Intersex (ix) mutations of Drosophila melanogaster cause nonrandom cell death in genital disc and can induce tumours in genitals in response to decapentaplegic (dpp disk ) mutations

Abstract

In Drosophila melanogaster, the intersex (ix) is a terminally positioned gene in somatic sex determination hierarchy and function with the female specific product of double sex (DSX(F)) to implement female sexual differentiation. The null phenotype of ix is to transform diplo-X individuals into intersexes while leaving haplo-X animals unaffected. This study on the effect of different intersex mutations on genital disc development provides the following major results: (i) similar range of a characteristic array of morphological structures (from almost double sex terminalia to extreme reduction of terminal appendages) was displayed by the terminalia of XX ix(1)/ix(1) , XX ix(2)/ix(2) and XX ix(5)/ix(5) individuals; (ii) an increased number of apoptotic cells were found to occur in a localized manner in mature third instar larval genital discs of ix individuals; (iii) ix mutations can induce high frequency of neoplastic tumours in genitals in the presence of decapentaplegic (dpp(disk)) mutations; and (iv) heteroallelic combinations of dpp(disk) mutations can also induce tumours in intersex genitals with variable expressivity. On the basis of these findings, we suggest that: (i) loss of function of ix causes massive cell death in both male and female genital primordia of genital discs, resulting phenotype mimicking in male and female characteristics in genitals; and (ii) at the discs, the apoptotic cells persist as 'undead' cells that can induce oncogenic transformation in the neighbouring disc cells when dpp signalling is blocked or reduced by dpp(disk) mutations.

A Standardized Nomenclature and Atlas of the Male Terminalia of <em>Drosophila melanogaster</em>

“…The earliest of these is ontogeny, which aimed at identifying the segmental origin of the different structures and how they sexually differentiate during development from the larval genital disc in D. melanogaster. It is thanks to this discipline that the 'traditional terminology' was established (Dobzhansky 1930;Ferris 1950;Bryant 1978) and continues to be used by contemporary developmental biologists (Chatterjee et al 2015). Most of the terms currently annotated in FlyBase (www.flybase.org) are based on the traditional system.…”

Intersex is required for female sexual development in Hermetia illucens

“…IX acts in concert with DSX to regulate terminal sexual differentiation (Garrett-Engele & Siegal et al, 2002). Yeast 1-hybrid and immunoprecipitation assays demonstrated that IX interacts with DSX F , but not DSX M (Garrett-Engele & Siegal, 2002;Siegal & Baker, 2005;Chatterjee et al, 2015). In D. melanogaster, ix has no introns, only a single mRNA transcript is detected (Siegal & Baker, 2005).…”

A standardized nomenclature and atlas of the male terminalia ofDrosophila melanogaster

“…The earliest of these is ontogeny, which aimed at identifying the segmental origin of the different structures and how they sexually differentiate during development from the larval genital disc in D. melanogaster. It is thanks to this discipline that the 'traditional terminology' was established [2][3][4] and continues to be used by contemporary developmental biologists [5]. Most of the terms currently annotated in FlyBase (www.…”