The European corn borer (
Understanding the molecular basis of repeated evolution improves our ability to predict evolution across the tree of life. Only since the last decade has high‐throughput sequencing enabled comparative genome scans to thoroughly examine the repeatability of genetic changes driving repeated phenotypic evolution. The Asian corn borer (ACB),
- PAR ID:
- 10406195
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Molecular Ecology
- Volume:
- 32
- Issue:
- 13
- ISSN:
- 0962-1083
- Format(s):
- Medium: X Size: p. 3419-3439
- Size(s):
- p. 3419-3439
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract Ostrinia nubilalis ) is an agricultural pest and burgeoning model for research on speciation, seasonal adaptation and insect resistance management. Although previous work inO. nubilalis has identified genes associated with differences in life cycle, reproduction, and resistance toBt toxins, the general lack of a robust gene‐editing protocol forO. nubilalis has been a barrier to functional validation of candidate genes. Here, we demonstrate an efficient and practical methodology for heritable gene mutagenesis inO. nubilalis using the CRISPR/Cas9 genome editing system. Precise loss‐of‐function (LOF) mutations were generated at two circadian clock genes,period (per ) andpigment‐dispersing factor receptor (pdfr ), and a developmental gene,prothoracicotropic hormone (ptth ). Precluding the need for a visible genetic marker, gene‐editing efficiency remained high across different single guide RNAs (sgRNA) and germline transmission of mutations to F1offspring approached 100%. When single or dual sgRNAs were injected at a high concentration, gene‐specific phenotypic differences in behaviour and development were identified in F0mutants. Specifically, F0gene mutants demonstrated that PER, but not PDFR, is essential for normal timing of eclosion. PTTH F0mutants were significantly heavier and exhibited a higher incidence of diapause. This work will accelerate future studies of gene function inO. nubilalis and facilitate the development of similar screens in other Lepidopteran and non‐model insects. -
more » « less
Abstract Reconstructing a robust phylogenetic framework is key to understanding the ecology and evolution of many economically important taxa. The crambid moth genus
Ostrinia contains multiple agricultural pests, and its classification and phylogeny has remained controversial because of the paucity of characters and the lack of clear morphological boundaries for its species. To address these issues, we inferred a molecular phylogeny ofOstrinia using a phylogenomic dataset containing 498 loci and 115 197 nucleotide sites and examined whether traditional morphological characters corroborate our molecular results. Our results strongly support the monophyly of one of theOstrinia species groups but surprisingly do not support the monophyly of the other two. Based on the extensive morphological examination and broadly representative taxon sampling of the phylogenomic analyses, we propose a revised classification of the genus, defined by three species groups (Ostrinia nubilalis species group,Ostrinia obumbratalis species group, andOstrinia penitalis species group), which differs from the traditional classification of Mutuura & Munroe (1970). Morphological and molecular evidence reveal the presence of a new North American species,Ostrinia multispinosa Yangsp.n. , closely related toO .obumbratalis . Our analyses indicate that theOstrinia ancestral larval host preference was for dicots, and thatO .nubilalis (European corn borer) andOstrinia furnacalis (Asian corn borer) independently evolved a preference for feeding on monocots (i.e., maize). Males of a fewOstrinia species have enlarged, grooved midtibiae with brush organs that are known to attract females to increase mating success during courtship, which may represent a derived condition. Our study provides a strong evolutionary framework for this agriculturally important insect lineage. -
more » « less
Abstract A major goal of modern biology is connecting phenotype with its underlying genetic basis. The Mexican cavefish (Astyanax mexicanus), a characin fish species comprised of a surface ecotype and a cave-derived ecotype, is well suited as a model to study the genetic mechanisms underlying adaptation to extreme environments. Here, we map 206 previously published quantitative trait loci (QTL) for cave-derived traits in A. mexicanus to the newest version of the surface fish genome assembly, AstMex3. These analyses revealed that QTL clusters in the genome more than expected by chance, and this clustering is not explained by the distribution of genes in the genome. To investigate whether certain characteristics of the genome facilitate phenotypic evolution, we tested whether genomic characteristics associated with increased opportunities for mutation, such as highly mutagenic CpG sites, are reliable predictors of the sites of trait evolution but did not find any significant trends. Finally, we combined the QTL map with previously collected expression and selection data to identify 36 candidate genes that may underlie the repeated evolution of cave phenotypes, including rgrb, which is predicted to be involved in phototransduction. We found this gene has disrupted exons in all non-hybrid cave populations but intact reading frames in surface fish. Overall, our results suggest specific regions of the genome may play significant roles in driving adaptation to the cave environment in A. mexicanus and demonstrate how this compiled dataset can facilitate our understanding of the genetic basis of repeated evolution in the Mexican cavefish.
-
more » « less
Abstract Tamarix austromongolica is endemic to the Yellow River Basin and has adapted to diverse ecological settings in the region, including the arid areas of northwestern China and the saline soil regions of the Yellow River Delta. However, the genetic basis of its local adaptation remains unclear. We report a chromosome-level assembly of the T. austromongolica genome based on PacBio high-fidelity sequencing and Hi-C technology. The 12 pseudochromosomes cover 98.44% of the 1.32 Gb assembly, with a contig N50 of 52.57 Mb and a BUSCO score of 98.2%. The genome comprises 913.6 Mb (68.83%) of repetitive sequences and 22,374 protein-coding genes. Genome evolution analyses suggest that genes under positive selection and significantly expanded gene families have facilitated T. austromongolica’s adaptability to diverse environmental factors and high resistance to diseases. Using genotyping-by-sequencing, we conducted population structure and selection analyses of 114 samples from 15 sites. Two genetic groups were identified, and 114 and 289 candidate genes were assigned to the populations of the northwestern and eastern parts of the Yellow River, respectively. Furthermore, we discovered numerous candidate genes associated with high-altitude adaptability and salt tolerance. This research provides valuable genomic resources for the evolutionary study and genetic breeding of tamarisk.
-
more » « less
Abstract Artificial light at night (ALAN) is an increasingly important form of environmental disturbance as it alters Light:Dark cycles that regulate daily and seasonal changes in physiology and phenology. The Northern house mosquito (
Culex pipiens ) and the tiger mosquito (Aedes albopictus ) enter an overwintering dormancy known as diapause that is cued by short days. These two species differ in diapause strategy:Cx. pipiens diapause as adult females whileAe. albopictus enter a maternally-programmed, egg diapause. Previous studies found that ALAN inhibits diapause in both species, but the mechanism is unknown. As the circadian clock is implicated in the regulation of diapause in many insects, we examined whether exposure to ALAN altered the daily expression of core circadian cloc genes (cycle ,Clock ,period ,timeless ,cryptochrome 1 ,cryptochrome 2 , andPar domain protein 1 ) in these two species when reared under short-day, diapause-inducing conditions. We found that exposure to ALAN altered the abundance of several clock genes in adult females of both species, but that clock gene rhythmicity was maintained for most genes. ALAN also had little effect on clock gene abundance in mature oocytes that were dissected from femaleAe. albopictus that were reared under short day conditions. Our findings indicate that ALAN may inhibit diapause initiation through the circadian clock in two medically-important mosquitoes.
