RRC ID 21600
Author Nozaki H, Onishi K, Morita E.
Title Differences in pyrenoid morphology are correlated with differences in the rbcL genes of members of the Chloromonas lineage (volvocales, chlorophyceae).
Journal J. Mol. Evol.
Abstract Chloromonas is distinguished from Chlamydomonas primarily by the absence of pyrenoids, which are structures that are present in the chloroplasts of most algae and are composed primarily of the CO2-fixing enzyme Rubisco. In this study we compared sequences of the rbcL (Rubisco large subunit-encoding) genes of pyrenoid-less Chloromonas species with those of closely related pyrenoid-containing Chlamydomonas species in the "Chloromonas lineage" and with those of 45 other green algae. We found that the proteins encoded by the rbcL genes had a much higher level of amino acid substitution in members of the Chloromonas lineage than they did in other algae. This kind of elevated substitution rate was not observed, however, in the deduced proteins encoded by two other chloroplast genes that we analyzed: atpB and psaB. The rates of synonymous and nonsynonymous nucleotide substitutions in the rbcL genes indicate that the rapid evolution of these genes in members of the Chloromonas lineage is not due to relaxed selection (as it presumably is in parasitic land plants). A phylogenetic tree based on rbcL nucleotide sequences nested two Chlamydomonas species as a "pyrenoid-regained" clade within a monophyletic Chloromonas "pyrenoid-lost" clade. Character-state optimization with this tree suggested that the loss and the regain of pyrenoids were accompanied by eight synapomorphic amino acid replacements in the Rubisco large subunit, four of which are positioned in the region involved in its dimerization. However, both the atpB and the psaB sequence data gave robust support for a rather different set of phylogenetic relationships in which neither the "pyrenoid-lost" nor the "pyrenoid-regained" clade was resolved. The appearance of such clades in the rbcL-based tree may be an artifact of convergent evolutionary changes that have occurred in a region of the large subunit that determines whether Rubisco molecules will aggregate to form a visible pyrenoid.
Volume 55(4)
Pages 414-30
Published 2002-10
DOI 10.1007/s00239-002-2338-9
PMID 12355262
MeSH Amino Acid Substitution Animals Chlamydomonas / genetics* Chlamydomonas / ultrastructure Chloroplasts* Evolution, Molecular Genetic Variation* Likelihood Functions Phylogeny Point Mutation Ribulose-Bisphosphate Carboxylase / genetics*
IF 1.957
Times Cited 26
Algae NIES-144 NIES-447 NIES-213 NIES-418 NIES-456 NIES-446 NIES-522 NIES-421 NIES-428 NIES-432 NIES-425 NIES-439 NIES-474 NIES-582 NIES-571 NIES-569 NIES-564 NIES-574 NIES-566 NIES-567 NIES-653 NIES-968 NIES-732 NIES-851 NIES-861 NIES-875 NIES-882 NIES-883 NIES-96 NIES-858 NIES-123