LIM Proteins: A Novel Class of Actin Cytoskeleton Organizers in Plants

The eukaryotic LIM domain defines a double zinc-finger like structure that functions as a protein-protein interaction module. Whereas in animals the LIM domain is found in numerous proteins of diverse functions, plants possess only a limited number of LIM domain-containing proteins (LIMs). It is noteworthy that most of plant LIMs belong to a same family that is structurally related to the animal Cysteine-Rich Proteins (CRPs). In the September issue of The Plant Cell, we have provided evidence that the tobacco WLIM1 is able to bind actin filaments in a direct manner, to stabilize them and to trigger actin bundling both in vitro and in vivo. These data, together with recent reports on animal CRPs, strongly suggest that these proteins represent a novel class of actin cytoskeleton regulators. In this addendum, we give a brief history of the research that has been conducted on plant LIMs in our lab. Additionally, we show that the GFP-fused tobacco WLIM1 protein is able to properly localize when ectopically expressed in monkey Vero cells, indicating that, despite a relatively low degree of identity/similarity, animal CRPs and plant LIMs display a very similar actin binding activity.