肌动蛋白与真核生物的进化

ACTIN AND EUKARYOTIC EVOLUTION

以肌动蛋白氨基酸取代与真核生物进化年代呈线性关系为依据，收集原生生物界、真菌界、植物界和动物界等四界74种生物的128个肌动蛋白序列，通过对其氨基酸序列同源性进行比较，制作出肌动蛋白的分子进化树，并依此进化树从分子水平对真核生物的进化进行一些探讨。从总体上看，肌动蛋白分子进化树较好地反映了真核生物间的进化关系，为确定某些生物的进化位置及进化关系提供了分子证据．

Actin, one of the most abundant proteins found in eukaryotic cells, is the major contractile component in myofibrils of muscle cells and the major cytoskeletal component of non-muscle cells. Comparison of the amino acid sequences from a wide range of eukaryotes shows that actin is extremely conserved during the eukaryotic evolution, and This work was supported by the National Natural Science Foundation of Chinacan be used for phylogenetic analysis. An actin phylogenetic tree relating 128 actin protein sequences from 74 organisms which representing protozoan, fungal, plant and animal kingdoms is constructed by the max amino acid homology method in this study. The major branches appear to match with the conventional taxonomic classifications. The protist, fungi, plants and animals form a distinct group in the phylogenetic tree.Protists are the most ancient and simple eukaryotic organisms, including protists and algae. They form an independent branch, the group firstly diverged from the main branch. Ciliophotus are the most divergent species in the tree. This implies that ciliophote may be the first species which evolved from the eukaryotic progenitors.oomycete was originally classified as a fungi, but recent studies based on its morphological and biochemical features have suggested that oomycetes evolved from a heterokont algal ancestor which lost chloroplasts. Our result shows that oomycetes are most closely related to brown alga, but are distinct from other fungi. This result supports above opinion. Moreover, the actin phylogenetic tree places slime molds closest to an amoebae. Since the phylogenetic relationship of slime molds to fungi and protists has been questioned, this data supports the grouping of slime molds with the protists.Plants have a relatively high divergence corresponding to fungi and animals. Because the data available only restricted to the higher plants, the evolution tendency of Plantae could not be shown on the tree.Animals are the most intensively studied eukaryote, and their evolution relationship could be seen clearly on the tree. Protostomia and Deuterostome form two distinct branch. And most of the animal evolution position correspond with traditional classifica tlon.Above analytic result shows that actin is a good candidate for studying the intraand interspecies evolution relationships of eukaryotes.