China National Center for Rice Improvement/State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, China.
China National Center for Rice Improvement/State Key Laboratory of Rice Biology and Breeding, China National Rice Research Institute, Hangzhou 310006, China; National Nanfan Research Institute (Sanya), Chinese Academy of Agricultural Sciences, Sanya 572024, China.
Plant Commun. 2024 Oct 14;5(10):101001. doi: 10.1016/j.xplc.2024.101001. Epub 2024 Jun 10.
Nucleotide-binding site and leucine-rich repeat (NLR) proteins are activated by detecting pathogen effectors, which in turn trigger host defenses and cell death. Although many NLRs have been identified, the mechanisms responsible for NLR-triggered defense responses are still poorly understood. In this study, through a genome-wide association study approach, we identified a novel NLR gene, Blast Resistance Gene 8 (BRG8), which confers resistance to rice blast and bacterial blight diseases. BRG8 overexpression and complementation lines exhibit enhanced resistance to both pathogens. Subcellular localization assays showed that BRG8 is localized in both the cytoplasm and the nucleus. Additional evidence revealed that nuclear-localized BRG8 can enhance rice immunity without a hypersensitive response (HR)-like phenotype. We also demonstrated that the coiled-coil domain of BRG8 not only physically interacts with itself but also interacts with the KNOX Ⅱ protein HOMEOBOX ORYZA SATIVA59 (HOS59). Knockout mutants of HOS59 in the BRG8 background show enhanced resistance to Magnaporthe oryzae strain CH171 and Xoo strain CR4, similar to that of the BRG8 background. By contrast, overexpression of HOS59 in the BRG8 background will compromise the HR-like phenotype and resistance response. Further analysis revealed that HOS59 promotes the degradation of BRG8 via the 26S proteasome pathway. Collectively, our study highlights HOS59 as an NLR immune regulator that fine-tunes BRG8-mediated immune responses against pathogens, providing new insights into NLR associations and functions in plant immunity.
核苷酸结合位点和富含亮氨酸重复（NLR）蛋白通过检测病原体效应子而被激活，进而触发宿主防御和细胞死亡。尽管已经鉴定出许多 NLR，但负责 NLR 触发的防御反应的机制仍知之甚少。在这项研究中，我们通过全基因组关联研究方法鉴定了一个新的 NLR 基因，即稻瘟病抗性基因 8（BRG8），该基因赋予水稻对稻瘟病和细菌性条斑病的抗性。BRG8 的过表达和互补系表现出对两种病原体的增强抗性。亚细胞定位实验表明 BRG8 定位于细胞质和细胞核中。进一步的证据表明，核定位的 BRG8 可以增强水稻的免疫而不引起类似过敏反应（HR）的表型。我们还证明了 BRG8 的卷曲螺旋结构域不仅可以自我相互作用，还可以与 KNOX Ⅱ蛋白 HOMEOBOX ORYZA SATIVA59（HOS59）相互作用。在 BRG8 背景下敲除 HOS59 的突变体对稻瘟病菌株 CH171 和 Xoo 菌株 CR4 的抗性增强，类似于 BRG8 背景。相比之下，在 BRG8 背景下过表达 HOS59 会损害 HR 样表型和抗性反应。进一步的分析表明，HOS59 通过 26S 蛋白酶体途径促进 BRG8 的降解。总之，我们的研究强调了 HOS59 作为 NLR 免疫调节剂，精细调节 BRG8 介导的对病原体的免疫反应，为 NLR 关联和植物免疫中的功能提供了新的见解。
