Meeting Abstract

69.6  Friday, Jan. 6  Using fluorescent in situ hybridization (FISH) to localize transferred algal genes in the cells of the sacoglossan sea slug, Elysia chlorotica. SCHWARTZ, J.A.*; CURTIS, N.E.; PIERCE, S.K.; Univ. of South Florida, Tampa; Univ. of South Florida, Tampa; Univ. of South Florida, Tampa jschwart@usf.edu

Although horizontal gene transfer (HGT) between unicellular organisms is a common occurrence in nature, only one example of HGT between multicellular species has been experimentally identified. Elysia chlorotica has one of the longest endosymbiotic relationships with chloroplasts of the heterokont alga, Vaucheria litorea. More than 60 genes of algal origin have been identified in E. chlorotica genomic DNA and/or cDNA. Many of these genes are involved in photosynthesis and its maintenance and likely sustain this long-lived endosymbiosis. Although whole genome sequencing is necessary to identify the full complement of algal genes present in the slug, it is of great interest to localize the transferred genes within the host cell. Using FISH probes made from previously identified native algal sequences and confocal microscopy, we have shown that V. litorea phosphoribulokinase (prk), fucoxanthin chlorophyll a/c binding protein (fcp) and photosystem II extrinsic protein O (PsbO) hybridize with nuclei of colchicine treated E. chlorotica embryos. Furthermore, in preliminary tests, among the 15 chromosome pairs in the E. chlorotica karyotype, FISH labeling of both prk and fcp occurs on the same chromosome. This localization may indicate that larger pieces of DNA rather than individual genes are involved in the transfer mechanism. (Supported by an anonymous donor).