Extraordinary pH - the mechanism of generation of pH 12 in living systems

Insects are both vital and deadly in their interactions with humans. Although nearly all the world's crops are pollinated by insects, over a million people a year die from insect-borne diseases, and 20% of the world's crops are lost to insect attack. Insects are becoming resistant to many of our most useful insecticides, and few new ones have been brought to market in the last decade. An improved understanding of what makes insects so successful (in terms of species, they are the dominant life form on earth!) is thus vital in allowing us to find new, selective ways of eliminating harmful pests. Many of the most harmful insects (biting flies and mosquito vectors of disease, and crop-destroying caterpillars) have a specialization that is unique in biology; they run part of their guts at extraordinarily alkaline pH, as high as 12. If we can find out how this high pH is generated, we have a unique, selective target that allows us to attack harmful insects selectively. Our strategy is to identify genes that are expressed at high levels in the high-pH regions of the guts of the malaria and yellow fever mosquitoes, and the Bombyx silkworm caterpillar. Such genes will then be knocked out, either in these species directly, or in Drosophila (the fruit fly), a related insect for which genetic tools are particularly powerful. If gut pH is knocked down by such intervention, then we will have identified potential target genes for the development of new insecticides.

Insects destroy around 20% of the world's crops, and are vectors for diseases that kill over a million people every year. Widespread insecticide resistance and a shortage of new insecticides mandates the search for novel targets. The larvae of two of the most destructive Orders (Lepidoptera and Diptera), run their midguts at exceptionally high pH (10-12), far in excess of anything encountered in vertebrates. The project seeks to elucidate the mechanism of this alkalinisation, both for basic science reasons, and because this unique process could be targeted for the development of new, more selective (i.e. 'greener') insecticides. The strategy is to identify genes that are selectively enriched in alkalinizing regions of the alimentary canals of three species of insect representative of these Orders (Bombyx mori, Lepidoptera; Anopheles gambiae, Diptera; and Drosophila melanogaster, Diptera), and to study the impact of their knockdown on the alkalinizing ability of the midgut. The results will not only provide the most detailed insights yet into a critical and extreme transport process, but will allow us to start to develop assays for the future development of insecticides.

The proposal is framed with impact in mind. Academic: - we will be producing highly trained staff for the academic or industrial market. This extends beyond the staff directly employed on the project, to other members of the lab, including undergraduate project students. - We will be producing valuable, cross-species, rich expression datasets, of broad interest to those engaged in study of insect biology, pest control or comparative physiology - We will be advancing knowledge of ion transport, and of extreme biology Economic: - We will develop a model for the generation of uniquely high pH, and in doing so provide information that could lead to improved and selective control of insect pests. This is critically important at a time when new insecticides are slow coming to market, and insects are becoming resistant to those that already exist. Societal: - If we are successful, we will have taken steps towards genuinely novel insect control techniques. This will result in improved health and wealth worldwide for populations limited by the activities of pest insects. - It will increase our attractiveness for further inward investment from the agrochemical industry, leading to more skilled job creation and training, and further dialogues with key industrial partners. - At a general level, extreme biology captures the public imagination. Press releases such as 'pH 12 Achilles' heel inside key pest species', and 'the quest for greener insecticides', should trigger great (positive) press interest.