Li Erqin, de Jonge Ronnie, Liu Chen, Jiang Henan, Friman Ville-Petri, Pieterse Corné M J, Bakker Peter A H M, Jousset Alexandre
Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands.
Freie Universität Berlin, Institut für Biologie, Berlin, Germany.
Nat Commun. 2021 Jun 22;12(1):3829. doi: 10.1038/s41467-021-24005-y.
While beneficial plant-microbe interactions are common in nature, direct evidence for the evolution of bacterial mutualism is scarce. Here we use experimental evolution to causally show that initially plant-antagonistic Pseudomonas protegens bacteria evolve into mutualists in the rhizosphere of Arabidopsis thaliana within six plant growth cycles (6 months). This evolutionary transition is accompanied with increased mutualist fitness via two mechanisms: (i) improved competitiveness for root exudates and (ii) enhanced tolerance to the plant-secreted antimicrobial scopoletin whose production is regulated by transcription factor MYB72. Crucially, these mutualistic adaptations are coupled with reduced phytotoxicity, enhanced transcription of MYB72 in roots, and a positive effect on plant growth. Genetically, mutualism is associated with diverse mutations in the GacS/GacA two-component regulator system, which confers high fitness benefits only in the presence of plants. Together, our results show that rhizosphere bacteria can rapidly evolve along the parasitism-mutualism continuum at an agriculturally relevant evolutionary timescale.
虽然有益的植物 - 微生物相互作用在自然界中很常见，但细菌共生进化的直接证据却很少。在这里，我们通过实验进化因果证明，最初对植物具有拮抗作用的荧光假单胞菌在六个植物生长周期（6个月）内在拟南芥根际进化为共生菌。这种进化转变通过两种机制伴随着共生适应性的提高：（i）对根系分泌物的竞争力增强；（ii）对植物分泌的抗菌物质东莨菪亭的耐受性增强，其产生受转录因子MYB72调控。至关重要的是，这些共生适应伴随着植物毒性降低、根系中MYB72转录增强以及对植物生长的积极影响。在基因方面，共生与双组分调节系统GacS/GacA中的多种突变相关，该系统仅在有植物存在时才赋予高适应性益处。总之，我们的结果表明，根际细菌可以在与农业相关的进化时间尺度上沿着寄生 - 共生连续体快速进化。
