14-3-3 λ protein interacts with ADF1 to regulate actin cytoskeleton dynamics in Arabidopsis

Actin cytoskeleton dynamics is critical for variety of cellular events including cell elongation, division and morphogenesis, and is tightly regulated by numerous groups of actin binding proteins. However it is not well understood how these actin binding proteins are modulated in a physiological condition by their interaction proteins. In this study, we describe that Arabidopsis 14-3-3 lambda protein interacted with actin depolymerizing factor 1 (ADF1) in plant to regulate F-actin stability and dynamics. Loss of 14-3-3 lambda in Arabidopsis resulted in longer etiolated hypocotyls in dark and changed actin cytoskeleton architecture in hypocotyl cells. Overexpression of ADF1 repressed 14-3-3 lambda mutant hypocotyl elongation and actin dynamic phenotype. In addition, the phosphorylation level of ADF1 was increased and the subcellular localization of ADF1 was altered in 14-3-3 lambda mutant. Consistent with these observations, the actin filaments were more stable in 14-3-3 lambda mutant. Our results indicate that 14-3-3 lambda protein mediates F-actin dynamics possibly through inhibiting ADF1 phosphorylation in vivo.