8-HQA adjusts the number and diversity of bacteria in the gut microbiome of Spodoptera littoralis

Quinolinic carboxylic acids are known for their metal ion chelating properties in insects, plants and bacteria. The larval stages of the lepidopteran pest, Spodoptera littoralis, produce 8-hydroxyquinoline-2-carboxylic acid (8-HQA) in high concentrations from tryptophan in the diet. At the same time, the larval midgut is known to harbor a bacterial population. The motivation behind the work was to investigate whether 8-HQA is controlling the bacterial community in the gut by regulating the concentration of metal ions. Knocking out the gene for kynurenine 3-monooxygenase (KMO) in the insect using CRISPR/Cas9 eliminated production of 8-HQA and significantly increased bacterial numbers and diversity in the larval midgut. Adding 8-HQA to the diet of knockout larvae caused a dose-dependent reduction of bacterial numbers with minimal effects on diversity. Enterococcus mundtii dominates the community in all treatments, probably due to its highly efficient iron uptake system and production of the colicin, mundticin. Thus host factors and bacterial properties interact to determine patterns of diversity and abundance in the insect midgut

Geographic Variation in Sexual Attraction of Spodoptera frugiperda Corn- and Rice-Strain Males to Pheromone Lures

The corn- and rice-strains of Spodoptera frugiperda exhibit several genetic and behavioral differences and appear to be undergoing ecological speciation in sympatry. Previous studies reported conflicting results when investigating male attraction to pheromone lures in different regions, but this could have been due to inter-strain and/or geographic differences. Therefore, we investigated whether corn- and rice-strain males differed in their response to different synthetic pheromone blends in different regions in North America, the Caribbean and South America. All trapped males were strain typed by two strain-specific mitochondrial DNA markers. In the first experiment, we found a nearly similar response of corn and rice-strain males to two different 4-component blends, resembling the corn- and rice-strain female blend we previously described from females in Florida. This response showed some geographic variation in fields in Canada, North Carolina, Florida, Puerto Rico, and South America (Peru, Argentina). In dose-response experiments with the critical secondary sex pheromone component (Z)-7-dodecenyl acetate (Z7-12:OAc), we found some strain-specific differences in male attraction. While the response to Z7-12:OAc varied geographically in the corn-strain, rice-strain males showed almost no variation. We also found that the minor compound (Z)-11-hexadecenyl acetate (Z11-16:OAc) did not increase attraction of both strains in Florida and of corn-strain males in Peru. In a fourth experiment, where we added the stereo-isomer of the critical sex pheromone component, (E)-7-dodecenyl acetate, to the major pheromone component (Z)-9-tetradecenyl acetate (Z9-14:OAc), we found that this compound was attractive to males in North Carolina, but not to males in Peru. Overall, our results suggest that both strains show rather geographic than strain-specific differences in their response to pheromone lures, and that regional sexual communication differences might cause geographic differentiation between populations.Fil: Unbehend, Melanie. Instituto Max Planck Institut Fur Chemische Okologie; AlemaniaFil: Hänniger, Sabine. Instituto Max Planck Institut Fur Chemische Okologie; AlemaniaFil: Vasquez, Gissella M.. University Of North Carolina; Estados UnidosFil: Juárez, María Laura. Gobierno de Tucumán. Ministerio de Desarrollo Productivo. Estación Experimental Agroindustrial Obispo Colombres; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán; ArgentinaFil: Reisig, Dominic. University Of North Carolina; Estados UnidosFil: Mcneil, Jeremy N.. University of Western Ontario. Department of Biology; CanadáFil: Meagher, Robert L.. United States Department Of Agriculture; Estados UnidosFil: Jenkins, David A.. United States Department of Agriculture; ArgentinaFil: Heckel, David G.. Instituto Max Planck Institut Fur Chemische Okologie; AlemaniaFil: Groot, Astrid T.. University Of Amsterdam; Países Bajos. Instituto Max Planck Institut Fur Chemische Okologie; Alemani

Adaptation by copy number variation increases insecticide resistance in fall armyworms

