Structure and organization of amplicons containing the E4 esterase genes responsible for insecticide resistance in the aphid Myzus persicae (Sulzer).
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ABSTRACT:
SUBMITTER: Field LM
PROVIDER: S-EPMC1218268 | biostudies-other | 1997 Mar
REPOSITORIES: biostudies-other
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Project description:The amplification of genes encoding an insecticide-detoxifying esterase (E4) in the peach-potato aphid Myzus persicae is one of the few examples where this genetic phenomenon has been shown to be involved in the response of an intact higher organism to artificial selection. Here we report quantitative and qualitative studies of the repeat units (amplicons) containing the E4 genes in a highly resistant aphid clone. Initial studies to quantify esterase sequences showed a 5-11-fold increase in resistant aphids compared with susceptible aphids, suggesting the presence of 10-22 gene copies per diploid genome. A more incisive analysis by pulsed-field gel electrophoresis confirmed the presence of about 12 copies of the E4 gene and showed them to be on about 24 kb amplicons, arranged as a tandem array of direct repeats. This, together with previous results from crossing experiments and with recent in situ hybridization studies, confirms that the E4 gene amplification in this aphid clone is heterozygous at a single locus. However, these data show that the gene amplification alone cannot account for the approx. 60 times higher levels of E4 protein and its mRNA present in this aphid clone, and therefore resistance must involve changes in both esterase gene copy number and gene expression.
| S-EPMC1216941 | biostudies-other
Project description:The amplification of genes encoding the esterases E4 and FE4 is a widespread mechanism of insecticide resistance in the peach-potato aphid, Myzus persicae (Sulzer). We present evidence that in susceptible aphids the two genes are adjacent to each other in a head-to-tail arrangement with E4 upstream of FE4 and with approx. 19 kb of intervening sequence. There are also at least two other closely related sequences which might come from other members of an esterase gene family, in line with reports of other insect gene families encoding detoxifying enzymes. The close identity between E4 and FE4 genes indicates a recent duplication and divergence. The subsequent amplifications giving multiple copies of either E4 or FE4 must have involved two separate events, each probably occurring once and then being selected by insecticide exposure and spread by migration. The cloning of sequences upstream of the FE4 gene suggest, by comparison with E4, that the two genes are regulated in different ways. FE4 has sequences corresponding to a conventional promoter (TATA box and CAP site) that are not present in E4; on the other hand, FE4 lacks the CpG island present 5' of E4 genes that may control expression through changes in DNA methylation. The differences are likely to have occurred by the duplication event that gave rise to E4 and FE4 leading to different 5' sequences.
| S-EPMC1219123 | biostudies-other
Project description:Full-length cDNA clones encoding the esterases (E4 and FE4) that confer insecticide resistance in the peach-potato aphid [Myzus persicae (Sulzer)] were isolated and characterized. The E4 cDNA contained an open reading frame of 1656 nucleotides, coding for a protein of 552 amino acids. The FE4 cDNA shared 99% identity with E4 over this region, the most important difference being a single nucleotide substitution resulting in the FE4 mRNA having an extra 36 nucleotides at the 3' end. The derived amino acid sequences for the N-terminus of E4 and FE4 were identical, with the first 23 residues being characteristic of a signal peptide and the next 40 residues being an exact match to the N-terminal sequence determined by Edman degradation of both purified proteins. The predicted molecular masses of 58.8 and 60.2 kDa for the E4 and FE4 polypeptides were consistent with those previously observed by in vitro translation of mRNA. Five potential N-linked glycosylation sites were present in both polypeptides, in accordance with earlier evidence that the native esterases are glycoproteins. Comparison of the aphid esterase protein sequences with other serine hydrolases provided evidence that their activity involves a charge-relay system with a catalytic triad the same as that found in acetylcholinesterase. Restriction mapping and sequencing of cloned genomic DNA showed that the E4 gene is spread over 4.3 kb with six introns and that the previously reported differences between the 3' ends of the E4 and FE4 genes result from single nucleotide substitutions and not gross differences in the DNA sequences.
