A Novel Transcription Factor Cder Regulates the Type III Secretion System in a c-di-GMP Dependent Manner in Dickeya Dadantii

Abstract

The enterobacterium, Dickeya dadantii, is an opportunistic bacterial pathogen that causes disease in many plants. C-di-GMP is a ubiquitous bacterial second messenger, regulating multiple cellular behaviors through several c-di- GMP-associated components. Here, we identified a novel transcriptional regulator named CdeR that regulates T3SS in a c-di-GMP-dependent manner. GcpD is a diguanylate cyclase responsible for the synthesis of c-di-GMP. Compared to a gcpD mutant, the gcpD and cdeR double mutant exhibited a reduced T3SS expression. In addition, we found that, under the gcpD mutant background, CdeR regulates T3SS by manipulating intracellular c-di-GMP levels, involving an additional diguanylate cyclase GcpL upregulated by CdeR. This is the first report that uncovers CdeR as a transcriptional regulator involved in the regulation of T3SS. A model is proposed on how CdeR regulates T3SS expression by manipulating the c-di-GMP network.