Sex Determination Mechanisms in the Calliphoridae (Blow Flies)

Abstract

The Calliphoridae or blow flies are a family of insects that occupy diverse habitats and perform important ecological roles, particularly the decomposition of animal remains. Some Calliphoridae species are also important in the forensic sciences, in agriculture (e.g. as livestock pests) and in medicine (e.g. maggot therapy). Calliphoridae provide striking examples in support of the hypothesis that sex determination regulatory gene hierarchies evolve in the reverse order, with the gene at the top being the most recently added. Unlike the model fly Drosophila melanogaster, where sex is determined by the number of X chromosomes, in the Australian sheep blow fly (Lucilia cuprina) sex is determined by a Y-linked male-determining gene (M). A different regulatory system appears to operate in the hairy maggot blow fly (Chrysomya rufifacies) where the maternal genotype determines sex. It is hypothesized that females heterozygous for a dominant female-determining factor (F/f) produce only female offspring and homozygous f/f females produce only sons. The bottom of the regulatory hierarchy appears to be the same in D. melanogaster and L. cuprina, with sex-specific splicing of doublesex transcripts being controlled by the female-specific Transformer (TRA) protein. We discuss a model that has been proposed for how tra transcripts are sex-specifically spliced in calliphorids, which is very different from D. melanogaster.

The Evolving Puzzle of AutosomalVersusY-linked Male Determination inMusca domestica

“…Zygotes carrying an M factor developed into males regardless of whether the mother had one or two copies of this tra mutation (Inoue and Hiroyoshi 1986). The house fly tra mutation produces a situation reminiscent of that observed in naturally occurring systems in which maternal genotype determines sex, such as Chrysomya rufifacies , suggesting a mutational mechanism by which maternal effect sex determination can evolve (Scott et al 2014b). …”

Agricultural production: assessment of the potential use of Cas9-mediated gene drive systems for agricultural pest control

“…An unknown Y-linked male-determining gene switches off tra in males ( Figure 2). In females, tra switches the doublesex and fruitless genes into their 'femalemode', which leads to female development and behavior (Scott, Pimsler, and Tarone 2014). In the absence of tra activity, XX females develop as phenotypic males.…”

“…Remarkably, the genetic mechanisms that determine sex in the red flour beetle, T. casteneum, appear to be very similar to the L. cuprina regulatory hierarchy. Adapted from Scott, Pimsler, and Tarone (2014) and Shukla and Palli (2013).…”

Functional characterization of calliphorid cell death genes and cellularization gene promoters for controlling gene expression and cell viability in early embryos

“…Through comparisons of the encoded proteins with orthologues from other Diptera, we identify motifs conserved in the cellularization and proapoptotic proteins. The isolated cellularization gene promoters provide the ability to control gene expression in the early zygote, which will have multiple applications such as building a TESS and the potential ability to manipulate the sex determination system (Scott et al ., ).…”