Chitin metabolism as a potential target for RNAi‐based control of the forestry pest Hyblaea pueraCramer (Lepidoptera: Hyblaeidae)

Abstract

BACKGROUND Hyblaea puera, commonly known as the teak defoliator, is a serious pest in teak plantations. Despite the availability of control measures, this pest causes losses in yield and quality of timber through voracious feeding. RNA interference (RNAi) is a promising strategy for the control of this pest. Chitin metabolism, which is vital for the growth and development of arthropods, is a potential target for developing RNAi‐based insecticides. RESULTS To assess the effects of chitin metabolism inhibition, H. puera larvae were treated with a chitin synthesis inhibitor, diflubenzuron (DFB). DFB treatment caused pupal deformities and disrupted eclosion. Partial gene sequences for three key genes of H. puera chitin metabolism were cloned and sequenced: chitin synthase 1 (HpCHS1), chitinase‐h (HpChi‐h) and ecdysone receptor (HpEcR). Feeding dsRNA cognate for these three target genes to the first instar of H. puera resulted in mortality and reduction in the corresponding transcript levels as assessed through qRT‐PCR. This is the first report of RNAi in this forestry pest. The highest mortality was 45.9%, in response to dsHpEcR treatment; HpChi‐h transcripts were the most down‐regulated in response to dsHpEcR feeding. DsHpEcR RNAi resulted in growth inhibition and molting arrest. The mortalities were 29.7% and 32.4% for dsHpCHS1 and dsHpChi‐h feeding, respectively. CONCLUSION Chitin metabolism could be a potential target for RNAi‐based control of H. puera, and HpCHS1, HpChi‐h and HpEcR could be suitable target genes. However, the RNAi efficacy needs to be improved through formulations that improve stability and uptake, and employing better delivery strategies. © 2021 Society of Chemical Industry.

Group h Chitinase: A Molecular Target for the Development of Lepidopteran-Specific Insecticides

“…The survival rates after injection of dsChi-h in the pupal and adult stages were 72.38 and 48.52%, respectively. The effect of RNAi on Chi-h in Hyblaea puera was also assessed; the mortality on day 4 after the treatment was 32.4% …”

“…The effect of RNAi on Chi-h in Hyblaea puera was also assessed; the mortality on day 4 after the treatment was 32.4%. 22 ■ CRYSTAL STRUCTURE OF OF CHI-H Of Chi-h from O. furnacalis is the only Chi-h with a known crystal structure. 19 Of Chi-h adopts a compact and elongated structure (Figure 3A).…”

“…ChtI, ChtII, and Chi-h are involved in the degradation of the cuticle and peritrophic matrix chitin . ChtIII is proposed to be involved in processing nascent chitin chains into higher order structures during cuticle assembly and organization. − ChtIV may play a role in the degradation of chitin, defense against fungi, and immunity against gut infections. − Group V chitinases [imaginal disc growth factors (IDGFs)] have been shown to regulate tissue remodeling and cell proliferation in insects. ,, Most chitinase families are distributed in all insects, with the exception of group h chitinase (Chi-h), which has been found only in Lepidoptera (the order including butterflies and moths); Lepidoptera includes the largest number of insect pests that threaten crops. − Chi-h is one of the key enzymes in the chitinolytic system of Lepidoptera, and silencing the Chi-h-encoding gene led to the death of the insects. ,− Moreover, the structure of Chi-h is significantly different from that of human and other insect chitinases. ,− This evidence suggests that Chi-h is an ideal target for the development of lepidopteran-specific insecticides. This minireview focuses on the latest progress in research into Chi-h, including its biological function, crystal structure, and small molecular inhibitors of the enzyme.…”

Assessment of Sesamia nonagrioides (Lepidoptera: Noctuidae) EcR and USP Genes as Targets for Exogenous Non-Persistent RNAi

“…Because of the tremendous physiological and molecular effects of EcR and USP in the developmental processes of insects, both genes have attracted great attention in RNAi research as potential targets in the development of RNAi-based insecticides. Targeting these genes caused extended lethality and developmental malformations to many insects like in the Lepidopterans Hyblaea puera Cramer (Lepidoptera: Hyblaeidae) [25] and Spodoptera exigua [26], in the grain Aphid (Sitobion avenae F.) [27], in the Coleopteron Leptinotarsa decemlineata [28,29], in honey bees [30], in the cockroach Diploptera puncata, etc. [31].…”