Email updates

Keep up to date with the latest news and content from BMC Genomics and BioMed Central.

Open Access Research article

Plastid and mitochondrion genomic sequences from Arctic Chlorella sp. ArM0029B

Haeyoung Jeong1, Jong-Min Lim1, Jihye Park2, Young Mi Sim1, Han-Gu Choi3, Jungho Lee2* and Won-Joong Jeong1*

Author Affiliations

1 Korea Research Institute of Bioscience and Biotechnology (KRIBB), 111 Gwahangno, Yuseong-gu, Daejeon 305-806, South Korea

2 Green Plant Institute, #2-202 Biovalley, 89 Seoho-ro, Kwonseon-gu, Suwon, South Korea

3 Korea Polar Research Institute, KIOST, 26 Songdomirae-ro, Yeonsu-gu, Incheon 406-840, South Korea

For all author emails, please log on.

BMC Genomics 2014, 15:286  doi:10.1186/1471-2164-15-286

Published: 16 April 2014

Abstract

Background

Chorella is the representative taxon of Chlorellales in Trebouxiophyceae, and its chloroplast (cp) genomic information has been thought to depend only on studies concerning Chlorella vulgaris and GenBank information of C. variablis. Mitochondrial (mt) genomic information regarding Chlorella is currently unavailable. To elucidate the evolution of organelle genomes and genetic information of Chlorella, we have sequenced and characterized the cp and mt genomes of Arctic Chlorella sp. ArM0029B.

Results

The 119,989-bp cp genome lacking inverted repeats and 65,049-bp mt genome were sequenced. The ArM0029B cp genome contains 114 conserved genes, including 32 tRNA genes, 3 rRNA genes, and 79 genes encoding proteins. Chlorella cp genomes are highly rearranged except for a Chlorella-specific six-gene cluster, and the ArM0029B plastid resembles that of Chlorella variabilis except for a 15-kb gene cluster inversion. In the mt genome, 62 conserved genes, including 27 tRNA genes, 3 rRNA genes, and 32 genes encoding proteins were determined. The mt genome of ArM0029B is similar to that of the non-photosynthetic species Prototheca and Heicosporidium. The ArM0029B mt genome contains a group I intron, with an ORF containing two LAGLIDADG motifs, in cox1. The intronic ORF is shared by C. vulgaris and Prototheca. The phylogeny of the plastid genome reveals that ArM0029B showed a close relationship of Chlorella to Parachlorella and Oocystis within Chlorellales. The distribution of the cox1 intron at 721 support membership in the order Chlorellales. Mitochondrial phylogenomic analyses, however, indicated that ArM0029B shows a greater affinity to MX-AZ01 and Coccomyxa than to the Helicosporidium-Prototheca clade, although the detailed phylogenetic relationships among the three taxa remain to be resolved.

Conclusions

The plastid genome of ArM0029B is similar to that of C. variabilis. The mt sequence of ArM0029B is the first genome to be reported for Chlorella. Chloroplast genome phylogeny supports monophyly of the seven investigated members of Chlorellales. The presence of the cox1 intron at 721 in all four investigated Chlorellales taxa indicates that the cox1 intron had been introduced in early Chorellales as a cis-splice form and that the cis-splicing intron was inherited to recent Chlorellales and was recently trans-spliced in Helicosporidium.