GGS : Vol. 83 (2008) , No. 2 p.127-133

Molecular phylogeny and evolution of the plastid and nuclear encoded cbbX genes in the unicellular red alga Cyanidioschyzon merolae

Kiyohito Fujita¹⁾, Shigeki Ehira¹⁾, Kan Tanaka²⁾, Kei Asai¹⁾ and Niji Ohta¹⁾

1) Department of Molecular Biology, Faculty of Science, Saitama University
2) Institute of Molecular and Cellular Biosciences, The University of Tokyo

(Received December 12, 2007)
(Accepted December 28, 2007)

The cbbX gene is generally encoded in proteobacterial genomes and red-algal plastid genomes. In this study, we found two distinct cbbX genes of Cyanidioschyzon merolae, a unicellular red alga, one encoded in the plastid genome and the other encoded in the cell nucleus. The phylogenetic tree inferred from cbbX genes and strongly conserved gene organization (rbcLS-cbbX) suggests that the plastid-encoded cbbX gene of C. merolae came from an ancestral proteobacterium by horizontal gene transfer. On the other hand, the nuclear-encoded cbbX gene of C. merolae was classified in another cluster together with the nucleomorph-encoded cbbX gene of Guillardia theta. Furthermore, expression of the two cbbX genes were regulated differently in response to extracellular CO₂ concentration. Our results imply that cbbX gene in the plastid genome was copied and transferred to the cell nucleus after horizontal gene transfer of RuBisCo operon from ancestral β-proteobacteria at comparatively early stage, and that each cbbX evolved in different ways.

CbbX, C. merolae, molecular phylogeny

	To cite this article:
	Kiyohito Fujita, Shigeki Ehira, Kan Tanaka, Kei Asai and Niji Ohta. “Molecular phylogeny and evolution of the plastid and nuclear encoded cbbX genes in the unicellular red alga Cyanidioschyzon merolae” Genes Genet. Syst. Vol. 83 127-133 (2008) .

	doi:10.1266/ggs.83.127
	JOI JST.JSTAGE/ggs/83.127