Expression and function of cathepsin B-like proteinase in larval hemocytes of Helicoverpa armigera during metamorphosis

Abstract

Previous work has revealed that Helicoverpa armigera cathepsin B-like proteinase (HCB) is expressed in oocytes as well as fat bodies of pupae and adults. It plays key roles in the degradation of yolk proteins during embryogenesis and the decomposition of adult fat bodies of H. armigera. This study investigated the expression and function of HCB in larval hemocytes during larva-pupa metamorphosis. Results showed that the expression of HCB in hemocytes exhibited developmental stage specificity. No HCB was found in hemocytes from 5th-molting larvae. On the contrary, HCB was highly transcribed in the hemocytes from 6th-48-h larvae. Besides, it was abundantly translated in 6th-96-h larvae (prepupation). HCB is mainly expressed in plasmatocytes and granulocytes at both transcriptional and translational levels. The number of plasmatocytes and granulocytes markedly increased before pupation. In addition, hemocytes distributed in hematopoietic organs at early larval stage, then migrated to midgut and fat bodies that would undergo histolysis at later larval stage. These findings suggested that HCB is expressed in H. armigera larval hemocytes and involved in larva-pupa metamorphosis.