Chlorophyll a synthesis by an animal using transferred algal nuclear genes
Chlorophyll synthesis is an ongoing requirement for photosynthesis and a ubiquitous, diagnostic characteristic of plants and algae amongst eukaryotes. However, we have discovered that chlorophyll a (Chla) is synthesized in the symbiotic chloroplasts of the sea slug, Elysia chlorotica, for at least 6 months after the slugs have been deprived of the algal source of the plastids, Vaucheria litorea. In addition, using transcriptome analysis and PCR with genomic DNA, we found 4 expressed genes for nuclear-encoded enzymes of the Chla synthesis pathway that have been horizontally transferred from the alga to the genomic DNA of the sea slug. These findings demonstrate the first discovery of Chla production in an animal using transferred nuclear genes from its algal food.