Crucial roles of specialized chitinases in elytral and hindwing cuticles construction in Leptinotarsa decemlineata

The Colorado potato beetle (CPB), Leptinotarsa decemlineata, is a major potato (Solanum tuberosum) pest, infesting over 16 million km² and causing substantial economic losses. The insect cuticle forms an apical extracellular matrix (ECM) envelope covering exposed organs to direct morphogenesis and confer structural protection. While select chitinase (Cht) genes have proven essential for larval development, their potential activities directing ECM remodeling underlying adult wing maturation remain undefined.

We investigated the expression patterns and performed an oral RNA interference (RNAi) screen targeting 19 LdChts in late-instar L. decemlineata larvae. Subsequently, we assessed their effects on adult eclosion and wing characteristics. Knockdown of LdCht5, LdCht7, LdCht10, LdIDGF2, and LdIDGF4, as well as others from Group IV (LdCht15, LdCht12, LdCht17, and LdCht13) and Groups VII-X (LdCht2, LdCht11, LdCht1, and LdCht3), resulting in shrunken, misshapen elytra with reduced areal density, as well as transverse wrinkling and impaired wing-tip folding in hindwings. Scanning electron micrographs revealed eroded elytral ridges alongside thinned, ruptured hindwing veins, indicative of mechanical fragility post-LdCht suppression. Spectroscopic analysis uncovered biomolecular alterations underlying the elytral anomalies, including decreases in peaks representing chitin, proteins, and lipids. This loss of essential ECM components provides evidence for the fragility, wrinkling, and shrinkage observed in the RNAi groups.

Our findings elucidate the crucial role of chitinases in the turnover of chitinous cuticles on beetle wings, offering insights into RNAi-based control strategies against this invasive pest. © 2024 Society of Chemical Industry.