Mytilin B and MGD2, two antimicrobial peptides of marine mussels: gene structure and expression analysis

Previous research has shown that mytilins and MGDs are two types of 4-kDa, cysteine-rich, cationic antimicrobial peptides, which are abundant in hemoc ytes of the mussels, Mytilus galloprovincialis and M. edulis. The expressio n of the genes encoding these peptides has been analyzed in the hemocytes o f animals subjected to various stress factors, as well as during larval dev elopment. Variations in gene expression in adult mussels have been tested u nder conditions of physical stress, bacterial challenge and heat shock. The results suggest that in adult mussels. the MGD2 gene may be over-expressed with physical and temperature stress, but that reduced expression occurs w ith bacterial challenge. Gene expression during development has been analyz ed using different larval and post-larval stages, ranging from 4-day-old ve liger larvae to 32-day-old post-larvae. The results show that the expressio n of both mytilin B and MGD2 is developmentally regulated, but neither gene is expressed in mussels until after larval settlement and metamorphosis. F inally, the genes encoding two isoforms of these peptides have been cloned and sequenced, revealing that both genes contain four exons and three intro ns. (C) 2000 Elsevier Science Ltd. All rights reserved.