Parental RNAi Silencing of the transformer-2 Gene in a Species of the Anastrepha fraterculus Complex of Cryptic Species (Diptera, Tephritidae)

In genera Anastrepha, Bactrocera and Ceratitis of the tephritid fruit flies the auto-regulatory function of gene transformer is assumed to be activated by maternal derived mRNA or the proteins of the gene transformer (tra-2 mat) and transformer-2 (tra-2mat). However, this maternal effect was not yet been demonstrated. The objective of the present study was to test the effect of absence of tra-2mat in the eggs on the sex determination of A. sp.1 affinis fraterculus. This was achieved by silencing gene tra-2 in the parental females via the pRNA interference. The data showed that tra-2 was transiently silenced in the female for three weeks period. The progenies sex ratio produced by these females during the silencing of tra-2 depart from 1-1 in favor of males. The excess of males was due to the transformation of a fraction of genotypical female XX embryos into XX males, the so-called pseudomales, Individual F1 males from the offspring of treated females crossed to females from the stock, revealed that majority of them showed regular mating behavior and were fertile. However, no offspring was produced in the crosses by a fraction of males that have produced sperms, showed regular mating behavior but did not transfer sperms to the females. The data allow the conclusion that the absence of tra-2mat in the eggs had impaired the self-regulation of the embryonic gene tra resulting in the transformation of XX embryos into pseudomales and also that these pseudomales are sterile. This effect may be useful improve more sustainable technologies for fruit fly control such as SIT.