Using Algal Transcriptome Sequences to Identify Transferred Genes in the Sea Slug, Elysia chlorotica

The first molecular evidence of horizontal gene transfer between multicellular eukaryotes was our discovery of the presence of three Vaucheria litorea nuclear-encoded genes [fucoxanthin chlorophyll a/c-binding protein (fcp) and light-harvesting complex 1 and 2 (Lhcv1 and 2)] in the genomic DNA of the sea slug, Elysia chlorotica, which are used to support the chloroplast endosymbiosis in the slug. These genes are translated and transcribed in the host cell, and vertically transmitted to subsequent generations of the host species. In order to provide a database of native V. litorea sequences to facilitate the search for additional transferred genes between these two species, we have partially sequenced and annotated the transcriptome of V. litorea, using 454 Life Science's next generation pyrosequencing technology. Preliminary analysis of the sequence data has led to the discovery of six additional algal nuclear genes in E. chlorotica cDNA and genomic DNA, which encode enzymes in the chlorophyll synthesis pathway as well as additional light-harvesting and metabolic enzymes. Furthermore, we confirm the recent discovery of the Calvin-Benson cycle gene, prk.