富含核苷酸结合亮氨酸的重复序列(NB-LRR,或NLR)受体介导病原体识别。拟南芥NLRRPP1通过与C末端LRR直接缔合,识别卵菌Hyaloperonosporaarabidopsidis的串联WY结构域效应子ATR1。我们从两种拟南芥生态型中分离并表征了同源NLR基因RPP1-EstA和RPP1-ZdrA,Estland(Est-1)和Zdarec(Zdr-1),负责识别ATR1等位基因的新光谱。RPP1-EstA和-ZdrA编码几乎相同的NLR,这些NLR在系统发育上不同于已知的免疫激活RPP1同源物,并具有极大扩展的LRR结构域。ATR1的定点诱变和截短分析表明,这些同源物识别ATR1的2(nd)WY结构域的新表面,部分由LRR结构域的C末端区域指定。与杂种不相容性相关的RPP1基因座的合成比较表明,这些功能是独立进化的。密切相关的RPP1同源物通过LRR扩展和序列变异使其识别光谱多样化,允许他们检测同一病原体效应物的多个表面。改造NLR受体特异性可能需要重复扩增和定制的氨基酸变异的类似组合。
Nucleotide-binding leucine-rich repeat (NB-LRR, or NLR) receptors mediate pathogen recognition. The Arabidopsis thaliana NLR
RPP1 recognizes the tandem WY-domain effector ATR1 from the oomycete Hyaloperonospora arabidopsidis through direct association with C-terminal LRRs. We isolated and characterized homologous NLR genes
RPP1-EstA and
RPP1-ZdrA from two Arabidopsis ecotypes, Estland (Est-1) and Zdarec (Zdr-1), responsible for recognizing a novel spectrum of ATR1 alleles. RPP1-EstA and -ZdrA encode nearly identical NLRs that are phylogenetically distinct from known immunity-activating
RPP1 homologs and possess greatly expanded LRR domains. Site-directed mutagenesis and truncation analysis of ATR1 suggests that these homologs recognize a novel surface of the 2(nd) WY domain of ATR1, partially specified by a C-terminal region of the LRR domain. Synteny comparison with
RPP1 loci involved in hybrid incompatibility suggests that these functions evolved independently. Closely related
RPP1 homologs have diversified their recognition spectra through LRR expansion and sequence variation, allowing them to detect multiple surfaces of the same pathogen effector. Engineering NLR receptor specificity may require a similar combination of repeat expansion and tailored amino acid variation.