Abstract
Bacteria use signal transduction systems to sense and respond to their external environment. The two‐component system CpxA/CpxR senses misfolded envelope protein stress and responds by up‐regulating envelope protein factors and down‐regulating virulence factors in several animal pathogens.
Dickeya dadantii
is a phytopathogen equipped with a type III secretion system (T3SS) for manipulating the host immune response. We found that deletion of
cpxR
enhanced the expression of the T3SS marker gene
hrpA
in a designated T3SS‐inducing minimal medium (MM). In the ∆
cpxR
mutant, multiple T3SS and c‐di‐GMP regulators were also up‐regulated. Subsequent analysis revealed that deletion of the phosphodiesterase gene
egcpB
in ∆
cpxR
abolished the enhanced T3SS expression. This suggested that CpxR suppresses EGcpB levels, causing low T3SS expression in MM. Furthermore, we found that the ∆
cpxR
mutant displayed low c‐di‐GMP phenotypes in biofilm formation and swimming. Increased production of cellular c‐di‐GMP by in trans expression of the diguanylate cyclase gene
gcpA
was negated in the ∆
cpxR
mutant. Here, we propose that CpxA/CpxR regulates T3SS expression by manipulating the c‐di‐GMP network, in turn modifying the multiple physiological activities involved in the response to environmental stresses in
D. dadantii
.
The stress response regulator CpxR modulates T3SS expression and multiple physiological activities by manipulating the c‐di‐GMP network in the phytopathogen
Dickeya dadantii
.