RESUMO
Alternative, biologically-based approaches for pest management are sorely needed and one approach is to use genetically engineered insects. Herein we describe a series of integrated field, laboratory and modeling studies with the diamondback moth, Plutella xylostella, a serious global pest of crucifers. A "self-limiting" strain of Plutella xylostella (OX4319L), genetically engineered to allow the production of male-only cohorts of moths for field releases, was developed as a novel approach to protect crucifer crops. Wild-type females that mate with these self-limiting males will not produce viable female progeny. Our previous greenhouse studies demonstrated that releases of OX4319L males lead to suppression of the target pest population and dilution of insecticide-resistance genes. We report results of the first open-field release of a non-irradiated, genetically engineered self-limiting strain of an agricultural pest insect. In a series of mark-release-recapture field studies with co-releases of adult OX4319L males and wild-type counterparts, the dispersal, persistence and field survival of each strain were measured in a 2.83 ha cabbage field. In most cases, no differences were detected in these parameters. Overall, 97.8% of the wild-type males and 95.4% of the OX4319L males recaptured dispersed <35 m from the release point. The predicted persistence did not differ between strains regardless of release rate. With 95% confidence, 75% of OX4319L males released at a rate of 1,500 could be expected to live between 3.5 and 5.4 days and 95% of these males could be expected to be detected within 25.8-34.9 m from the release point. Moth strain had no effect on field survival but release rate did. Collectively, these results suggest similar field behavior of OX4319L males compared to its wild-type counterpart. Laboratory studies revealed no differences in mating competitiveness or intrinsic growth rates between the strains and small differences in longevity. Using results from these studies, mathematical models were developed that indicate release of OX4319L males should offer efficacious pest management of P. xylostella. Further field studies are recommended to demonstrate the potential for this self-limiting P. xylostella to provide pest suppression and resistance management benefits, as was previously demonstrated in greenhouse studies.
RESUMO
Dosage compensation is the fundamental process by which gene expression from the male monosomic X chromosome and from the diploid set of autosomes is equalized. Various molecular mechanisms have evolved in different organisms to achieve this task. In Drosophila, genes on the male X chromosome are upregulated to the levels of expression from the two X chromosomes in females. To test whether a similar mechanism is operating in immature stages of Anopheles mosquitoes, we analyzed global gene expression in the Anopheles gambiae fourth instar larvae and pupae using high-coverage RNA-seq data. In pupae of both sexes, the median expression ratios of X-linked to autosomal genes (X:A) were close to 1.0, and within the ranges of expression ratios between the autosomal pairs, consistent with complete compensation. Gene-by-gene comparisons of expression in males and females revealed mild female bias, likely attributable to a deficit of male-biased X-linked genes. In larvae, male to female ratios of the X chromosome expression levels were more female biased than in pupae, suggesting that compensation may not be complete. No compensation mechanism appears to operate in male germline of early pupae. Confirmation of the existence of dosage compensation in A. gambiae lays the foundation for research into the components of dosage compensation machinery in this important vector species.