A cathepsin L‐like proteinase is involved in moulting and metamorphosis in Helicoverpa armigera

Abstract

Holometabolous insects undergo larval moulting and metamorphosis within their life cycle. A cDNA encoding the cathepsin L-like proteinase Ha-cathL has been cloned from Helicoverpa armigera. It has a sequence of 1826 bp and encodes a 550-residue protein with a molecular mass of 63 kDa. Northern blot analysis indicated that Ha-cathL is specifically expressed in haemocytes, with increased expression during larval moulting and metamorphosis. In vivo experimentation revealed that Ha-cathL is up-regulated by 20-hydroxyecdysone. Meanwhile, in situ hybridization and immunocytochemistry revealed that Ha-cathL mRNA is mainly expressed in granulocytes and plasmatocytes. Knock down of cathepsin L by RNA interference results in larvae death before pupation or the formation of a chimeric pupa containing a larval head and thorax, abnormal wings and the pupal abdomen. The reason for this is that the affected haemocytes cannot become granulated, and therefore cannot participate in fat body remodelling and wing development. These facts suggest that Ha-cathL is involved in larval moulting and metamorphosis by participating in the functioning of haemocytes.

Crystal structure of Bombyx mori arylphorins reveals a 3:3 heterohexamer with multiple papain cleavage sites

“…Our data showed that most silkworm papain-like cysteine proteases genes are highly expressed in metamorphosis not only in wandering stage involving in molting and metamorphosis 17,18 but also in later pupa stage and adult cuticle formation stage, which are highly correlated to the digestion time scale of B. mori arylphorin in vivo [ Fig. 5(D)].…”

Diet-delivered RNAi in Helicoverpa armigera – Progresses and challenges

“…RNAi mediated by dsRNA ingestion requires higher dosage and multiple administrations until the onset of silencing in insects when compared to RNAi via injection in the haemolymph (Chen et al, 2008;Tian et al, 2009;Zhu et al, 2011), although dosages needed to elicit effect via injection in H. armigera remain measured in micrograms (Bober and Rafaeli, 2010;Cai et al, 2014;Du et al, 2012;Hou et al, 2012;Qiao et al, 2014;Sivakumar et al, 2007;Tang et al, 2012;Wang et al, 2010;Yang and Han, 2014a).…”

Cathepsins of lepidopteran insects: Aspects and prospects

“…Substantial evidences in this direction are provided by the RNAi interference experiments on various cathepsin genes. On silencing CathL, a marked developmental as well as phenotypic deformation was observed like mortality prior to pupation and occurrence of chimeric H. armigera pupae (with larval head and pupal abdomen) (Wang et al, 2010). Similarly, in B. mori, inhibition of larva-pupa transition was seen on silencing of CathB (Wang et al, 2008); and delayed or abnormal pupation in the case when CathD genes were suppressed (Gui et al, 2006).…”

“…Programmed cell death (PCD) of the fat body cells during metamorphosis in H. armigera is dependent on CathL. In CathL silenced lines, the expression of apoptosis effector gene caspase-1 decreased while the apoptosis inhibitor gene survivin was upregulated, suggesting that Ha-CathL regulates the apoptotic process in the fat body cells (Wang et al, 2010). Hemocyte specific expression of CathL explains that it might be involved in the autophagy of degraded fat body cells from the hemolymph since it is significantly active in the granulocytes and plasmatocytes, which are the main phagocytic cells (Wang et al, 2010;Wood and Jacinto, 2007).…”

“…Representations were prepared by using DOG: Domain graph tool v2.0 (Ren et al, 2009). role in the proteolytic dissociation and release of fat body cells into the hemolymph. In hemolymph, the relatively lower activity of Har-CL was compensated by a different and unrelated form of CathL (HaCathL), which is highly expressed in the granulocytes (Wang et al, 2010). HaCathL is responsible for conversion of granulocytes into macrogranulocytes during larva-pupa metamorphosis.…”