A conserved female-specific larval requirement for MtnB function facilitates sex separation in multiple species of disease vector mosquitoes

Abstract

Background Clusters of sex-specific loci are predicted to shape the boundaries of the M/m sex-determination locus of the dengue vector mosquito Aedes aegypti, but the identities of these genes are not known. Identification and characterization of these loci could promote a better understanding of mosquito sex chromosome evolution and lead to the elucidation of new strategies for male mosquito sex separation, a requirement for several emerging mosquito population control strategies that are dependent on the mass rearing and release of male mosquitoes. This investigation revealed that the methylthioribulose-1-phosphate dehydratase (MtnB) gene, which resides adjacent to the M/m locus and encodes an evolutionarily conserved component of the methionine salvage pathway, is required for survival of female larvae. Results Larval consumption of Saccharomyces cerevisiae (yeast) strains engineered to express interfering RNA corresponding to MtnB resulted in target gene silencing and significant female death, yet had no impact on A. aegypti male survival or fitness. Integration of the yeast larvicides into mass culturing protocols permitted scaled production of fit adult male mosquitoes. Moreover, silencing MtnB orthologs in Aedes albopictus, Anopheles gambiae, and Culex quinquefasciatus revealed a conserved female-specific larval requirement for MtnB among different species of mosquitoes. Conclusions The results of this investigation, which may have important implications for the study of mosquito sex chromosome evolution, indicate that silencing MtnB can facilitate sex separation in multiple species of disease vector insects. Graphical Abstract

A Broad-Based Mosquito Yeast Interfering RNA Pesticide Targeting Rbfox1 Represses Notch Signaling and Kills Both Larvae and Adult Mosquitoes

“…The dosage of Rbfox1.457 correlated directly with the percentage of larval mortality (Figure 1f), with the LD 50 determined to be 28 mg. Larvicide activity was also verified in semi-field trials conducted at an outdoor rooftop laboratory in Notre Dame, IN, where 93 ± 1% larval mortality was observed following Rbfox1.457 treatment (Figure 1d; p < 0.001 vs. control). These studies, combined with previous studies in which yeast IRP larvicides were shown to function in different types of water [10,11] and in an assortment of different sized containers with varied water volumes and larval densities [6,10,11,32,33] provide further evidence that yeast IRPs may represent a new larvicidal intervention, adding Rbfox1.457 to the growing arsenal of yeast larvicides.…”

Selective targeting of biting females to control mosquito-borne infectious diseases

“…Promising strategies of female killing have been pursued based on larval consumption of the yeast Saccharomyces cerevisiae engineered to deliver interfering RNA to specifically kill females. RNAi-mediated silencing of gamma-glutamyl transpeptidase (GGT), methylthioribulose 1-phosphate dehydratase (MtnB), and lncRNA genes resulted in significant female death and no impact on male survival or fitness [55][56][57]. This system is advantageous as heat-killed yeast retains its ability to induce effective gene silencing, making packaging, shipping, and storage of this diet straightforward and extremely cost-effective.…”

Finding divergent sequences of homomorphic sex chromosomes via diploidized nanopore-based assembly from a single male

“…This differentiation was detected as a difference in the read depth of coverage (Matthews et al 2018) and the frequency of SNPs between males and females (Fontaine et al 2017). Additionally, several studies have reported sex-specific lethality when genes in the vicinity of the M-locus were recombined or silenced via RNAi (Krzywinska et al 2016; Wood 1990; Mysore et al 2021b). Moreover, an unexpected mechanism of inheritance bias in males was recently detected for a gene closely-linked to the M-locus that was targeted by a gene drive element (Verkuijl et al 2022).…”