Experimental evolution of plant rhizobacteria reveals emerging adaptive mutations

Abstract

The colonization capability of plant growth-promoting rhizobacteria (PGPRs) in the rhizosphere is essential for their beneficial effects on plant growth, yet the evolutionary processes and adaptive potential of PGPRs in this environment remain underexplored. Here, we established an experimental evolution system for the wheat rhizosphere using Pseudomonas bijieensis 2P24 (former name: Pseudomonas fluorescens 2P24) as a model, simulating its natural evolution and tracking its genomic alterations to uncover adaptive mutations. Whole-genome sequencing and single-nucleotide polymorphism analysis revealed the accumulation of mutations in the flagella-associated gene fleN during evolution, reaching 49% frequency in the final communities. These mutations increased the number of bacterial flagella, which in turn enhanced motility and colonization capacity in the wheat rhizosphere compared to the ancestral strain. This study represents the first investigation of PGPR adaptive evolution in the wheat rhizosphere, providing a system for studying plant-associated bacteria and insights into selecting and engineering PGPR strains for agricultural applications.