Identification and functional analysis of three defensin-related antimicrobial peptides genes from Manduca sexta

Insects have an array of strategies to defend themselves against attacks by bacteria, fungi, parasites, and viruses. Antimicrobial peptides play very important roles in the innate immune system of insects that rely solely on innate responses to combat a wide array of pathogens. Here we report identification of three defensin-related antimicrobial peptides genes (Def 1, Def 2 and Def 3) from the tobacco hornworm, Manduca sexta. qRT-PCR results revealed that Def 1, Def 2 and Def 3  mRNA  are detected in hemocytes, fat body, epidermis, testis and malpighian tubule of naïve larvae. The mRNA levels of Def 1, Def 2 and Def 3 increased significantly in larval hemocytes and fat body after injection of Escherichia coli and Staphylococcus aureus.