State Key Laboratory of Hybrid Rice, Rice Research Institute, Sichuan Agricultural University, Chengdu 611130, China.
State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Sichuan Agricultural University, Chengdu 611130, China.
Int J Mol Sci. 2024 Jul 2;25(13):7301. doi: 10.3390/ijms25137301.
Nucleotide-binding and leucine-rich repeat receptors (NLRs) are the most important and largest class of immune receptors in plants. The gene encodes a canonical CC-NBS-LRR protein that confers resistance to rice blast fungal infections. Here, we show that the CC domain of Pi36 plays a role in cell death induction. Furthermore, self-association is required for the CC domain-mediated cell death, and the self-association ability is correlated with the cell death level. In addition, the NB-ARC domain may suppress the activity of the CC domain through intramolecular interaction. The mutations D440G next to the RNBS-D motif and D503V in the MHD motif autoactivated Pi36, but the mutation K212 in the P-loop motif inhibited this autoactivation, indicating that nucleotide binding of the NB-ARC domain is essential for Pi36 activation. We also found that the LRR domain is required for D503V- and D440G-mediated Pi36 autoactivation. Interestingly, several mutations in the CC domain compromised the CC domain-mediated cell death without affecting the D440G- or D503V-mediated Pi36 autoactivation. The autoactivate Pi36 variants exhibited stronger self-associations than the inactive variants. Taken together, we speculated that the CC domain of Pi36 executes cell death activities, whereas the NB-ARC domain suppressed CC-mediated cell death via intermolecular interaction. The NB-ARC domain releases its suppression of the CC domain and strengthens the self-association of Pi36 to support the CC domain, possibly through nucleotide exchange.
核苷酸结合和富含亮氨酸重复受体（NLRs）是植物中最重要和最大的一类免疫受体。该基因编码一种典型的 CC-NBS-LRR 蛋白，赋予水稻对稻瘟病真菌感染的抗性。在这里，我们表明 Pi36 的 CC 结构域在细胞死亡诱导中起作用。此外，CC 结构域介导的细胞死亡需要自身缔合，并且自缔合能力与细胞死亡水平相关。此外，NB-ARC 结构域可能通过分子内相互作用抑制 CC 结构域的活性。靠近 RNBS-D 基序的 D440G 突变和 MHD 基序中的 D503V 突变自动激活 Pi36，但 P 环基序中的 K212 突变抑制了这种自动激活，表明 NB-ARC 结构域的核苷酸结合对于 Pi36 的激活是必需的。我们还发现 LRR 结构域是 D503V 和 D440G 介导的 Pi36 自动激活所必需的。有趣的是，CC 结构域中的几个突变会损害 CC 结构域介导的细胞死亡，而不影响 D440G 或 D503V 介导的 Pi36 自动激活。自动激活的 Pi36 变体比非活性变体表现出更强的自身缔合。总之，我们推测 Pi36 的 CC 结构域执行细胞死亡活性，而 NB-ARC 结构域通过分子间相互作用抑制 CC 介导的细胞死亡。NB-ARC 结构域释放其对 CC 结构域的抑制，并通过核苷酸交换加强 Pi36 的自我缔合以支持 CC 结构域。
