Plastin (also know as fimbrin) orthologues can be found from lower eukaryotes to humans ( Delanote et al., 2005). As such, our goal in this study was to address how cross-linking affects the architecture of the cortex and its capacity to drive contractility-dependent processes in vivo. Although the role of F-actin cross-linking proteins has been extensively studied in vitro ( Wachsstock et al., 1994 Gardel et al., 2004 Delanote et al., 2005 Wagner et al., 2006 Murrell and Gardel, 2012), their function in the cortex of animal cells is still poorly understood.

Such structural plasticity is made possible by the capability of actin to be polymerized and depolymerized, bundled and cross-linked, and anchored to the plasma membrane by a multitude of actin-binding proteins ( Skop et al., 2004 Salbreux et al., 2012 Fievet et al., 2013). The cortex in these processes undergoes constant remodeling and is capable of forming complex higher-order structures ( Stossel et al., 2006 Tse et al., 2011). We propose that by increasing the connectivity of the F-actin meshwork, plastin enables the cortex to generate stronger and more coordinated forces to accomplish cellular morphogenesis.Īctomyosin-mediated cortical contractility is essential for a large number of force-dependent biological processes, from polarization and cytokinesis at the single-cell level to wound healing and embryo morphogenesis at the multicellular level ( Maddox et al., 2005 Lecuit and Lenne, 2007 Levayer and Lecuit, 2012 Salbreux et al., 2012 Munjal and Lecuit, 2014 Zaidel-Bar et al., 2015). Moreover, mathematical modeling showed that an optimal amount of bundling agents enhanced the ability of a network to contract. In the absence of PLST-1, polarization was compromised, cytokinesis was delayed or failed, and 50% of embryos died during development. PLST-1 was enriched in contractile structures and was required for effective coalescence of NMY-2 filaments into large contractile foci and for long-range coordinated contractility in the cortex. Here, we show that the evolutionarily conserved actin bundling/cross-linking protein plastin is instrumental for the generation of potent cortical actomyosin contractility in the Caenorhabditis elegans zygote. The role of actin cross-linking proteins in cortical dynamics is still incompletely understood. The cell cortex is essential to maintain animal cell shape, and contractile forces generated within it by nonmuscle myosin II (NMY-2) drive cellular morphogenetic processes such as cytokinesis.

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