Acquisition of a potential marker for insect transformation: isolation of a novel alcohol dehydrogenase gene from Bactrocera oleae by functional complementation in yeast

The alcohol dehydrogenase genes make up one of the best studied gene famili es in Drosophila, both in terms of expression and evolution. Moreover, alco hol dehydrogenase genes constitute potential versatile markers in insect tr ansformation experiments. However, due to their rapid evolution, these gene s cannot be cloned from other insect genera by DNA hybridization or PCR-bas ed strategies. We have therefore explored an alternative strategy: cloning by functional complementation of appropriate yeast mutants. Here we report that two alcohol dehydrogenase genes from the medfly Ceratitis capitata can functionally replace the yeast enzymes, even though the medfly and yeast g enes have evolved independently, acquiring their enzymatic function converg ently. Using this method, we have cloned an alcohol dehydrogenase gene from the olive pest Bactrocera oleae. We conclude that functional complementati on in yeast can be used to clone alcohol dehydrogenase genes that are unrel ated in sequence to those of yeast, thus providing a powerful tool for isol ation of dominant insect transformation marker genes.