Xiao Gui, Wang Wenjuan, Liu Muxing, Li Ya, Liu Jianbin, Franceschetti Marina, Yi Zhaofeng, Zhu Xiaoyuan, Zhang Zhengguang, Lu Guodong, Banfield Mark J, Wu Jun, Zhou Bo
State Key Laboratory of Hybrid Rice, Hunan Hybrid Rice Research Center, Changsha, 410128, China.
International Rice Research Institute, Metro Manila, 1301, Philippines.
J Integr Plant Biol. 2023 Mar;65(3):810-824. doi: 10.1111/jipb.13375. Epub 2022 Dec 31.
Arms race co-evolution of plant-pathogen interactions evolved sophisticated recognition mechanisms between host immune receptors and pathogen effectors. Different allelic haplotypes of an immune receptor in the host mount distinct recognition against sequence or non-sequence related effectors in pathogens. We report the molecular characterization of the Piks allele of the rice immune receptor Pik against rice blast pathogen, which requires two head-to-head arrayed nucleotide-binding sites and leucine-rich repeat proteins. Like other Pik alleles, both Piks-1 and Piks-2 are necessary and sufficient for mediating resistance. However, unlike other Pik alleles, Piks does not recognize any known AvrPik variants of Magnaporthe oryzae. Sequence analysis of the genome of an avirulent isolate V86010 further revealed that its cognate avirulence (Avr) gene most likely has no significant sequence similarity to known AvrPik variants. Piks-1 and Pikm-1 have only two amino acid differences within the integrated heavy metal-associated (HMA) domain. Pikm-HMA interacts with AvrPik-A, -D, and -E in vitro and in vivo, whereas Piks-HMA does not bind any AvrPik variants. Characterization of two amino acid residues differing Piks-1 from Pikm-1 reveal that Piks-E229Q derived from the exchange of Glu229 to Gln229 in Piks-1 gains recognition specificity against AvrPik-D but not AvrPik-A or -E, indicating that Piks-E229Q partially restores the Pikm spectrum. By contrast, Piks-A261V derived from the exchange of Ala261 to Val261 in Piks-1 retains Piks recognition specificity. We conclude that Glu229 in Piks-1 is critical for Piks breaking the canonical Pik/AvrPik recognition pattern. Intriguingly, binding activity and ectopic cell death induction is maintained between Piks-A261V and AvrPik-D, implying that positive outcomes from ectopic assays might be insufficient to deduce its immune activity against the relevant effectors in rice and rice blast interaction.
植物 - 病原体相互作用的军备竞赛式协同进化在宿主免疫受体和病原体效应子之间演化出了复杂的识别机制。宿主中免疫受体的不同等位基因单倍型对病原体中与序列或非序列相关的效应子进行不同的识别。我们报道了水稻免疫受体Pik针对稻瘟病菌的Piks等位基因的分子特征，它需要两个头对头排列的核苷酸结合位点和富含亮氨酸重复序列的蛋白。与其他Pik等位基因一样，Piks - 1和Piks - 2对于介导抗性都是必需且充分的。然而，与其他Pik等位基因不同，Piks不识别稻瘟病菌任何已知的AvrPik变体。对无毒分离株V86010的基因组序列分析进一步表明，其同源无毒（Avr）基因很可能与已知的AvrPik变体没有显著的序列相似性。Piks - 1和Pikm - 1在整合的重金属相关（HMA）结构域内只有两个氨基酸差异。Pikm - HMA在体外和体内都与AvrPik - A、-D和-E相互作用，而Piks - HMA不结合任何AvrPik变体。对Piks - 1与Pikm - 1不同的两个氨基酸残基的表征表明，Piks中由Piks - 1的Glu229替换为Gln229得到的Piks - E229Q获得了针对AvrPik - D的识别特异性，但不针对AvrPik - A或-E，这表明Piks - E229Q部分恢复了Pikm的识别谱。相比之下，Piks中由Piks - 1的Ala261替换为Val261得到的Piks - A261V保留了Piks的识别特异性。我们得出结论，Piks - 1中的Glu229对于Piks打破典型的Pik/AvrPik识别模式至关重要。有趣的是，Piks - A261V和AvrPik - D之间保持着结合活性和异位细胞死亡诱导，这意味着异位试验的阳性结果可能不足以推断其在水稻与稻瘟病菌相互作用中对相关效应子的免疫活性。
