Molecular evolution and functional characterization of the Arabidopsis thaliana actin-depolymerizing factor gene family
Roy-Zokan, Eileen Melanie
MetadataShow full item record
The actin cytoskeleton is an essential component of eukaryotic cells and has had a profound impact on the evolution of multicellular organisms. The Actin-Depolymerizing Factor/Cofilin (ADF/CFL) gene family encode for a group of proteins that serve in modulating actin filament dynamics. The ADF/CFL family of proteins are implicated in a variety of cellular processes such as lipid and membrane metabolism, mitochondrial dependent apoptosis, chemotaxis, and the cytonuclear trafficking of actin into the nucleus. Within Arabidopsis, there are 11 paralogous ADF proteins that partition into four ancient phylogenetic subclasses that are differentially regulated. The goal of the work presented here was to investigate the evolutionary processes that shaped the diversification of the Arabidopsis ADF gene family and to determine the degree of functional divergence between family members. By estimating selective pressure across the plant ADF and animal CFL gene phylogenies, I show that there are differing patterns of codon evolution specific to subclasses of plant ADFs as well as to the different classes of animal ADF/CFL variants. Efforts to characterize the functional role of the single subclass IV Arabidopsis ADF variant, ADF6, revealed that ADF6 most likely represents a non-essential member of the ADF gene family. Additionally, crossing adf9-1 with adf6-1 revealed that ADF6 acts in an antagonistic way with ADF9 to regulate flowering time. This role of ADF6 in flowering time is completely dependent on ADF9, as adf6-1 flowers normally and shows no alteration in expression of any of the key flowering time genes. Finally, performing a series of suppression studies with reconstructed ancestral proteins revealed that the Arabidopsis ADF family members have rapidly diverged in function post-duplication.