# Distinct Roles of Two UDP-N-Acetylglucosamine Pyrophosphorylase Genes in Chitin Biosynthesis and Molting of Oedaleus asiaticus (Orthoptera: Acrididae)

## TL;DR

This study identifies two genes in grasshoppers that are essential for chitin production and molting, offering a potential target for safer pest control methods.

## Contribution

The study reveals distinct roles of OaUAP1 and OaUAP2 genes in chitin biosynthesis and molting in Oedaleus asiaticus, providing new insights for biological pest control.

## Key findings

- OaUAP1 is primarily expressed in the epidermis, while OaUAP2 is mainly expressed in the fat body.
- Silencing either OaUAP1 or OaUAP2 disrupts molting and leads to nymph death.
- 20-hydroxyecdysone increases UAP gene activity, while validamycin decreases it.

## Abstract

The Asian grasshopper (Oedaleus asiaticus) is a serious pest in dry and semi-dry grasslands of Inner Mongolia, China, where outbreaks destroy crops and pastures, harming farming, animal husbandry, and the environment. Current control depends mostly on chemical pesticides, but these cause insect resistance, pollution, and health risks. This study identified two genes, OaUAP1 and OaUAP2, that help produce chitin, the hard material forming the insect’s outer covering. The genes work in different body parts: OaUAP1 mainly in the epidermis and OaUAP2 in the fat body. Silencing either gene prevented proper molting, causing body shrinkage, cracked shells, and death. A natural molting hormone boosted their activity, while a substance that blocks chitin production reduced it. These results show that the genes have distinct but vital roles in insect growth and molting. The findings offer new knowledge for creating safe, targeted biological insecticides that avoid chemical harm, supporting sustainable pest control and the protection of grasslands and agriculture.

UDP-N-acetylglucosamine pyrophosphorylase (UAP) is an essential enzyme in the insect chitin biosynthesis pathway; however, little is known regarding its molecular functions in Oedaleus asiaticus Bey-Bienko (Orthoptera: Acrididae). Here, two UAP genes, OaUAP1 and OaUAP2, were identified and characterized in O. asiaticus. The effects of exogenous treatments, including the molting hormone 20-hydroxyecdysone (20E) and the chitin biosynthesis inhibitor validamycin (VA), were assessed on chitin synthesis. Sequence analyses have shown that the cDNA and deduced amino acid sequences of O. asiaticus share over 90% identity with UAPs in Locusta migratoria. OaUAP1 and OaUAP2 are widely expressed in many tissues and developmental stages but exhibit different expression patterns: OaUAP1 shows higher expression in the epidermis and fifth-instar nymphs, while OaUAP2 is primarily expressed in the fat body and in the fifth-instar nymphs and adults. The functional analysis of two OaUAPs revealed that OaUAP2 was crucial in molting; moreover, its implication also exists in other biosynthetic processes since nymphs maintained normal growth and development. Both OaUAP expressions were upregulated by 20E and downregulated by VA in the chitin biosynthesis pathway. Our findings provide a vital molecular insight into the chitin biosynthesis pathway of O. asiaticus and lay a solid foundation for developing environmentally safe biological insecticides.