Induction of antimicrobial peptides in infected tissues of larval Heliothis virescens (Lepidoptera: Noctuidae)

Abstract

Effective biological control of destructive heliothine larvae via application of microbial entomopathogens or parasitoids is limited by a robust immune response against infection and parasitization. To better understand the immune response of budworms against microbial entomopathogens, several orthologs of antibacterial response proteins were identified and extracted from a tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae), expressed sequence tag database for study of their upregulation by bacterial infection. Transcript sequences corresponding to precursors of 3 antimicrobial peptides from H. virescens hemolymph (virescein, heliomicin and heliocin) have been identified and their induction by bacterial elicitation analyzed. Further, a gloverin-like antibacterial and an H. virescens ortholog of the Lepidopteran hemocytespecific antibacterial Spod-X-Tox have been identified. Induction of these selected antibacterial protein transcripts by bacterial infection were quantitated using quantitative RT-PCR in hemocytes and fat bodies. Transcript levels of all were elevated by bacterial elicitation in both tissues as early as 3 hours post-treatment.