Chitin Synthases Are Critical for Reproduction, Molting, and Digestion in the Salmon Louse (Lepeophtheirus salmonis)

Abstract

Chitin synthase (CHS) is a large transmembrane enzyme that polymerizes Uridine diphosphate N-acetylglucosamine into chitin. The genomes of insects often encode two chitin synthases, CHS1 and CHS2. Their functional roles have been investigated in several insects: CHS1 is mainly responsible for synthesizing chitin in the cuticle and CHS2 in the midgut. Lepeophtheirus salmonis is an ectoparasitic copepod on salmonid fish, which causes significant economic losses in aquaculture. In the present study, the tissue-specific localization, expression, and functional role of L. salmonis chitin synthases, LsCHS1 and LsCHS2, were investigated. The expressions of LsCHS1 and LsCHS2 were found in oocytes, ovaries, intestine, and integument. Wheat germ agglutinin (WGA) chitin staining signals were detected in ovaries, oocytes, intestine, cuticle, and intestine in adult female L. salmonis. The functional roles of the LsCHSs were investigated using RNA interference (RNAi) to silence the expression of LsCHS1 and LsCHS2. Knockdown of LsCHS1 in pre-adult I lice resulted in lethal phenotypes with cuticle deformation and deformation of ovaries and oocytes in adult lice. RNAi knockdown of LsCHS2 in adult female L. salmonis affected digestion, damaged the gut microvilli, reduced muscular tissues around the gut, and affected offspring. The results demonstrate that both LsCHS1 and LsCHS2 are important for the survival and reproduction in L. salmonis.

First Insights about Antiparasitic and Action Mechanisms of the Antimicrobial Peptide Hepcidin from Salmonids against Caligus rogercresseyi

“…These structures possibly separate from the parasite, potentially giving rise to new polymers shaping the subsequent copepodite stage. Chitin is present in the peritrophic matrix of these ectoparasites, covering the microvilli of their intestines [ 51 ], suggesting that effects on chitin could induce morphological changes in the intestine, influencing feeding behavior [ 52 ].…”

Potential inhibitory effects of compounds ZK-PI-5 and ZK-PI-9 on trehalose and chitin metabolism in Spodoptera frugiperda (J. E. Smith)

“…Interfering with LmCHS2 transcription of Locusta migratoria reduced midgut chitin synthesis, resulting in high mortality of the insect ( Liu et al, 2012 ). The above studies have showed that changes in CHS gene expression led to the obstruction of insect development, deformity, molting difficulty, and even death, thereby affecting insect growth and development ( Roach et al, 2012 ; Tang et al, 2012 ; Contreras et al, 2016 ; Harðardóttir et al, 2021 ). We confirmed that ZK-PI-5 could directly reduce membrane-bound trehalase activity, and downregulate the expression level of SfTRE2 and SfCHS2 , lead to chitin metabolism disorder, affect chitin content and the growth and development of S. frugiperda , and lead to abnormal development and even death of S. frugiperda ( Figure 7B ).…”

RNA Interference-Mediated Suppression of Ecdysone Signaling Inhibits Choriogenesis in two Coleoptera species

“…Moreover, dietary introduction of chitin synthesis inhibitors declines fecundity in A. aegypti [13]. In addition, RNAi of LsChS1 in pre-adult I results in deformation of ovaries and oocytes in adult Lepeophtheirus salmonis [40]. This result suggests the likelihood that CLS may also be present in eggshells and deficiency of CLS causes misshapen eggs in other arthropods.…”