A nuclear receptor HR4 is essential for the formation of epidermal cuticle in the migratory locust, Locusta migratoria. (April 2022)

• Record Type: Journal Article
• Authors: Liu, Xiaojian; Li, Juan; Sun, Yawen; Liang, Xiaoyu; Zhang, Rui; Zhao, Xiaoming; Zhang, Min; Zhang, Jianzhen
• Is Part Of: Insect biochemistry and molecular biology. Volume 143(2022)
• Publication Date: 2022-04
• Subjects: Locusta migratoria -- Hormone receptor 4 -- 20-hydroxyecdysone -- Cuticle formation -- Chitin synthesis and degradation; Insect biochemistry -- Periodicals; Insects -- Physiology -- Periodicals; Insects -- Molecular aspects -- Periodicals; Biochemistry -- Periodicals; Insectes -- Biochimie -- Périodiques; Insectes -- Composition -- Périodiques; Insectes -- Physiologie -- Périodiques; Insectes -- Aspect moléculaire -- Périodiques; Biochimie -- Périodiques; Biochemistry; Insect biochemistry; Insects -- Molecular aspects; Insects -- Physiology; Periodicals; 572.8157
• DOI: 10.1016/j.ibmb.2022.103740
• Languages: English
• ISSNs: 0965-1748

Abstract

Abstract: Nuclear receptors (NRs) function as key factors in diverse signaling and metabolic pathways. Previous studies have focused on the roles of a nuclear receptor, hormone receptor 4 (HR4), mainly in holometabolous insects, while current knowledge of its function in hemimetabolous insects is still limited. In this study, we identified a HR4 gene in the orthopteran species Locusta migratoria . The full-length open reading frame of LmHR4 comprises 2694-nucleotides encoding a polypeptide of 897 amino acids, which contained a DNA-binding and a ligand-binding domain. Analyzing LmHR4 expression by quantitative reverse-transcription PCR (RT-qPCR) revealed that LmHR4 was highly expressed in integument, hindgut and fat body. During development from 3rd and 5th nymphal instars, the expression of LmHR4 reached maximal levels before ecdysis. We further demonstrated that LmHR4 expression is induced by 20-hydroxyecdysone (20E) and suppressed by silencing LmEcR, suggesting that LmHR4 expression is controlled by 20E signaling. The ds LmHR4 -injected nymphs failed to molt and remained in the nymphal stage until death. Hematoxylin and eosin staining of the integument indicated that apolysis in the ds LmHR4 -injected insects was delayed compared to that in control insects. Chitin staining and ultra-structural analysis showed that both the synthesis of the new cuticle and the degradation of the old cuticle were blocked in ds LmHR4 -injected insects. Silencing LmHR4 decreased 20E titer and down-regulated the transcript levels of genes involved in chitin synthesis and degradation. Taken together, these results suggest that LmHR4 is essential for the formation of epidermal cuticle by mediating the 20E signaling to regulate the expression of chitin synthesis and degradation genes. Graphical abstract: Image 1 Highlights: The expression of LmHR4 is induced by 20E through LmEcR. Nymphs injected with ds LmHR4 failed to molt. LmHR4 silencing blocks the synthesis of new cuticle and degradation of old cuticle. Knockdown of LmHR4 results in decreased 20E titer. LmHR4 regulates genes involved in chitin synthesis and degradation.