Affiliation:
1. Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR 441-2594 INRA-CNRS, BP52627, F-31320 Castanet-Tolosan, France
Abstract
ABSTRACT
RpoE2 is an extracytoplasmic function (ECF) sigma factor involved in the general stress response of
Sinorhizobium meliloti
, the nitrogen-fixing symbiont of the legume plant alfalfa. RpoE2 orthologues are widely found among alphaproteobacteria, where they play various roles in stress resistance and/or host colonization. In this paper, we report a genetic and biochemical investigation of the mechanisms of signal transduction leading to
S. meliloti
RpoE2 activation in response to stress. We showed that RpoE2 activity is negatively controlled by two paralogous anti-sigma factors, RsiA1 (SMc01505) and RsiA2 (SMc04884), and that RpoE2 activation by stress requires two redundant paralogous PhyR-type response regulators, RsiB1 (SMc01504) and RsiB2 (SMc00794). RsiB1 and RsiB2 do not act at the level of
rpoE2
transcription but instead interact with the anti-sigma factors, and we therefore propose that they act as anti-anti-sigma factors to relieve RpoE2 inhibition in response to stress. This model closely resembles a recently proposed model of activation of RpoE2-like sigma factors in
Methylobacterium extorquens
and
Bradyrhizobium japonicum
, but the existence of two pairs of anti- and anti-anti-sigma factors in
S. meliloti
adds an unexpected level of complexity, which may allow the regulatory system to integrate multiple stimuli.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
59 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献