| S-EPMC1134493 | biostudies-other
Project description:Most populations of the aphid Myzus persicae have amplified genes (up to 80 copies) encoding the insecticide-detoxifying esterase E4. This paper reports the analysis of methylation of the E4 gene and its flanking DNA with the use of methylation-sensitive restriction enzymes, CpG profiling and bisulphite sequencing. In combination these show that E4 has 5-methylcytosine confined to CpG doublets, as previously shown for vertebrate genomes; this is the first such report for an insect gene. The methylation is present within the gene but absent from upstream regions, including the 5' CpG-rich region around the start of transcription, and from 3' flanking DNA. Methylated E4 genes are expressed; loss of the 5-methylcytosine is correlated with a loss of transcription, although this is not accompanied by a global loss of the 5-methylcytosine present in the aphid genome. These results suggest that the methylation of E4 has a positive role in expression, and call into question the widely held view that methylation in invertebrate genomes is confined to regions that do not contain genes and that methylation is always associated with gene silencing.
| S-EPMC1221215 | biostudies-other
Project description:Overproduction of the insecticide-degrading esterases, E4 and FE4, in peach-potato aphids, Myzus persicae (Sulzer), depends on both gene amplification and transcriptional control, the latter being associated with changes in DNA methylation. The structure and function of the aphid esterase genes have been studied but the determination of their copy number has proved difficult, a common problem with gene amplification. We have now used a combination of pulsed-field gel electrophoresis and quantitative competitive PCR to determine relative esterase gene copy numbers in aphid clones with different levels of insecticide resistance (R1, R2 and R3). There are approx. 4-fold increases between susceptible, R1, R2 and R3 aphids, reaching a maximum of approx. 80 times more genes in R3; this gives proportionate increases in esterase protein relative to susceptible aphids. Thus there is no overexpression of the amplified genes, in contrast with what was thought previously. For E4 genes, the loss of 5-methylcytosine is correlated with a loss of expression, greatly decreasing the amount of enzyme relative to the copy number.
| S-EPMC1220211 | biostudies-other
Project description:The peach potato aphid, Myzus persicae (Sulzer), is a worldwide pest of many crops, and the most important aphid pest of peach and potato crops in Tunisia, mainly due to virus transmission, for which insecticides are frequently applied. We studied the genetic structure of M. persicae populations in Tunisia, in order to further our understanding of the biotic and abiotic factors shaping populations and to predict their evolutionary responses to the present management practices. We monitored peach orchards and seed potato crops in different seasons and regions from 2011-2013 and in 2016 (19 populations), assessing the genetic diversity of M. persicae at six microsatellite loci. Temporal and spatial changes in the frequency and distribution of 397 genotypes in 548 sampled aphids were studied. Only 37 genotypes were found more than once (clonal amplification), as most genotypes were found only once (91.60% in peach; 88.73% in potato crops). A similarly high genetic diversity was observed in aphids sampled from peach (G/N = 0.76; Ho = 0.617) and potato (G/N = 0.70; Ho = 0.641). Only a weak genetic differentiation among populations was found, mainly between geographic locations. Clustering analysis revealed genotypes to be grouped mainly according to host plant. The availability of the primary host, high proportion of unique genotypes, high genetic diversity and lack of structuring suggest that the aphid reproduces mainly through cyclical parthenogenesis in Tunisia. On the other hand, we provide a farm-scale study that shows how easily M. persicae can colonize different areas and hosts, which may have important implications in relation to plant virus vectoring.
| S-EPMC6835240 | biostudies-literature
Project description:The evolution of resistance to insecticides threatens the sustainable control of many of the world's most damaging insect crop pests and disease vectors. To effectively combat resistance, it is important to understand its underlying genetic architecture, including the type and number of genetic variants affecting resistance and their interactions with each other and the environment. While significant progress has been made in characterizing the individual genes or mutations leading to resistance, our understanding of how genetic variants interact to influence its phenotypic expression remains poor. Here, we uncover a mechanism of insecticide resistance resulting from transposon-mediated insertional mutagenesis of a genetically dominant but insecticide-susceptible allele that enables the adaptive potential of a previously unavailable recessive resistance allele to be unlocked. Specifically, we identify clones of the aphid pest Myzus persicae that carry a resistant allele of the essential voltage-gated sodium channel (VGSC) gene with the recessive M918T and L1014F resistance mutations, in combination with an allele lacking these mutations but carrying a Mutator-like element transposon insertion that disrupts the coding sequence of the VGSC. This results in the down-regulation of the dominant susceptible allele and monoallelic expression of the recessive resistant allele, rendering the clones resistant to the insecticide bifenthrin. These findings are a powerful example of how transposable elements can provide a source of evolutionary potential that can be revealed by environmental and genetic perturbation, with applied implications for the control of highly damaging insect pests.
