Meeting Abstract

85.1  Thursday, Jan. 7  Chlorophyll synthesis by a sea slug (Elysia chlorotica) PIERCE, S. K.*; CURTIS, N. E.; SCHWARTZ, J. A.; Univ. of South Florida; Univ. of South Florida; Univ. of South Florida pierce@cas.usf.edu

The intracellular chloroplast symbiosis between the sea slug, Elysia chlorotica, and chloroplasts of the chromophytic alga, Vaucheria litorea, is supported by functional, algal nuclear genes that have been transferred into the slug genome and are expressed in the slug cell. Presently, we have found 11 transferred algal nuclear genes in the slug genome, most of which code for proteins involved in photosynthesis, which proceeds almost unabated for months while the symbiotic plastids reside in the animal cytoplasm. Several of these transferred genes code for enzymes in the V. litorea chlorophyll a synthesis pathway. We have located the genes in slug genomic DNA and/or RNA, so they are not only present in the genome, but transcribed as well. In addition, we have discovered that chlorophyll a is synthesized from 5-amino-levulinic acid by the slugs, for as long as 6 months in the absence of any opportunity for chloroplast replacement. Although chlorophyll a is synthesized within the chloroplast and must be continuously produced to sustain photosynthesis, the replenishment of the chlorophyll synthesis pathway enzymes is dependent upon the nuclear genome. Our results clearly show that, inside the slug cell, long term chlorophyll a synthesis is accomplished using transferred algal nuclear genes.