NPC1b as a novel target in controlling the cotton bollworm, Helicoverpa armigera

Abstract

BACKGROUND: Insects cannot synthesize sterols and must acquire them from food. The mechanisms underlying how insects uptake dietary sterols are largely unknown except that NPC1b, an integral membrane protein, has been shown to be responsible for dietary cholesterol uptake in Drosophila melanogaster. However, whether NPC1b orthologs in other insect species, particularly the economically important pests, function similarly remains to be determined. RESULTS:In this study, we characterized the function of NPC1b in Helicoverpa armigera, a global pest that causes severe yield losses to many important crops. Limiting dietary cholesterol uptake to insects significantly inhibited food ingestion and weight gain. Compared to the wild-type H. armigera, the CRISPR/Cas9-edited NPC1b mutant larvae were incapable of getting adequate cholesterol and died in their early life stage. Gene expression profile and in situ hybridization analyses indicated that NPC1b was mainly expressed in the midgut where dietary cholesterol was absorbed. Expression of NPC1b was also correlated with the feeding life stages and was especially upregulated during early larval instars. Protein-ligand docking and sequence similarity analyses further demonstrated that NPC1b proteins of lepidopteran insects shared a relatively conserved cholesterol binding region, NPC1b_NTD, which, however, was highly divergent from bees-derived sequences.CONCLUSION: NPC1b was crucial for dietary cholesterol uptake and growth of H. armigera, and therefore could serve as an insecticide target for the development of a novel pest-management approach to control this economically significant insect pest with little off-target effect on bees and sterol-autotrophic animals.

Post-feeding transcriptomics reveals essential genes expressed in the midgut of the desert locust

“…SgNPC1b shows a midgut and associated caeca specific expression ( Figure 5A ), similar to SgVAHa1 , implying a specialized function of SgNPC1b in the midgut, which is consistent with findings in the holometabolan species, D. melanogaster , H. armigera, T. castaneum and Tenebrio molitor ( Voght et al, 2007 ; Oppert et al, 2018 ; Zheng et al, 2020 ). In line with these reports, we found two NPC1-like sequences in T. castaneum in the BeetleAtlas 9 database ( Naseem et al, 2023 ), one putative NPC1a sequence (TC005088) with uniform distribution and one putative NPC1b sequence (TC033918) with midgut-specific expression.…”

“…Due to gene duplication, the majority of insects possess two NPC1 homologues, namely, NPC1a and NPC1b ( Zheng et al, 2018 ). NPC1b was shown to be crucial for dietary sterol absorption in the midgut of D. melanogaster and H. armigera ( Voght et al, 2007 ; Zheng et al, 2020 ). After absorption, sterols are taken up in the lysosomes and are transferred by NPC2 to NPC1a which is integrated in the lysosomal membrane ( Jing and Behmer, 2020 ).…”

Functional analysis of a NPC1 gene from the whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae)

“…Results showed that cholesterol feeding did induce the expression of BtNPC1, supporting its role in sterol absorption. Similarly, in Helicoverpa armigera, the expression of NPC1b was induced after diet injection or cholesterol uptake (Zheng et al, 2020). To date, it seems excessive cholesterol may have adverse effect on BtNPC1…”

CRISPR/Cas9 for Insect Pests Management: A Comprehensive Review of Advances and Applications

“…Thus, NPC1b can be a potential target for pest management. However, the technique might have some off-target effects [72]. Wang et al used the CRISPR/Cas9 system in H. armigera and proved that Cry1Ac resistance relies on HaCad (which is also a key receptor of Cry1Ac).…”