Phylogenomic analysis of Emiliania huxleyi provides evidence for haptophyte-stramenopile association and a chimeric haptophyte nuclear genome.
Mar Genomics. 2015 Mar 4;
Authors: Miller JJ, Delwiche CF
Emiliania huxleyi is a haptophyte alga of uncertain phylogenetic affinity containing a secondarily derived plastid. We sought to characterize its relationships with other taxa by quantifying the bipartitions in which it was included from a group of single protein phylogenetic trees. The largest number of sequences supported a phylogenetic relationship of E. huxleyi with the stramenopiles, in particular Aureococcus anophagefferens. Far fewer nuclear sequences gave strong support to the placement of this coccolithophorid with the cryptophyte, Guillardia theta. The majority of the sequences that did support this relationship did not have plastid related functions. This result along with the previously supported phylogenetic association of haptophyte and cryptophyte plastids could be explained by the haptophyte acquisition of its plastid from a cryptophyte. Another small set of genes associated E. huxleyi with the Viridiplantae with high support, none of these had plastid related functions. Although it is possible that these genes are the result of the original plastid acquisition from a member of the Archaeplastida, our result could also be explained by haptophytes having at some point fed upon green algae. This study also identified several genes that may have been transferred from the haptophyte lineage to the dinoflagellates Karenia brevis and Karlodinium veneficum as a result of their haptophyte derived plastid, including some with non-photosynthetic functions.
PMID: 25746767 [PubMed – as supplied by publisher]