Identification and Functional Characterization of Two Chitin Synthases in the Black Cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae)

Abstract

The black cutworm, Agrotis ipsilon (Hufnagel), a seasonal migrant and a prolific generalist, can feed on nearly all vegetables and grain crops, causing considerable economic impacts on a global scale. Given its cryptic nature, A. ipsilon management has been extremely challenging. Chitin synthase (CHS), a key enzyme involved in chitin biosynthetic pathway and crucially important for the growth and development of insects, is the molecular target of chitin synthesis inhibitors, a group of broad-spectrum insecticides that is compatible with Integrated Pest Management practices. In this study, we investigated the potential of targeting chitin synthases to control A. ipsilon. As a result, two chitin synthases, AiCHS1 and AiCHS2, were identified and cloned from A. ipsilon. The temporal-spatial distribution study showed that AiCHS1 was predominantly expressed at the pupal stage and most abundant among tissues of head capsule and integument, while AiCHS2 was mainly expressed at the sixth instar larval stage and tissues of foregut and midgut. RNAi-based functional study confirmed gene silencing caused significant reduction in the expression levels of the corresponding mRNA, as well as resulted in abnormal pupation and mortality, respectively. Furthermore, under the treatment of lufenuron, a chitin synthesis inhibitor, A. ipsilon responded with an elevated expression in AiCHS1 and AiCHS2, while larvae showed difficulty in shedding old cuticle, and a cumulative mortality of 69.24% at 48 h. In summary, chitin synthases are crucial for chitin biosynthesis in A. ipsilon and can be targeted for the control (e.g., RNAi-based biopesticides) of this devastating insect pest.

Unclassified glutathione‐S‐transferase AiGSTu1 confers chlorantraniliprole tolerance in Agrotis ipsilon

“…60 Silencing of chitin synthase and chitinase genes in A. ipsilon was successfully conducted by injection of dsRNA, and knockdown of these genes induced high larval mortality. 61,62 We performed RNAi analysis to evaluate the role of AiGSTu1 in the detoxification of CAP. The results showed that dsAiGSTu1 injection significantly reduced the expression level of AiGSTu1.…”

“…RNAi is a post‐transcriptional gene silencing process and a powerful tool for studying the functions of genes by suppressing gene expression 60 . Silencing of chitin synthase and chitinase genes in A. ipsilon was successfully conducted by injection of dsRNA, and knockdown of these genes induced high larval mortality 61,62 . We performed RNAi analysis to evaluate the role of AiGSTu1 in the detoxification of CAP.…”

Validamycin Inhibits the Synthesis and Metabolism of Trehalose and Chitin in the Oriental Fruit Fly, Bactrocera dorsalis (Hendel)

“…Chitin is the main component of the cuticle and peritrophic membranes of insects [ 10 , 11 , 12 , 13 , 14 ], and the disruption of the chitin metabolism has a lethal effect on insects [ 15 , 16 , 17 , 18 , 19 ]. For example, the silencing a chitin synthase of Spodoptera frugiperda (Lepidoptera: Noctuidae) that is highly expressed in the cuticle caused a high rate of larval mortality and pupal malformation [ 20 ].…”