Title: The use and manipulation of insect reproductive molecules for controlling insect populations Author
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 6, 2012
Publication Date: N/A
Technical Abstract: The use and manipulation of insect reproductive molecules, and the genes that encode them, provides a variety of methods to control insect fertility and thus a means of population control for insect pests. Towards this end, we first studied the yolk polypeptide gene from the caribfly, Anastrepha suspensa, so that its promoter might be used to express lethal genes in the adult fat body, causing female-specific lethality for male-only strains useful for SIT. Surprisingly, YP expression was limited solely to the ovaries, without apparent regulation by either juvenile hormone or 20-hydroxyecdysone, limiting use of the YP promoter to inducing female sterility. To isolate a testis-specific promoter that might allow male-specific sterility or sperm marking for SIT, the spermatocyte-specific ß2-tubulin gene was isolated from caribfly and other tephritids. The Asß2-tub promoter linked to the DsRed fluorescent protein gene resulted in testis-specific marking in transgenic caribflies and mexflies, with individual marked sperm identified in their testes, and in the spermathecae of mated females. Most recently, the transformer (tra) and transformer-2 (tra-2) genes from A. suspensa were isolated to study their role in sex determination and fertility, and possible uses for male-only strain development. Both genes are highly conserved in structure, regulation and function to those known from other tephritid species. Sex-specific transcripts for Astra were detected, one in females and three in males, whereas Astra-2 had a single common transcript found in both sexes. To test their function by transient RNAi, Astra and Astra-2 dsRNA was injected into A. suspensa embryos from a transgenic strain having a Y-linked DsRed marker integration, allowing XY males to be distinguished from XX phenotypic males. Nearly all XX embryos developed into fully masculinized phenotypic male adults with no apparent female morphology, though all were sterile, while XY males were fertile (unlike Drosophila). Abnormal hypertrophied gonads were revealed in XX pseudomales but not in the XY males, though only those injected with Astra-2 had motile sperm. Astra and Astra-2 were found to be both necessary for female development, presumably by a primary influence on doublesex transcripts, and the potential exists for producing a male-only population by knock-down of either gene or both together.