title: Molecular evolution of the actin-like MreB protein gene family in wall-less bacteria.
abstract: The mreB gene family encodes actin-like proteins that determine cell shape by directing cell wall synthesis and often exists in one to three copies in the genomes of non-spherical bacteria. Intriguingly, while most wall-less bacteria do not have this gene, five to seven mreB homologs are found in Spiroplasma and Haloplasma, which are both characterized by cell contractility. To investigate the molecular evolution of this gene family in wall-less bacteria, we sampled the available genome sequences from these two genera and other related lineages for comparative analysis. The gene phylogenies indicated that the mreB homologs in Haloplasma are more closely related to those in Firmicutes, whereas those in Spiroplasma form a separate clade. This finding suggests that the gene family expansions in these two lineages are the results of independent ancient duplications. Moreover, the Spiroplasma mreB homologs can be classified into five clades, of which the genomic positions are largely conserved. The inference of gene gains and losses suggests that there has been an overall trend to retain only one homolog from each of the five mreB clades in the evolutionary history of Spiroplasma.
authors.affiliation: Institute of Plant and Microbial Biology, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Chuan
authors.initials: C
authors.lastname: Ku
authors.affiliation: Institute of Plant and Microbial Biology, Academia Sinica, Taipei 115, Taiwan; Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, National Chung Hsing University and Academia Sinica, Taipei 115, Taiwan; Graduate Institute of Biotechnology, National Chung Hsing University, Taichung 402, Taiwan.
authors.forename: Wen-Sui
authors.initials: WS
authors.lastname: Lo
authors.affiliation: Institute of Plant and Microbial Biology, Academia Sinica, Taipei 115, Taiwan; Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, National Chung Hsing University and Academia Sinica, Taipei 115, Taiwan; Biotechnology Center, National Chung Hsing University, Taichung 402, Taiwan. Electronic address: chk@gate.sinica.edu.tw.
authors.forename: Chih-Horng
authors.initials: CH
authors.lastname: Kuo
mesh_terms: D000199:Actins / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D020440:Gene Duplication; D016680:Genome, Bacterial; D010802:Phylogeny; D013149:Spiroplasma / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D008973:Tenericutes / Q000166:cytology* / Q000235:genetics* / Q000378:metabolism
chemical_list: D000199:Actins; D001426:Bacterial Proteins
keywords: Cytoskeleton; Haloplasma; Mollicutes; Spiroplasma; Wall-less bacteria; mreB