| S-EPMC8201860 | biostudies-literature
Project description:BackgroundAphid attack induces defense responses in plants activating several signaling cascades that led to the production of toxic, repellent or antinutritive compounds and the consequent reorganization of the plant primary metabolism. Pepper (Capsicum annuum L.) leaf proteomic response against Myzus persicae (Sulzer) has been investigated and analyzed by LC-MS/MS coupled with bioinformatics tools.ResultsInfestation with an initially low density (20 aphids/plant) of aphids restricted to a single leaf taking advantage of clip cages resulted in 6 differentially expressed proteins relative to control leaves (3 proteins at 2 days post-infestation and 3 proteins at 4 days post-infestation). Conversely, when plants were infested with a high density of infestation (200 aphids/plant) 140 proteins resulted differentially expressed relative to control leaves (97 proteins at 2 days post-infestation, 112 proteins at 4 days post-infestation and 105 proteins at 7 days post-infestation). The majority of proteins altered by aphid attack were involved in photosynthesis and photorespiration, oxidative stress, translation, protein folding and degradation and amino acid metabolism. Other proteins identified were involved in lipid, carbohydrate and hormone metabolism, transcription, transport, energy production and cell organization. However proteins directly involved in defense were scarce and were mostly downregulated in response to aphids.ConclusionsThe unexpectedly very low number of regulated proteins found in the experiment with a low aphid density suggests an active mitigation of plant defensive response by aphids or alternatively an aphid strategy to remain undetected by the plant. Under a high density of aphids, pepper leaf proteome however changed significantly revealing nearly all routes of plant primary metabolism being altered. Photosynthesis was so far the process with the highest number of proteins being regulated by the presence of aphids. In general, at short times of infestation (2 days) most of the altered proteins were upregulated. However, at longer times of infestation (7 days) the protein downregulation prevailed. Proteins involved in plant defense and in hormone signaling were scarce and mostly downregulated.
| S-EPMC7788789 | biostudies-literature
Project description:Myzus persicae (Sulzer) is an important insect pest in agriculture that has a very broad host range. Previous research has shown that the microbiota of insects has implications for their growth, development, and environmental adaptation. So far, there is little detailed knowledge about the factors that influence and shape the microbiota of aphids. In the present study, we aimed to investigate diet-induced changes in the microbiome of M. persicae using high-throughput sequencing of bacterial 16S ribosomal RNA gene fragments in combination with molecular and microbiological experiments. The transfer of aphids to different plants from the Solanaceae family resulted in a substantial decrease in the abundance of the primary symbiont Buchnera. In parallel, a substantial increase in the abundance of Pseudomonas was observed; it accounted for up to 69.4% of the bacterial community in M. persicae guts and the attached bacteriocytes. In addition, we observed negative effects on aphid population dynamics when they were transferred to pepper plants (Capsicum annuum L.). The microbiome of this treatment group showed a significantly lower increase in the abundance of Pseudomonas when compared with the other Solanaceae plant diets, which might be related to the adaptability of the host to this diet. Molecular quantifications of bacterial genera that were substantially affected by the different diets were implemented as an additional verification of the microbiome-based observations. Complementary experiments with bacteria isolated from aphids that were fed with different plants indicated that nicotine-tolerant strains occur in Solanaceae-fed specimens, but they were not restricted to them. Overall, our mechanistic approach conducted under controlled conditions provided strong indications that the aphid microbiome shows responses to different plant diets. This knowledge could be used in the future to develop environmentally friendly methods for the control of insect pests in agriculture.
| S-EPMC8287905 | biostudies-literature
Project description:Myzus persicae isolate:Myzus persicae Sulzer Raw sequence reads
| PRJNA445935 | ENA