Diversity in the Genomic Organization and Regulation of the Penaeidin Genes in Litopenaeus vannamei

Nuala O’Leary^1,2 and Paul S. Gross^1,2

^1. Marine Biomedicine and Environmental Sciences Center, Medical University of South Carolina, Charleston, SC

² Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC

The Pacific White Shrimp, Litopenaeus vannamei, is an essential species for commercial shrimp aquaculture. However, diseases brought on by bacterial, fungal and viral infections have resulted in significant economics losses and increasingly threaten the long-term sustainability of the shrimp aquaculture industry. The secretion of antimicrobial peptides (AMPs) is an essential component of the innate immune systems of most organisms.  In the penaeid shrimp members of the penaeidin family of AMPs share a unique two-domain structure consisting of proline and cysteine-rich regions. Three distinct members (classes-2, -3 and -4) of the penaeidin gene family are expressed in Litopenaeus vannamei.  One of the most striking characteristics of the penaeidins is the presence of a highly conserved leader sequence that is nearly 100% conserved across class both within and between species, whereas the two active domains are only 40% similar.  Adding to their complexity each penaeidin class displays a significant degree of isoform diversity.  The focus of our research is to better understand the functional significance of penaeidin diversity as well as the mechanisms by which diversity is generated.  We show that each of the penaeidin classes is encoded by separate genes and are expressed at dramatically different levels in normal hemocytes.  We have isolated upstream promoters of each of these genes and identified potential cis-regulatory motifs within these regions. In addition we have shown that these promoters each of these genes and have shown that these regions can drive transcription in a heterologous cell culture system.