“…Phosphorylation of RLC on Ser19, and subsequently Thr18 (T18-P; S19-P), upregulates MII complex contractility by 60-to 1000-fold in various assays and can increase assembly of MII complexes into mini-filaments, thereby regulating production of force and modulating actin-crosslinking activity (Aad et al, 2015;Sellers, 1985Sellers, , 1991Somlyo and Somlyo, 2003;Trybus, 1989;Vasquez et al, 2014;Wendt et al, 2001). Whereas both wtRLC-and pnRLC-rescued morphants exhibit stabilization of the MII complex, only wtRLC rescues blastopore closure and convergence force production, indicating a strong dependence of these force-production events on RLC phosphorylation.…”