Neofunctionalization of a second insulin receptor gene in the wing-dimorphic planthopper, Nilaparvata lugens

Abstract

A single insulin receptor (InR) gene has been identified and extensively studied in model species ranging from nematodes to mice. However, most insects possess additional copies of InR, yet the functional significance, if any, of alternate InRs is unknown. Here, we used the wing-dimorphic brown planthopper (BPH) as a model system to query the role of a second InR copy in insects. NlInR2 resembled the BPH InR homologue (NlInR1) in terms of nymph development and reproduction, but revealed distinct regulatory roles in fuel metabolism, lifespan, and starvation tolerance. Unlike a lethal phenotype derived from NlInR1 null, homozygous NlInR2 null mutants were viable and accelerated DNA replication and cell proliferation in wing cells, thus redirecting short-winged–destined BPHs to develop into long-winged morphs. Additionally, the proper expression of NlInR2 was needed to maintain symmetric vein patterning in wings. Our findings provide the first direct evidence for the regulatory complexity of the two InR paralogues in insects, implying the functionally independent evolution of multiple InRs in invertebrates.

Gene Editing and Genetic Control of Hemipteran Pests: Progress, Challenges and Perspectives

“…Methods for efficient macromolecule delivery are essential to any CRISPR genome-editing system and the delivery strategy can be a substantial technological hurdle preventing deployment in target organisms. While temporally delayed by 3 to 5 years relative to the gene-editing advances in D. melanogaster , mosquitoes, the Lepidoptera, and the Coleoptera, CRISPR/Cas9-editing is now reported for nine species of Hemiptera with a total of 17 different genes being targeted ( Tables 2 – 4 ) ( Xue et al, 2018 ; Kotwica-Rolinska et al, 2019 ; Le Trionnaire et al, 2019 ; Zhao et al, 2019 ; Cagliari et al, 2020 ; Heu et al, 2020 ; Reding and Pick, 2020 ; Klobasa et al, 2021 ; Xue et al, 2021 ; Heu et al, 2022 ; Pacheco et al, 2022 ).…”

“…Two insulin receptor genes ( NlInR1 and NlInR2 ) from N. lugens were targets of CRISPR/Cas9 mutagenesis ( Tables 2 – 4 ) ( Zhao et al, 2019 ; Xue et al, 2021 ). Previous studies showed that RNAi silencing of NlInR1 and NlInR2 controls wing polyphenism (short versus long wings, respectively), which is important for N. lugens dispersal ( Xu et al, 2015 ).…”

“…NlInR1 and NlInR2 mutants have some overlapping but also distinct phenotypes indicating their different roles in growth, development and adaptation to stress. For example, homozygous NlInR1 mutants had an early embryonic lethal phenotype, while homozygous NlInR2 mutants did not ( Zhao et al, 2019 ; Xue et al, 2021 ). Heterozygous NlInR1 mutants grew more slowly, had reduced body mass, shorter wings, and a longer lifespan relative to wild-type control insects.…”

“… Zhao et al (2019) also examined the InR1 -dependent transcriptome changes in the mutant versus wild-type N. lugens revealing that NlInR1 regulates genes associated with numerous cellular processes including: insulin resistance, longevity, phototransduction, cellular metabolism, endocytosis, as well as protein biosynthesis and processing. Null mutants in NlInR2 had different phenotypes than NlInR1 mutants providing the first insights into the distinctive roles of this understudied InR2 receptor in insects ( Xue et al, 2021 ). In contrast to NlInR1 mutants, NlInR2 mutants were not lethal, displayed accelerated cell division and cell proliferation in wings (which gave rise to long wings), had defective vein patterning, prolonged developmental time, and decreased fecundity.…”

“…Therefore, it is possible that a different set of germline promoters will be needed for the hemimetabolous Hemiptera. Based on sequence identity to the germline vasa of D. melanogaster, the Nlvasa gene was identified and its promoter was used to generate NlInR1 and NlInR2 mutants in N. lugens ( Zhao et al, 2019 ; Xue et al, 2021 ). The ∼2-kb vasa promoter is the first RNA polymerase II-dependent putative tissue/cell-specific promoter has been used in the Hemiptera.…”