Recently, State Key Laboratory of Agricultural Microbiology and team of Professor Kenichi Tsuda from College of Plant Science & Technology of HZAU published their latest research findings, which reveals the evolution of pattern-triggered immunity (PTI) across Brassicaceae species.
Despite the significance of variation in stress-responsive genes for plants’ adaptation to the environment, little is known about how stress-induced transcriptomic changes evolve in plants. Plants have evolved cell-surface localized pattern recognition receptors (PRR) that sense conserved micro-associated molecular patterns (MAMPs), leading to the activation of PTI. For example, oligopeptide flg22 at the N-terminal end of bacterial flagellin can be sensed by Flagellin Sensing 2 (FLS2), the receptor of Arabidopsis thaliana, eliciting a set of PTI responses including MAP kinase (MAPK) phosphorylation, genome-wide transcriptional reprogramming, and hormone synthesis, etc., thereby increasing resistance against pathogens. However, current understanding of PTI evolution is limited to the evolution of PRRs while the conservation of PTI responses among different species and how PTI responses evolve remain poorly comprehended.
Researchers put six Arabidopsis thaliana species and three Brassicaceae relatives (referred to Capsella rubella, Cardamine hirsute, and Eutrema salsugineum) upon fla22 treatment, observing that all four tested Brassicaceae species sensed flg22 to trigger typical early PTI responses though the physiological consequences, such as plant growth inhibition and bacterial resistance, varied across species.
Flg22-triggered transcriptional responses show a high degree of consistency among Arabidopsis thaliana accessions with diverse genetic backgrounds and geographical origins.
To study the evolution of transcriptomic changes during PTI responses, researchers made a comparative analysis of transcriptome responses after flg22 treatment of six Arabidopsis thaliana accessions and three Brassicaceae species, discovering there were a number of shared differentially expressed genes (DEGs) as well as quite a few species-specific DEGs among four Brassicaceae species. However, flg22-triggered transcriptional responses showed a high degree of conservation among Arabidopsis thaliana accessions with diverse genetic backgrounds and geographical origins. Interestingly, flg22-triggered responses were inconsistent with the phylogeny among Brassicaceae species, appealing researchers to further exploration. Results revealed that WRKY transcription factor binding motifs were highly enriched in the 5’-regulatory regions of species-specific flg22-responsive genes, which may drive the transcriptomic evolution of species-specific genes. Besides, it was also found that variation in coding sequences showed no strong correlation with transcriptome variation and purifying selection may have acted on the regulatory regions of conserved flg22-responsive genes across Brassicaceae species. Moreover, research findings indicated that metabolome profiles in response to flg22 varied with Brassicaceae species.
According to researchers, this research has revealed fundamental features of transcriptome evolution during PTI responses in Brassicaceae species and offered clues to further study on evolution of stress-induced transcriptomic changes in plants.
Translated by: Shang Meng
Supervised by: Xie Lujie
Source: http://news.hzau.edu.cn/2021/0308/59506.shtml
Article: https://academic.oup.com/plcell/advance-article/doi/10.1093/plcell/koab073/6159620?searchresult=1
