Insect group II chitinase OfChtII promotes chitin degradation during larva-pupa molting

The insect group II chitinase (ChtII, also known as Cht10) is a unique chitinase with multiple catalytic and chitin binding domains. It has been proved to be an essential chitinase for molting genetically. However, ChtII's role in chitin degradation during insect development remains poorly understood. Obtaining this knowledge is the key to fully understanding the chitin degradation system in insect. Here, we investigated the role of OfChtII during the molting of Ostrinia furnacalis, a model lepidopteran pest insect. OfChtII was expressed earlier than OfChtI (OfCht5) and OfChi-h, at both the gene and protein levels during larva-pupa molting as evidenced by qPCR and western blot analyses. A truncated OfChtII, OfChtII-B4C1, was recombinantly expressed in Pichia pastoris cells and purified to homogeneous. The recombinant OfChtII-B4C1 loosened compacted chitin particles and produced holes in the cuticle surface as evidenced by scanning electron microscopy. It synergized with OfChtI and OfChi-h when hydrolyzing insoluble α-chitin. These findings suggested an important role for ChtII during insect molting and also provided a strategy for the coordinated degradation of the cuticular chitin during insect molting by ChtII, ChtI and Chi-h. This article is protected by copyright. All rights reserved.