Chitinase (CHI) of Spodoptera frugiperda affects molting development by regulating the metabolism of chitin and trehalose

Abstract

Chitin is the main component of insect exoskeleton and midgut peritrophic membrane. Insect molting is the result of the balance and coordination of chitin synthesis and degradation in chitin metabolism under the action of hormones. In this study, a 678 bp dsRNA fragment was designed and synthesized according to the known CHI (Chitinase) sequence of Spodoptera frugiperda. It was injected into the larvae to observe the molting and development of S. frugiperda. At the same time, the activities of trehalase and chitinase, the contents of trehalose, chitin and other substances were detected, and the expression of related genes in the chitin synthesis pathway was determined. The results showed that CHI gene was highly expressed at the end of each instar, prepupa and pupal stage before molting; At 12 and 24 h after dsRNA injection of CHI gene of S. frugiperda, the expression of CHI gene decreased significantly, and the chitinase activity decreased significantly from 12 to 48 h. The expression of chitin synthase (CHSB) gene decreased significantly, and the chitin content increased significantly. Some larvae could not molt normally and complete development, leading to certain mortality. Secondly, after RNAi of CHI gene, the content of glucose and glycogen increased first and then decreased, while the content of trehalose decreased significantly or showed a downward trend. The activities of the two types of trehalase and the expression levels of trehalase genes decreased first and then increased, especially the trehalase activities increased significantly at 48 h after dsCHI injection. And trehalose-6-phosphate synthase (TPS), glutamine: fructose-6-phosphate amidotransferase (GFAT), UDP-N-acetylglucosamine pyrophosphorylases (UAP), hexokinase (HK), glucose-6-phosphate isomerase (G6PI) and phosphoacetylglucosamine mutase (PAGM) all decreased significantly at 24 h, and then increased or significantly increased at 48 h. These results indicated that when the expression of chitinase gene of S. frugiperda was inhibited, it affected the degradation of chitin in the old epidermis and the formation of new epidermis, and the content of chitin increased, which led to the failure of larvae to molt normally. Moreover, the chitin synthesis pathway and trehalose metabolism were also regulated. The relevant results provide a theoretical basis for screening target genes and developing green insecticides to control pests by using the chitin metabolism pathway.

Chitinase inhibition induces transcriptional dysregulation altering ecdysteroid-mediated control of Spodoptera frugiperda development

“…Chitinase inhibition results in increased chitin synthesis and higher expression of chitin synthase. 18 Berberine-fed insects showed chitin synthase overexpression, which might be the putative reason for higher chitin content to facilitate chitin remodeling. Increased chitin synthesis was also reflected by the overaccumulation of the chitin precursor, glucosamine-6-phosphate.…”

“…Silencing of chitinase leads to decreased levels of glucose, trehalose, and glycogen. 18 , 27 S. frugiperda chitinase inhibition leads to increased Trehalase expression and reduced trehalose levels, causing decreased expression of Trehalose transporter 1 . In brief, increased trehalose hydrolysis upon chitinase inhibition may fulfill the glucose requirement for chitin synthesis.…”

Gamma-ray irradiation's effects on several biological and biochemical processes of Spodoptera frugiperda (Lepidoptera: Noctuidae)

“…Rendering to a phylogenetic analysis, insect chitinases and chitinase-like proteins can be divided into numerous families, as demonstrated by Arakane and Muthukrishnan [25] . Liu et al [26] mention that when the S. frugiperda chitinase gene's expression was blocked, it affected the breakdown of chitin in the old epidermis and the development of new epidermis, and the concentration of chitin increased, which prevented the larvae from going through a normal moulting process. Between 12 and 48 hours, the chitinase activity and the expression of the CHI gene both drastically decreased.…”

Identification of chitinase genes and roles in the larval–pupal transition of Leptinotarsa decemlineata

“…Insects undergo periodic molting to replace their cuticles to accommodate growth. During each molt cycle, a new cuticle is deposited while the inner part of the chitinous procuticle of the old one degrades 6–8 …”

“…During each molt cycle, a new cuticle is deposited while the inner part of the chitinous procuticle of the old one degrades. [6][7][8] The degradation of chitin is facilitated by a two-component chitinolytic enzyme system, consisting of chitinase and β-N-acetylglucosaminidase. Chitinase hydrolyzes chitin into oligosaccharides, [9][10][11] 11 and β-N-acetylglucosaminidase further degrades the oligomers to monomers.…”