RRC ID 20169
Author Turmel M, Otis C, Lemieux C.
Title The complete mitochondrial DNA sequence of Mesostigma viride identifies this green alga as the earliest green plant divergence and predicts a highly compact mitochondrial genome in the ancestor of all green plants.
Journal Mol. Biol. Evol.
Abstract To gain insights into the nature of the mitochondrial genome in the common ancestor of all green plants, we have completely sequenced the mitochondrial DNA (mtDNA) of Mesostigma viride. This green alga belongs to a morphologically heterogeneous class (Prasinophyceae) that includes descendants of the earliest diverging green plants. Recent phylogenetic analyses of ribosomal RNAs (rRNAs) and concatenated proteins encoded by the chloroplast genome identified Mesostigma as a basal branch relative to the Streptophyta and the Chlorophyta, the two phyla that were previously thought to contain all extant green plants. The circular mitochondrial genome of Mesostigma resembles the mtDNAs of green algae occupying a basal position within the Chlorophyta in displaying a small size (42,424 bp) and a high gene density (86.6% coding sequences). It contains 65 genes that are conserved in other mtDNAs. Although none of these genes represents a novel coding sequence among green plant mtDNAs, four of them (rps1, sdh3, sdh4, and trnL[caa]) have not been reported previously in chlorophyte mtDNAs, and two others (rpl14 and trnI[gau]) have not been identified in the streptophyte mtDNAs examined so far (land-plant mtDNAs). Phylogenetic analyses of 19 concatenated mtDNA-encoded proteins favor the hypothesis that Mesostigma represents the earliest branch of green plant evolution. Four group I introns (two in rnl and two in cox1) and three group II introns (two in nad3 and one in cox2), two of which are trans-spliced at the RNA level, reside in Mesostigma mtDNA. The insertion sites of the three group II introns are unique to this mtDNA, suggesting that trans-splicing arose independently in the Mesostigma lineage and in the Streptophyta. The few structural features that can be regarded as ancestral in Mesostigma mtDNA predict that the common ancestor of all green plants had a compact mtDNA containing a minimum of 75 genes and perhaps two group I introns. Considering that the mitochondrial genome is much larger in size in land plants than in Mesostigma, we infer that mtDNA size began to increase dramatically in the Streptophyta either during the evolution of charophyte green algae or during the transition from charophytes to land plants.
Volume 19(1)
Pages 24-38
Published 2002-1
DOI 10.1093/oxfordjournals.molbev.a003979
PMID 11752187
MeSH Base Sequence Chlorophyta / cytology Chlorophyta / genetics* Cloning, Molecular Codon / genetics Conserved Sequence / genetics DNA, Mitochondrial / genetics* Evolution, Molecular Genes, Plant / genetics Genetic Code Genome* Introns / genetics Mitochondrial Proteins / chemistry Mitochondrial Proteins / genetics Molecular Sequence Data Nucleic Acid Conformation Phylogeny* Plant Cells Plants / classification Plants / genetics* RNA, Ribosomal, 5S / chemistry RNA, Ribosomal, 5S / genetics Sequence Homology, Nucleic Acid Species Specificity
IF 14.797
Times Cited 95
Algae NIES-296