H2O2 modulates RHO-1/Rho activity in the contractile tissue of the C. elegans spermatheca. Both exogenous and endogenously generated H2O2 decrease spermathecal contractility by inhibition of RHO-1 through oxidation of Cys 20. Regulation of H2O2 levels in the spermatheca depends on the activity of the cytosolic superoxide dismutase SOD-1.

Actomyosin based contractility in smooth muscle and non-muscle cells is regulated by signaling through the small GTPase Rho and by calcium-activated pathways. We use the myoepithelial cells of the Caenorhabditis elegans spermatheca to study the mechanisms of coordinated myosin activation in vivo. Here, we demonstrate that redox signaling regulates RHO-1/Rho activity in this contractile tissue. Exogenous hydrogen peroxide treatment decreases spermathecal contractility by inhibiting RHO-1, which is mediated through a conserved cysteine in its active site (C20). Further, we identify a gradient of oxidation across the spermathecal tissue, which is regulated by the cytosolic superoxide dismutase, SOD-1. SOD-1 functions in the Rho pathway to inhibit RHO-1 through oxidation of C20. Our results suggest that SOD-1 functions to regulate the redox environment and to fine-tune Rho activity across the spermatheca.