Cross-Talk Between Cognate and Noncognate RpoE Sigma Factors and Zn²⁺-Binding Anti-Sigma Factors Regulates Photooxidative Stress Response inAzospirillum brasilense

Abstract

The two redox-sensitive ZAS anti-σ factors in A. brasilense may interact with their cognate as well as noncognate ECF σ factors to play an important role in redox homeostasis by facilitating recovery from the oxidative stress.

Carotenoid Biosynthetic Pathways Are Regulated by a Network of Multiple Cascades of Alternative Sigma Factors in Azospirillum brasilense Sp7

“…On the basis of these as well as our previous observations (16,18), it can be hypothesized that the RpoEs may indirectly regulate crtE2 via RpoH1/RpoH2 to control carotenoid synthesis in A. brasilense, and if so, these RpoHs should be regulated directly or indirectly by RpoEs. Our data from the two-plasmid system reveal direct regulation of rpoH2 and rpoH5 by RpoE1 and of rpoH1 and rpoH4 by RpoE2 and confirm the occurrence of at least two cascades regulating crtE2, which include RpoE1¡RpoH2¡CrtE2 and RpoE2¡RpoH1¡CrtE2.…”

“…In our studies on the regulation of carotenoid biosynthesis in A. brasilense, we have shown earlier that two ECF sigma factors, RpoE1 and RpoE2, positively regulate carotenoid synthesis in A. brasilense Sp7 (16)(17)(18)25). Whether carotenoid biosynthetic genes are controlled directly or indirectly by RpoEs was not known.…”

“…Our previous study showed that A. brasilense RpoE1 and RpoE2 are highly homologous, and hence, they not only regulate carotenoid synthesis but also regulate the expression of several common genes in A. brasilense (18). Data from this work show that although RpoE1 and RpoE2 both regulate carotenoid biosynthesis in A. brasilense, they bring about this regulation through different RpoH sigma factors (RpoE1 regulating RpoH2/5 and RpoE2 regulating RpoH1/4), indicating recognition of different promoters by the two RpoEs.…”

“…It synthesizes bacterioruberin-type carotenoids (15). Recently, we reported that carotenoid synthesis is induced by light and regulated by a pair of ECF sigma factors (RpoE1 and RpoE2) in this bacterium (16)(17)(18). In addition, we have also shown that a heat shock sigma factor (RpoH2, or H ) is involved in the photooxidative stress response in this bacterium (19).…”

Studies of the extracytoplasmic function sigma factor PG0162 in Porphyromonas gingivalis

“…Other ECF sigma factors and transcriptional regulators were upregulated in P. gingivalis FLL391, indicating that the PG0162 ECF sigma factor could be part of a complex regulatory signaling network in P. gingivalis . Cross talks among bacterial regulatory networks have been shown to have important physiological consequences that are vital for microbial survival/pathogenesis (Coggan & Wolfgang, ; Gupta et al ., ). Although it is not yet confirmed, we cannot rule out the likelihood of cross talk between the PG0162 ECF sigma factor and the different regulatory networks.…”