Plants recognize surrounding microbes by sensing microbe-associated molecular patterns (MAMPs) to activate pattern-triggered immunity (PTI). Despite their significance for microbial control, the evolution of PTI responses remains largely uncharacterized. Employing comparative transcriptomics of six Arabidopsis thaliana accessions and three additional Brassicaceae species for PTI responses to the MAMP flg22, we identified a set of genes with expression changes under purifying selection in the Brassicaceae species and genes exhibiting species-specific expression signatures. Variation in flg22-triggered transcriptome and metabolome responses across Brassicaceae species was incongruent with their phylogeny while expression changes were strongly conserved within A. thaliana, suggesting directional selection for some species-specific gene expression. We found the enrichment of WRKY transcription factor binding sites in 5'-regulatory regions in conserved and species-specific responsive genes, linking the emergence of WRKY-binding sites with the evolution of gene responses in PTI. Our findings advance our understanding of transcriptome evolution during biotic stress.

中文翻译：

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拟南芥内和十字花科物种间模式触发免疫的基因表达进化

植物通过感测与微生物相关的分子模式（MAMP）来激活模式触发的免疫（PTI），从而识别周围的微生物。尽管它们对微生物控制具有重要意义，但PTI反应的演变仍未完全表征。利用六个拟南芥种质和三个其他十字花科植物对MAMP flg22的PTI反应的比较转录组学，我们鉴定了一组在纯化选择后的十字花科植物种中具有表达变化的基因，并显示出具有物种特异性表达特征的基因。十字花科物种的flg22触发的转录组和代谢组反应的变异与它们的系统发育不相符，而拟南芥中的表达变化则强烈保守，表明某些物种特异性基因表达的方向选择。我们发现WRKY转录因子结合位点在保守和物种特异性响应基因的5'调控区域富集，将WRKY结合位点的出现与PTI基因反应的发展联系起来。我们的发现提高了我们对生物应激期间转录组进化的理解。