Applied insect genetics and functional conservation of regulatory elements between taxa

nsects cause enormous damage to crops, livestock and human health by direct feeding and by vectoring diseases. New, targeted control methods are urgently needed. One potential method is the Sterile Insect Technique (SIT) [1]. In SIT, irradiated (sterile) insects are released in large numbers; wild females mating sterile males have fewer or no progeny; if enough sterile insects are released for long enough, the target population can be controlled. SIT is very successful against several agricultural pests but has some limitations. One is that radiation-sterilisation damages many species to the extent that irradiated males cannot compete effectively for mates. Another is that single-sex (male-only) release is much more effective (and would eliminate damage from females, e.g. oviposition (tephritid fruit flies) or biting (mosquitoes)) however large-scale separation of males and females is difficult for most species. Finally, for some species, density-dependent effects point to late-acting lethality being substantially more effective than the early-acting lethality typical of radiation. Oxitec has developed genetic methods to overcome each of these difficulties, an approach termed RIDL [2-4]. Oxitec has developed strains of Aedes aegypti mosquitoes with repressible female-specific flightlessness ('RIDL strains'). Modelling shows that this late-acting, female-specific lethality (flightlessness would be lethal in the field) is much more effective than conventional SIT. Additionally, with a female-killing system, homozygous RIDL eggs could be distributed into the field; only males would emerge; these would go on to mate wild females. Egg release would be much cheaper than adult release. We propose to extend this technology to other mosquito species and, in time, to other vectors. A key issue relates to the degree of cross-species function of regulatory elements. Will elements from one species work in a different species? Different genus? Family? Order? Insect genetic engineering is a very new technology, with bespoke strains hand-made for particular applications; we need instead to develop a tool-box of off-the-shelf parts that can be quickly and reliably assembled for each new purpose. This same issue can equally be phrased as a gap in basic biology/functional genomics. At least in insects, a big part of this due to lack of data - we have little data on the function of heterologous promoters in any species other than D. melanogaster. The student will address one aspect of this in the context of genetic engineering of traits of real commercial and practical relevance. The key regulatory elements in Oxitec's female-flightless strains are derived from the Aedes aegypti Actin-4 gene [5]; these confer sex-, stage- and tissue-specificity. Components include promoter function and specificity, sex-specific alternative splicing. Will these elements have the same properties in other species? We are interested in other mosquitoes of the same genus, e.g. Ae. albopictus, also the much more distantly related Anophelines. Fortunately, we have a genome sequence from each of Aedes, Culex and Anopheles, and more will emerge during this studentship. We have identified a homolog of AeAct4 in An. gambiae and shown that it has the same expression pattern. The student will use regulatory sequences from both species to try to make transgenic female-flightless strains of Anopheles mosquitoes. Several species are of interest, with different degrees of relatedness to An. gambiae. The student will correlate sequence and function of the relevant control elements. 1 Sterile Insect Technique Dyck VA et al Eds; Springer 2005 2 Alphey L et al. In Transgenesis and the management of vector-borne disease; Aksoy, S., Ed.; Landes Bioscience 2007 3 Thomas D, Donnelly C, Wood R, Alphey L Science 2000, 287, 2474-6 4 Phuc HK ... Alphey, L. BMC Biology 2007, 5, 11 5 Muñoz D, et al. Insect Molecular Biology 2004, 13, 563-8