Phenoloxidase in larvae ofPlodia interpunctella (Lepidoptera: Pyralidae): Molecular cloning of the proenzyme cDNA and enzyme activity in larvae paralyzed and parasitized byHabrobracon hebetor (Hymenoptera: Braconidae)

Abstract

Phenoloxidase (PO) is a major component of the insect immune system. The enzyme is involved in encapsulation and melanization processes as well as wound healing and cuticle sclerotization. PO is present as an inactive proenzyme, prophenoloxidase (PPO), which is activated via a protease cascade. In this study, we have cloned a full-length PPO1 cDNA and a partial PPO2 cDNA from the Indianmeal moth, Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae) and documented changes in PO activity in larvae paralyzed and parasitized by the ectoparasitoid Habrobracon hebetor (Say) (Hymenoptera: Braconidae). The cDNA for PPO1 is 2,748 bp and encodes a protein of 681 amino acids with a calculated molecular weight of 78,328 and pI of 6.41 containing a conserved proteolytic cleavage site found in other PPOs. P. interpunctella PPO1 ranges from 71-78% identical to other known lepidopteran PPO-1 sequences. Percent identity decreases as comparisons are made to PPO-1 of more divergent species in the orders Diptera (Aa-48; As-49; and Sb-60%) and Coleoptera (Tm-58; Hd-50%). Paralyzation of host larvae of P. interpunctella by the idiobiont H. hebetor results in an increase in phenoloxidase activity in host hemolymph, a process that may protect the host from microbial infection during self-provisioning by this wasp. Subsequent parasitization by H. hebetor larvae causes a decrease in hemolymph PO activity, which suggests that the larval parasitoid may be secreting an immunosuppressant into the host larva during feeding.

A Genome-Wide Survey for Host Response of Silkworm, Bombyx mori during Pathogen Bacillus bombyseptieus Infection

“…Melanin formation in the hemolymph is caused by the serine protease cascade melanization pathway after pathogen infection [89]–[91]. After Bb oral infection has induced an immune response, the serine protease cascade melanization pathway was activated.…”

Linkage map of the peppered moth, Biston betularia (Lepidoptera, Geometridae): a model of industrial melanism

“…Genes were obtained primarily as mRNA-coding sequences either from a transcriptome library ( Van't Hof and Saccheri, 2010) or with gene-specific degenerate primers using complementary DNA or genomic DNA as template following the methods described in Van't Hof and Saccheri (2010). All primers were designed specifically for this project, with the exception of Ddc and Pgi degenerate primers (Regier, 2007) and PpoI_F (Hartzer et al, 2005); the primer sequences are included in Supplementary Table S2. Several gene sequences were characterized from BACs that were isolated with PCR probes derived from mapped and sequenced AFLPs.…”

Effects of Inhibitors on Haemolymph Phenoloxidase From Rosaceous Branch Borer, Ospheranteria Coerulescens (Coleoptera: Cerambycidae)

“…Due to the importance of this enzyme in insect immunity, it was characterized in some insects such as the tobacco budworm, Musca domestica, Drosophila melanogaster, Aedes aegypti, Plodia interpunctella, and Sarcophaga bullata (Yamaura et al 1980;Ourth 1988;Fujimoto et al 1993;Burks and Fuchs 1995;Chase et al 2000;Wang et al 2004;Hartzer et al 2005). The study of this enzyme's properties is necessary not only for comparative study but also to understand the physiology of coleopteran immunity.…”