic line with lesion mimic phenotype, designated as Spotted leaf and resistance 1 (Slr1), which was derived from rice transformation with a genomic subclone located 5,125 bp downstream of the Xa27 gene. Slr1 develops spontaneous lesions on its leaves caused by cell death and confers disease resistance to both Xoo and Xanthomonas oryzae pv. oryzicola. Further investigation revealed that the Slr1 phenotype resulted from the ectopic expression of an Xa27 paralog gene, designated as Xa27B, in the inserted DNA fragment at the Slr1 locus driven by a truncated CaMV35Sx2 promoter in reverse orientation. Disease evaluation of IRBB27, IR24, and Xa27B mutants with Xoo strains expressing dTALE-Xa27B confirmed that Xa27B is a functional executor-type R gene. The functional XA27B-GFP protein was localized to the endoplasmic reticulum and apoplast. The identification of Xa27B as a new functional executor-type R gene provides additional genetic resources for studying the mechanism of executor-type R protein-mediated ETI and developing enhanced and broad-spectrum disease resistance to Xoo through promoter engineering.

Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

植物抗病性（R）基因介导的效应子触发免疫（ETI）通常与过敏反应（HR）相关，并提供针对病原体感染的强大且种族特异性的抗病性。植物中ETI和HR的激活受到严格调控，激活不当会导致细胞死亡。Xa27是水稻中由 TAL 效应子 AvrXa27 诱导的执行型R基因，赋予对米黄单胞菌(Xanthomonas oryzae pv. ) 的抗病性。米曲霉（Xoo）。在这里，我们报道了具有模拟病变表型的转基因品系的特征，命名为斑点叶和抗性1（Slr1），该品系源自水稻转化，基因组亚克隆位于Xa27基因下游5,125 bp处。Slr1因细胞死亡而在其叶子上产生自发病变，并赋予对Xoo和米黄单胞菌pv 的抗病性。稻科拉。进一步研究表明，Slr1表型是由Xa27旁系同源基因（称为Xa27B）异位表达所致，该基因位于Slr1基因座的插入 DNA 片段中，由截短的 CaMV35Sx2 启动子反向驱动。使用表达 dTALE-Xa27B 的Xoo菌株对IRBB27、IR24 和Xa27B突变体进行疾病评估，证实Xa27B是功能性执行型R基因。功能性 XA27B-GFP 蛋白定位于内质网和质外体。Xa27B作为一种新的功能性执行子型R基因的鉴定，为研究执行子型R蛋白介导的ETI机制以及通过启动子工程开发对Xoo增强的广谱抗病性提供了额外的遗传资源。

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