ORCID Profile
0000-0001-6875-0252
Current Organisation
Peter MacCallum Cancer Centre
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Publisher: Springer Science and Business Media LLC
Date: 18-03-2019
DOI: 10.1038/S41559-019-0837-Y
Abstract: Imidacloprid, the world's most used insecticide, has caused considerable controversy due to harmful effects on non-pest species and increasing evidence showing that insecticides have become the primary selective force in many insect species. The genetic response to insecticides is heterogeneous across populations and environments, leading to more complex patterns of genetic variation than previously thought. This motivated the investigation of imidacloprid resistance at different temperatures in natural populations of Drosophila melanogaster originating from four climate extremes replicated across two continents. Population and quantitative genomic analysis, supported by functional tests, have revealed a mixed genetic architecture to resistance involving major genes (Paramyosin and Nicotinic-Acetylcholine Receptor Alpha 3) and polygenes with a major trade-off with thermotolerance. Reduced genetic differentiation at resistance-associated loci indicated enhanced gene flow at these loci. Resistance alleles showed stronger evidence of positive selection in temperate populations compared to tropical populations in which chromosomal inversions In(2 L)t, In(3 R)Mo and In(3 R)Payne harbour susceptibility alleles. Polygenic architecture and ecological factors should be considered when developing sustainable management strategies for both pest and beneficial insects.
Publisher: Elsevier BV
Date: 04-2021
Publisher: Elsevier BV
Date: 12-2021
DOI: 10.1016/J.IBMB.2021.103652
Abstract: Under exposure to harmful environmental stresses, organisms exhibit a general stress response involving upregulation of the expression of heat shock proteins (HSPs) which is thought to be adaptive. Small heat shock proteins (sHSPs) are key components of this response, although shsp genes may have other essential roles in development. However, the upregulation of expression of a suite of genes under stress may not necessarily be evidence of an adaptive response to stress that involves those genes. To explore this issue, we used the CRISPR/Cas9 system to investigate pleiotropic effects of the hsp23 gene in Drosophila melanogaster. Transgenic flies carrying a pCFD5 plasmid containing sgRNAs were created to generate a complete knockout of the hsp23 gene. The transgenic line lacking hsp23 showed an increased hatch rate and no major fitness costs under an intermediate temperature used for culturing the flies. In addition, hsp23 knockout affected tolerance to hot and cold temperature extremes but in opposing directions knockout flies had reduced tolerance to cold, but increased tolerance to heat. Despite this, hsp23 expression (in wild type flies) was increased under both hot and cold conditions. The hsp23 gene was required for heat hardening at the pupal stage, but not at the 1st-instar larval stage, even though the gene was upregulated in wild type controls at that life stage. The phenotypic effects of hsp23 were not compensated for by expression changes in other shsps. Our study shows that the fitness consequences of an hsp gene knockout depends on environmental conditions, with potential fitness benefits of gene loss even under conditions when the gene is normally upregulated.
Publisher: Oxford University Press (OUP)
Date: 13-07-2021
Abstract: Cholinergic signaling dominates the insect central nervous system, contributing to numerous fundamental pathways and behavioral circuits. However, we are only just beginning to uncover the erse roles different cholinergic receptors may play. Historically, insect nicotinic acetylcholine receptors have received attention due to several subunits being key insecticide targets. More recently, there has been a focus on teasing apart the roles of these receptors, and their constituent subunits, in native signaling pathways. In this study, we use CRISPR-Cas9 genome editing to generate germline and somatic deletions of the Dβ1 nicotinic acetylcholine receptor subunit and investigate the consequences of loss of function in Drosophila melanogaster. Severe impacts on movement, male courtship, longevity, and wing expansion were found. Loss of Dβ1 was also associated with a reduction in transcript levels for the wing expansion hormone bursicon. Neuron-specific somatic deletion of Dβ1 in bursicon-producing neurons (CCAP-GAL4) was sufficient to disrupt wing expansion. Furthermore, CCAP-GAL4-specific expression of Dβ1 in a germline deletion background was sufficient to rescue the wing phenotype, pinpointing CCAP neurons as the neuronal subset requiring Dβ1 for the wing expansion pathway. Dβ1 is a known target of multiple commercially important insecticides, and the fitness costs exposed here explain why field-isolated target-site resistance has only been reported for amino acid replacements and not loss of function. This work reveals the importance of Dβ1-containing nicotinic acetylcholine receptors in CCAP neurons for robust bursicon-driven wing expansion.
No related grants have been discovered for Wei Chen.