The Periplasmic Oxidoreductase DsbA Is Required for Virulence of the Phytopathogen Dickeya solani.

Tomasz Przepiora,Nicole Hugouvieux-Cotte-Pattat,Donata Figaj,Robert Czajkowski,Aleksandra Bogucka,Jakub Fikowicz-Krosko,Joanna Skorko-Glonek

doi:10.3390/ijms23020697

Abstract

In bacteria, the DsbA oxidoreductase is a crucial factor responsible for the introduction of disulfide bonds to extracytoplasmic proteins, which include important virulence factors. A lack of proper disulfide bonds frequently leads to instability and/or loss of protein function; therefore, improper disulfide bonding may lead to avirulent phenotypes. The importance of the DsbA function in phytopathogens has not been extensively studied yet. Dickeya solani is a bacterium from the Soft Rot Pectobacteriaceae family which is responsible for very high economic losses mainly in potato. In this work, we constructed a D. solani dsbA mutant and demonstrated that a lack of DsbA caused a loss of virulence. The mutant bacteria showed lower activities of secreted virulence determinants and were unable to develop disease symptoms in a potato plant. The SWATH-MS-based proteomic analysis revealed that the dsbA mutation led to multifaceted effects in the D. solani cells, including not only lower levels of secreted virulence factors, but also the induction of stress responses. Finally, the outer membrane barrier seemed to be disturbed by the mutation. Our results clearly demonstrate that the function played by the DsbA oxidoreductase is crucial for D. solani virulence, and a lack of DsbA significantly disturbs cellular physiology.

Highlights

The success of plant host infection by phytopathogenic bacteria depends on the coordinated action of numerous virulence factors and virulence determinants
Since secreted or envelope proteins are exposed to harsh environmental conditions, which may result in their rapid denaturation, their structure is frequently stabilized by disulfide (S-S) bonds formed between cysteine residues
To investigate the potential contribution of the DsbA protein in D. solani fitness and virulence, the dsbA gene of the D. solani IPO2222 chromosome was inactivated by marker exchange mutagenesis to produce the D. solani dsbA::cmR mutant (TP02) (Figure S1)

Summary

Introduction

The success of plant host infection by phytopathogenic bacteria depends on the coordinated action of numerous virulence factors and virulence determinants. In most cases, these factors are extracellular secreted proteins or proteins associated with the surface of a pathogen’s cell [1]. The ability of bacteria to survive various external stress factors is strictly linked with the correct functioning of the envelope as the cell/environment barrier. Since secreted or envelope proteins are exposed to harsh environmental conditions, which may result in their rapid denaturation, their structure is frequently stabilized by disulfide (S-S) bonds formed between cysteine residues. A lack of proper disulfide bonds in these proteins frequently results in unfolding, loss of function and subsequent protein degradation. Oxidoreductases of the Dsb (Disulfide bond) protein family are responsible for introducing proper S-S bonds between cysteine residues [2,3,4], reviewed in [5]

Objectives

Methods

Results

Discussion

Conclusion