RT Journal
A1 Monier, Adam
A1 Pagarete, António
A1 de Vargas, Colomban
A1 Allen, Michael J.
A1 Read, Betsy
A1 Claverie, Jean-Michel
A1 Ogata, Hiroyuki
T1 Horizontal gene transfer of an entire metabolic pathway between a eukaryotic alga and its DNA virus
JF Genome Research 
JO Genome Research 
YR 2009 
FD August 01 
VO 19 
IS 8 
SP 1441 
OP 1449 
DO 10.1101/gr.091686.109 
UL http://genome.cshlp.org/content/19/8/1441.abstract 
AB Interactions between viruses and phytoplankton, the main primary producers in the oceans, affect global biogeochemical cycles and climate. Recent studies are increasingly revealing possible cases of gene transfers between cyanobacteria and phages, which might have played significant roles in the evolution of cyanobacteria/phage systems. However, little has been documented about the occurrence of horizontal gene transfer in eukaryotic phytoplankton/virus systems. Here we report phylogenetic evidence for the transfer of seven genes involved in the sphingolipid biosynthesis pathway between the cosmopolitan eukaryotic microalga Emiliania huxleyi and its large DNA virus EhV. PCR assays indicate that these genes are prevalent in E. huxleyi and EhV strains isolated from different geographic locations. Patterns of protein and gene sequence conservation support that these genes are functional in both E. huxleyi and EhV. This is the first clear case of horizontal gene transfer of multiple functionally linked enzymes in a eukaryotic phytoplankton–virus system. We examine arguments for the possible direction of the gene transfer. The virus-to-host direction suggests the existence of ancient viruses that controlled the complex metabolic pathway in order to infect primitive eukaryotic cells. In contrast, the host-to-virus direction suggests that the serial acquisition of genes involved in the same metabolic pathway might have been a strategy for the ancestor of EhVs to stay ahead of their closest relatives in the great evolutionary race for survival.