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LmCht5-1 promotes pro-nymphal molting during locust embryonic development

Zhang, Tingting, Liu, Weiwei, Li, Daqi, Gao, Lu, Ma, Enbo, Zhu, Kun Yan, Moussian, Bernard, Li, Sheng, Zhang, Jianzhen
Insect biochemistry and molecular biology 2018 v.101 pp. 124-130
Locusta migratoria, apolysis, chitin, chitinase, embryogenesis, hatching, histology, insects, nymphs
Chitinases, key enzymes involved in degradation of chitin, have been repeatedly shown to play an indispensable role during insect post-embryonic molting processes at stage transitions. However, how chitinases affect insect embryonic development remains to be analyzed. In this study, we investigated the role of chitinase 5–1 (LmCht5-1) during embryonic development of the hemimetabolous insect Locusta migratoria. LmCht5-1 transcript levels were high in pro-nymphs during late embryogenesis. The respective protein localized to both the pro-nymphal and, to a much lesser extent, the newly formed nymphal cuticle. After injection of double stranded RNA against LmCht5-1 into 8 days old embryos, LmCht5-1 transcripts were strongly reduced. Most of dsLmCht5-1-injected pro-nymphs failed to develop to first-instar nymphs and died at or before hatching. Histological analyzes showed that degradation of the pro-nymph cuticle was blocked in these animals. At the ultra-structural level, we found that LmCht5-1 was needed for the degradation of the lamellar procuticle, while the separation of the procuticle from the epicuticle and epidermis (apolysis) was independent of LmCht5-1 function. Taken together, our results indicate that LmCht5-1 and other yet unknown degrading enzymes act in parallel at distinct positions of the cuticle during molting of the pro-nymph to the first-instar nymph during locust embryogenesis.