Abstract：
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 mechanism responsible for NLR-triggered defense responses are still poorly understood. In this study, through GWAS approach, we identified a novel NLR gene, Blast Resistance Gene 8 (BRG8), conferring resistance to rice blast and bacterial blight diseases. Consistently, the BRG8 overexpression and complementation lines exhibited enhanced resistance to both pathogens. Subcellular localization assays showed that BRG8 localized in both cytoplasm and nucleus. More evidence revealed that nuclear-localized BRG8 enhanced rice immunity without hypersensitive response (HR)-like phenotype. Furthermore, we also demonstrated the CC domain of BRG8 not only physically interacted with itself, but also interacted with the KNOX Ⅱ protein HOMEOBOX ORYZA SATIVA59 (HOS59). Knockout of HOS59 in BRG8 background showed enhanced resistance to M. oryzae strain CH171 and Xoo strain CR4, similar to BRG8 background. In contrast, overexpression of HOS59 in BRG8 background, compromised 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 NLR immune regulators, fine-tune BRG8-mediated immune responses against pathogens, and provides new insights into NLR association and function in plant immunity.
摘要：
通过检测病原体效应子激活核苷酸结合位点和富含亮氨酸的重复序列（NLR）蛋白，进而引发宿主防御和细胞死亡。尽管已经确定了许多NLR，NLR触发防御反应的机制仍然知之甚少.在这项研究中,通过GWAS方法，我们发现了一个新的NLR基因,Blast抗性基因8(BRG8),赋予稻瘟病和白叶枯病抗性。始终如一，BRG8过表达和互补系表现出对两种病原体的增强抗性。亚细胞定位分析显示BRG8定位在细胞质和细胞核中。更多证据表明，核定位的BRG8增强了水稻的免疫力，而没有超敏反应（HR）样表型。此外，我们还证明了BRG8的CC域不仅与自身物理相互作用，但也与KNOXⅡ蛋白HOMEOBOXORYZASATIVA59（HOS59）相互作用。BRG8背景中HOS59的敲除显示对米曲霉菌株CH171和Xoo菌株CR4的抗性增强,类似于BRG8背景。相比之下,HOS59在BRG8背景中的过表达，损害了HR样表型和抗性反应。进一步分析显示HOS59通过26S蛋白酶体途径促进BRG8的降解。总的来说，我们的研究强调HOS59作为NLR免疫调节剂，微调BRG8介导的针对病原体的免疫反应，并为NLR在植物免疫中的关联和功能提供了新的见解。
