OpaR exerts a dynamic control over c-di-GMP homeostasis andcpsAexpression inV. parahaemolyticusthrough its regulation of ScrC and the trigger phosphodiesterase TpdA

Abstract

The second messenger cyclic dimeric guanosine monophosphate (c-di-GMP) plays a central role in controlling decision making processes of vital importance for the environmental survival of the human pathogenVibrio parahaemolyticus. The mechanisms by which c-di-GMP levels are dynamically controlled inV. parahaemolyticusare poorly understood. Here we report our findings regarding the involvement of OpaR in controlling c-di-GMP metabolism in planktonic and surface-attached cells through controlling the expression of the trigger phosphodiesterase (PDE) TpdA and other PDEs such as ScrC. Our results revealed that OpaR negatively modulates the expression oftpdAby maintaining a baseline level of c-di-GMP. The OpaR-regulated PDEs ScrC, ScrG and VP0117 enable the upregulation oftpdA, to a different degree, in the absence of OpaR. We also found that TpdA plays the dominant role in c-di-GMP degradation under planktonic conditions compared to the other OpaR-regulated PDEs. In cells growing over solid media the dominant c-di-GMP degrader role is played by ScrC for 72 hours and passes to TpdA after 96 hours of growth. We also report negative and positive effects of the absence of OpaR oncpsAexpression in cells growing over solid media or forming biofilms over glass, respectively. These results suggest that OpaR can act as a double-edged sword to control c-di-GMP accumulation andcpsAexpression positively or negatively in response to poorly understood environmental factors. Finally, through an in-silico analysis we point out outlets of the OpaR regulatory module that can impact decision making during the motile to sessile transition inV. parahaemolyticus.

Regulators H-NS and LeuO inversely control swarming motility and biofilm formation inVibrio parahaemolyticus

“…The present study shows that H-NS regulation of these phenotypes involves LeuO and their regulation of swarming genes laf and scrABC and biofilm genes cpsA-K and their regulator cpsR . In V. parahaemolyticus , it was shown that OpaR (the HapR homolog) is a positive regulator of CPS production and a negative regulator of swarming motility due to the positive effects of OpaR on c-di-GMP levels and cps expression (12, 28–30, 58–63) (64). In a Δ opaR mutant, the expression of cpsA , cpsR, and cpsQ is downregulated in V. parahaemolyticus indicating OpaR is a positive regulator of CPS and biofilm formation (14, 60).…”

The LuxO-OpaR quorum-sensing cascade differentially controls Vibriophage VP882 lysis-lysogeny decision making in liquid and on surfaces

“…S6B). This apparent inconsistency cannot simply be explained by ScrABC activation being restricted to surface growth because TpdA, a phosphodiesterase that is highly active in planktonic cells (24), was also capable of driving φVP882 lysogenic conversion of RIMD (Fig. 4C).…”

“…Following the same logic as above, perhaps the Qrr sRNAs only drive lysogenic conversion in planktonic cells because their downstream target is a planktonic-specific factor(s). Possessing surface growth- and planktonic growth-specific intermediate factors could provide RIMD an effective mechanism to confine the influences of the Qrr sRNAs and c-di-GMP abundance to their respective physical contexts despite both the Qrr sRNAs and c-di-GMP having other roles in planktonic and surface-associated cells (22,24,44).…”

“…Degradation of c-di-GMP reduces the c-di-GMP pool, which activates production of lateral flagella and swarming motility (15,16). Other phosphodiesterases (ScrG and TpdA) and diguanylate cyclases (ScrJ, ScrL, and GefA) also modulate these behaviors, with ScrABC functioning as the primary controller of c-di-GMP abundance during growth on a surface (20)(21)(22)(23)(24). Regarding the connection between QS and surface sensing, OpaR represses scrABC and thus, suppresses swarming motility at high cell density (10; and Fig.…”