Phylogenetic Patterns of Codon Evolution in the ACTIN-DEPOLYMERIZING FACTOR/COFILIN (ADF/CFL) Gene Family

The actin-depolymerizing factor/cofilin (ADF/CFL) gene family encodes a diverse group of relatively small proteins. Once known strictly as modulators of actin filament dynamics, recent research has demonstrated that these proteins are involved in a variety of cellular processes, from signal transduction to the cytonuclear trafficking of actin. In both plant and animal lineages, expression patterns of paralogs in the ADF/CFL gene family vary among tissue types and developmental stages. In this study we use computational approaches to investigate the evolutionary forces responsible for the diversification of the ADF/CFL gene family. Estimating the rate of non-synonymous to synonymous mutations (dN/dS) across phylogenetic lineages revealed that the majority of ADF/CFL codon positions were under strong purifying selection, with rare episodic events of accelerated protein evolution. In both plants and animals these instances of accelerated evolution were ADF/CFL subclass specific, and all of the sites under selection were located in regions of the protein that could serve in new functional roles. We suggest these sites may have been important in the functional diversification of ADF/CFL proteins.

肌动蛋白去聚合因子/肌动蛋白结合蛋白（ADF/CFL）基因家族编码一组相对较小的蛋白质。昔日，这些蛋白质仅被严格视为肌动蛋白丝动态的调节因子，但近期研究揭示了这些蛋白质参与多种细胞过程，涵盖信号转导至肌动蛋白的细胞核质转运。在植物和动物谱系中，ADF/CFL基因家族中的同源基因在组织类型和发育阶段上的表达模式各不相同。本研究采用计算方法，探究导致ADF/CFL基因家族多样化演化的进化力量。通过估计不同谱系中非同义突变与同义突变的比率（dN/dS），发现ADF/CFL密码子位置大多数受到强烈的净化选择，仅有少数加速蛋白进化的偶发事件。在植物和动物中，这些加速进化的实例均为ADF/CFL亚类特异性，且所有处于选择状态的位点均位于蛋白质可能发挥新功能作用区域。我们推测，这些位点可能在ADF/CFL蛋白的功能多样化过程中发挥了重要作用。