Experimental-Evolution-Driven Identification of Arabidopsis Rhizosphere Competence Genes in Pseudomonas protegens

Abstract

Beneficial root-associated microorganisms carry out many functions that are essential for plant performance. Establishment of a bacterium on plant roots, however, requires overcoming many challenges.

Experimental evolution of Bacillus subtilis on Arabidopsis thaliana roots reveals fast adaptation and improved root colonization

“…In contrast to our observations, Li et al. (2021a) observed several evolved isolates of P. protegens improved in swimming motility following adaptation to the A. thaliana rhizosphere in a sand system ( Li et al., 2021b ), supporting that in sand (and thus possibly also in soil), motility is indeed important for root colonization and is therefore selected for.…”

“…From an applied perspective, experimental evolution of B. subtilis on plant roots represents an unexplored approach for developing strains with improved root attachment abilities for agricultural use. However, a biofilm-motility tradeoff as observed here may be undesirable when developing biocontrol agents owing to the growing evidence of motility as an important trait for bacterial root colonization in soil systems ( Li et al., 2021b ; Tian et al., 2021 ). The phenotypes associated with the adaptation of B. subtilis to A. thaliana roots presented here as well as the accompanying evolutionary cost and the increased root colonization also in the presence of resident soil bacteria highlight the importance of considering the selective environment if evolving PGPR for biocontrol purposes.…”

“…Several studies have reported experimental evolution as a powerful tool to explore how bacteria adapt to ecologically relevant environments. A recent study investigated the adaptive response of the PGPR Pseudomonas protegens to the A. thaliana rhizosphere in a sand system, which revealed mutations in genes encoding global regulators and genes related to motility and cell surface structure across independent populations ( Li et al., 2021b ) and during such adaptation, the initially plant-antagonistic P. protegens bacterium evolved into mutualists ( Li et al., 2021a ). Furthermore, Lin et al.…”

Diverse functions for acyltransferase-3 proteins in the modification of bacterial cell surfaces

“…The role of O-antigen modifications in plant–microbe interactions has also recently been discovered in the plant-root associated γ-proteobacterium Pseudomonas protegens CHA0, which contains an O-antigen cluster with an AT3–SGNH encoding gene present [65]. Evolution of improved rhizosphere competence by this bacterium appears to select for disruption of this gene, indicating that cell surface decoration plays some role in root-colonisation [66].…”

Innovative Rhizosphere-Based Enrichment under P-Limitation Selects for Bacterial Isolates with High-Performance P-Solubilizing Traits

“…Additionally, over the past decades, bacterial gene-expression during plant-bacterial interactions in the rhizosphere have been studied and reviewed, especially for Pseudomonas spp. The ability of bacterial species to thrive in the rhizosphere is not attributed to one unique genetic trait, but relies on diverse cellular pathways and physiological responses ( 39 – 41 ). In previous research, we optimized an iterative in planta method to enrich the maize rhizosphere for bacteria that have both the rhizosphere competence and the P-solubilization trait ( 38 ).…”