CHARACTERIZATION OF THE SAXITOXIN BIOSYNTHETIC STARTING GENE, sxtA, IN THE TOXIC DINOFLAGELLATE, Pyrodinium bahamense var. compressum

Abstract

Pyrodinium bahamense var. compressum, a saxitoxin-producing dinoflagellate, frequently blooms on the west coast of Sabah. According to previous studies, saxitoxin from cyanobacteria and dinoflagellates is manufactured from similar precursors (three arginines, one methionine via S-adenosylmethionine and one acetate) through identical biochemical pathways. The saxitoxin biosynthetic starting gene, sxtA is essential for synthesizing the final compound. The genes associated with saxitoxin synthesis in Alexandrium spp. and cyanobacteria have been previously identified; in spite of this, limited information is known about P. bahamense var. compressum, the principal tropical saxitoxin-producing dinoflagellate. In this study, the exclusive starting gene for saxitoxin biosynthesis, sxtA, specifically the SAM-dependent methyltransferase, sxtA1 and the class II aminotransferase coding gene, sxtA4 of P. bahamense was studied. Comparative sequence analysis revealed that sxtA1 and sxtA4 genes in P. bahamense exhibited high sequence similarity with other toxic dinoflagellates such as Alexandrium fundyense and Alexandrium tamarense. This study provides a genetic insight into saxitoxin biosynthesis in P. bahamense, which will be helpful in future investigations such as the development of genetic markers to study the expression of the sxtA gene and the identification of potential molecular targets for bloom characterization.