Pleiotropic effects of RsmA and RsmE proteins in Pseudomonas fluorescens 2P24

Yang Zhang,Li-Qun Zhang,Haiyan Wu,Bo Zhang,Qing Yan,Xiaogang Wu

doi:10.1186/s12866-020-01880-x

Abstract

BackgroundPseudomonas fluorescens 2P24 is a rhizosphere bacterium that produces 2,4-diacetyphloroglucinol (2,4-DAPG) as the decisive secondary metabolite to suppress soilborne plant diseases. The biosynthesis of 2,4-DAPG is strictly regulated by the RsmA family proteins RsmA and RsmE. However, mutation of both of rsmA and rsmE genes results in reduced bacterial growth.ResultsIn this study, we showed that overproduction of 2,4-DAPG in the rsmA rsmE double mutant influenced the growth of strain 2P24. This delay of growth could be partially reversal when the phlD gene was deleted or overexpression of the phlG gene encoding the 2,4-DAPG hydrolase in the rsmA rsmE double mutant. RNA-seq analysis of the rsmA rsmE double mutant revealed that a substantial portion of the P. fluorescens genome was regulated by RsmA family proteins. These genes are involved in the regulation of 2,4-DAPG production, cell motility, carbon metabolism, and type six secretion system.ConclusionsThese results suggest that RsmA and RsmE are the important regulators of genes involved in the plant-associated strain 2P24 ecologic fitness and operate a sophisticated mechanism for fine-tuning the concentration of 2,4-DAPG in the cells.

Highlights

Pseudomonas fluorescens 2P24 is a rhizosphere bacterium that produces 2,4-diacetyphloroglucinol (2,4-DAPG) as the decisive secondary metabolite to suppress soilborne plant diseases
P. fluorescens 2P24, a rhizospheric bacterium originally isolated from the take-all decline soil, has been investigated for its ability to produce the secondary metabolite 2,4-diacetylphloroglucinol (2,4-DAPG), which contributes to the protection of various crop plants against soil borne disease caused by many plant pathogens [16]
High concentration of 2,4-DAPG in the cells impaired the growth of the rsmA rsmE double mutant Previous study showed that the growth of the rsmA rsmE double mutant was severely impaired compared with the wild-type strain 2P24

Summary

Introduction

Pseudomonas fluorescens 2P24 is a rhizosphere bacterium that produces 2,4-diacetyphloroglucinol (2,4-DAPG) as the decisive secondary metabolite to suppress soilborne plant diseases. The biosynthesis of 2,4-DAPG is strictly regulated by the RsmA family proteins RsmA and RsmE Mutation of both of rsmA and rsmE genes results in reduced bacterial growth. An important element in this complex regulatory network is the Gac/Rsm cascade pathway [1] This pathway is conserved in numerous Gramnegative bacteria and mediates the post-transcriptional regulation of diverse genes required for bacterial virulence and metabolism [2]. These include genes for the expression of extracellular enzymes [3], carbon storage compounds [4], Zhang et al BMC Microbiology (2020) 20:191. The products of phlACB genes are together required for the transacetylation of PG to monoacetylphloroglucinol (MAPG) and 2,4-DAPG [19]

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