Title:
The Chlorella variabilis NC64A Genome Reveals Adaptation to Photosymbiosis, Coevolution with Viruses, and Cryptic Sex
The Chlorella variabilis NC64A Genome Reveals Adaptation to Photosymbiosis, Coevolution with Viruses, and Cryptic Sex
Author(s)
Blanc, Guillaume
Duncan, Garry
Agarkova, Irina
Borodovsky, Mark
Gurnon, James
Kuo, Ala
Lindquist, Erika
Lucas, Susan
Pangilinan, Jasmyn
Polle, Juergen
Salamov, Asaf
Terry, Astrid
Yamada, Takashi
Dunigan, David D.
Grigoriev, Igor V.
Claverie, Jean-Michel
Van Etten, James L.
Duncan, Garry
Agarkova, Irina
Borodovsky, Mark
Gurnon, James
Kuo, Ala
Lindquist, Erika
Lucas, Susan
Pangilinan, Jasmyn
Polle, Juergen
Salamov, Asaf
Terry, Astrid
Yamada, Takashi
Dunigan, David D.
Grigoriev, Igor V.
Claverie, Jean-Michel
Van Etten, James L.
Advisor(s)
Editor(s)
Collections
Supplementary to
Permanent Link
Abstract
Chlorella variabilis NC64A, a unicellular photosynthetic green alga (Trebouxiophyceae), is an intracellular photobiont of Paramecium bursaria and a model system for studying virus/algal interactions. We sequenced its 46-Mb nuclear genome, revealing an expansion of protein families that could have participated in adaptation to symbiosis. NC64A exhibits variations in GC content across its genome that correlate with global expression level, average intron size, and codon usage bias. Although Chlorella species have been assumed to be asexual and nonmotile, the NC64A genome encodes all the known meiosis-specific proteins and a subset of proteins found in flagella. We hypothesize that Chlorella might have retained a flagella-derived structure that could be involved in sexual reproduction. Furthermore, a survey of phytohormone pathways in chlorophyte algae identified algal orthologs of Arabidopsis thaliana genes involved in hormone biosynthesis and signaling, suggesting that these functions were established prior to the evolution of land plants. We show that the ability of Chlorella to produce chitinous cell walls likely resulted from the capture of metabolic genes by horizontal gene transfer from algal viruses, prokaryotes, or fungi. Analysis of the NC64A genome substantially advances our understanding of the green lineage evolution, including the genomic interplay with viruses and symbiosis between eukaryotes.
Sponsor
Date Issued
2010-09
Extent
Resource Type
Text
Resource Subtype
Article