title: Alanyl-tRNA synthetase genes of Vanderwaltozyma polyspora arose from duplication of a dual-functional predecessor of mitochondrial origin.
abstract: In eukaryotes, the cytoplasmic and mitochondrial forms of a given aminoacyl-tRNA synthetase (aaRS) are typically encoded by two orthologous nuclear genes, one of eukaryotic origin and the other of mitochondrial origin. We herein report a novel scenario of aaRS evolution in yeast. While all other yeast species studied possess a single nuclear gene encoding both forms of alanyl-tRNA synthetase (AlaRS), Vanderwaltozyma polyspora, a yeast species descended from the same whole-genome duplication event as Saccharomyces cerevisiae, contains two distinct nuclear AlaRS genes, one specifying the cytoplasmic form and the other its mitochondrial counterpart. The protein sequences of these two isoforms are very similar to each other. The isoforms are actively expressed in vivo and are exclusively localized in their respective cellular compartments. Despite the presence of a promising AUG initiator candidate, the gene encoding the mitochondrial form is actually initiated from upstream non-AUG codons. A phylogenetic analysis further revealed that all yeast AlaRS genes, including those in V. polyspora, are of mitochondrial origin. These findings underscore the possibility that contemporary AlaRS genes in V. polyspora arose relatively recently from duplication of a dual-functional predecessor of mitochondrial origin.
authors: Department of Life Sciences, National Central University, Jungli 32001, Taiwan.
authors: Chia-Pei
authors: CP
authors: Chang
authors: Yi-Kuan
authors: YK
authors: Tseng
authors: Chou-Yuan
authors: CY
authors: Ko
authors: Chien-Chia
authors: CC
authors: Wang
mesh_terms: D000412:Alanine-tRNA Ligase / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D020029:Base Pairing; D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics; D018387:Codon, Initiator; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D020440:Gene Duplication; D005800:Genes, Fungal; D050259:Genes, Mitochondrial; D024101:Mitochondrial Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D012344:RNA, Transfer, Ala / Q000737:chemistry; D004718:Saccharomycetales / Q000201:enzymology* / Q000235:genetics*
chemical_list: D018387:Codon, Initiator; D005656:Fungal Proteins; D024101:Mitochondrial Proteins; D012344:RNA, Transfer, Ala; D000412:Alanine-tRNA Ligase