Rate variation as a function of gene origin in plastid-derived genes of peridinin-containing dinoflagellates.
Peridinin-pigmented dinoflagellates contain secondary plastids that seem to have undergone more nearly complete plastid genome reduction than other eukaryotes. Many typically plastid-encoded genes appear to have been transferred to the nucleus, with a few remaining genes found on minicircles. To understand better the evolution of the dinoflagellate plastid, four categories of plastid-associated genes in dinoflagellates were defined based on their history of transfer and evaluated for rate of sequence evolution, including minicircle genes (presumably plastid-encoded), genes probably transferred from the plastid to the nucleus (plastid-transferred), and genes that were likely acquired directly from the nucleus of the previous plastid host (nuclear-transferred). The fourth category, lateral-transferred genes, are plastid-associated genes that do not appear to have a cyanobacterial origin. The evolutionary rates of these gene categories were compared using relative rate tests and likelihood ratio tests. For comparison with other secondary plastid-containing organisms, rates were calculated for the homologous sequences from the haptophyte Emiliania huxleyi. The evolutionary rate of minicircle and plastid-transferred genes in the dinoflagellate was strikingly higher than that of nuclear-transferred and lateral-transferred genes and, also, substantially higher than that of all plastid-associated genes in the haptophyte. Plastid-transferred genes in the dinoflagellate had an accelerated rate of evolution that was variable but, in most cases, not as extreme as the minicircle genes. Furthermore, the nuclear-transferred and lateral-transferred genes showed rates of evolution that are similar to those of other taxa. Thus, nucleus-to-nucleus transferred genes have a more typical rate of sequence evolution, while those whose history was wholly or partially within the dinoflagellate plastid genome have a markedly accelerated rate of evolution.
Bachvaroff
Tsvetan R
TR
Department of Cell Biology and Molecular Genetics, University of Maryland College Park, H. J. Patterson Hall, College Park, MD 20742, USA.
Sanchez-Puerta
M Virginia
MV
Delwiche
Charles F
CF
D000818:Animals; D002338:Carotenoids / Q000235:genetics*; D004141:Dinoflagellida / Q000235:genetics*; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal; D014644:Genetic Variation; D018087:Plastids / Q000235:genetics*
C016040:peridinin; D002338:Carotenoids