Insecticide resistance is a major main challenge in pest control, and understanding its genetic basis is a key topic in agricultural ecology. Detoxification genes are well-known genetic elements that play a key role in adaptation to xenobiotics. The adaptive evolution of detoxification genes by copy number variations has been interpreted as a cause of insecticide resistance. However, the same pattern can be generated by the adaptation to host-plant defense toxins as well. In this study, we tested in fall armyworms (Lepidoptera Spodoptera frugiperda) if adaptation by copy number variation is the cause of the increased level of insecticide resistance from two geographic populations with different levels of resistance and two strains with different host plants. Following the generation of an assembly with chromosome-sized scaffolds (N50 = 13.2Mb), we observed that these two populations show a significant allelic differentiation of copy number variations, which is not observed between strains. In particular, a locus with almost complete allelic differentiation (Fst > 0.8) includes a cluster of P450 genes, which are well-known key players in detoxification. Detoxification genes are overrepresented in the genes with copy number variations, and the observed copy number variation appears to have beneficial effects in general. From this result, we concluded that copy number variation of detoxification genes in fall armyworms plays a key role in the insecticide resistance but not in the adaptation to host-plants, suggesting that the evolution of insecticide resistance may occur independently from host-plant adaptation

Adaptation by copy number variation increases insecticide resistance in the fall armyworm

International audienceUnderstanding the genetic basis of insecticide resistance is a key topic in agricultural ecology. The adaptive evolution of multi-copy detoxification genes has been interpreted as a cause of insecticide resistance, yet the same pattern can also be generated by the adaptation to host-plant defense toxins. In this study, we tested in the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), if adaptation by copy number variation caused insecticide resistance in two geographically distinct populations with different levels of resistance and the two host-plant strains. We observed a significant allelic differentiation of genomic copy number variations between the two geographic populations, but not between host-plant strains. A locus with positively selected copy number variation included a CYP gene cluster. Toxicological tests supported a central role for CYP enzymes in deltamethrin resistance. Our results indicate that copy number variation of detoxification genes might be responsible for insecticide resistance in fall armyworm and that evolutionary forces causing insecticide resistance could be independent of host-plant adaptation

Composition of pheromone lures used to attract <i>Spodoptera frugiperda</i> males in the field.

1<p>Compound concentrations were as follows: 100% = 300 µg, 18% = 54 µg, 13% = 39 µg, 10% = 30 µg, 8% = 24 µg, 4% = 12 µg, 2% = 6 µg, 1% = 3 µg.</p>2<p>Blend 1 and Blend 2 were based on the pheromone gland composition of Florida corn- and rice-strain females, respectively <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0089255#pone.0089255-Unbehend1" target="_blank">[52]</a>.</p

Attraction of corn-strain (A) and rice-strain (B) males to different doses of Z11-16:OAc.

<p>Bars represent the mean percentage of males caught per trap (0%, 8%, 13%, or 18% Z11-16:OAc +100% Z9-14:OAc +2% Z7-12:OAc) and per biological replicate (n = 3). Error bars show the variation between biological replicates (n = 3). Numbers in the bars represent the total number of males caught. n.s. = not significant. Data from Florida are adapted from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0089255#pone.0089255-Unbehend1" target="_blank">[52]</a>.</p

Test statistics on the <i>Spodoptera frugiperda</i> male trap catches of different experiments.

<p>Experiments A (Test of two 4-component blends: Blend 1 and Blend 2) and B (Z7-12:OAc dose-response experiment) were analyzed individually using square root transformed data in a MANOVA and a Wilks’ Lambda test. Bold P-values show a significant effect of geographic region, strain-identity of males, and/or the field crop, influencing the attraction of fall armyworm males to synthetic pheromone blends. Mean values and standard errors are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0089255#pone-0089255-g001" target="_blank">Figure 1</a> (Exp. A) and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0089255#pone-0089255-g002" target="_blank">Figure 2</a> (Exp. B).</p

<i>Spodoptera frugiperda</i> male trapping experiments conducted in North America, the Caribbean and South America.

1<p>Experiments: A) Test of two 4-component blends (Blend 1 and Blend 2), B) Z7-12:OAc dose-response, C) Z11-16:OAc dose-response, D) Importance of E7-12:OAc.</p>2<p>Data adapted from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0089255#pone.0089255-Unbehend1" target="_blank">[52]</a>.</p

Attraction of corn-strain (A) and rice-strain (B) males to different doses of Z7-12:OAc.

<p>Bars represent the mean percentage of males caught per trap (0%, 2%, 4%, or 10% Z7-12:OAc +100% Z9-14:OAc) and per biological replicate (n = 3). Different letters above the bars indicate significant differences. Error bars show the variation between biological replicates (n = 3). Numbers in brackets/bars represent the total number of males caught. Data from Florida are adapted from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0089255#pone.0089255-Unbehend1" target="_blank">[52]</a>.</p