Cells expressing Desiccate are essential for morphogenesis of labial sensilla in Drosophila melanogaster adults

We recently discovered a new gene, Desiccate (Desi), that is expressed in the epidermis and protects larvae from desiccation stress in Drosophila melanogaster. In the present study, we found that taste organs express more Desi than the epidermis both in larvae and adults. Green fluorescent protein (GFP) expression in larvae under the direction of a Desi promoter-Gal4 line containing the 1,010-bp 5' flanking region of Desi produced no signal in the epidermis but strong signals in cells of the larval gustatory sense organs, indicating that this driver works specifically in the gustatory organs. In adults, GFP expression was also observed in basal cells of sensilla on labella, tarsi and wings. More precise morphological analysis of GFP expression located its expression in the outer accessory cells rather than neurons of the labial sensilla. Although Desi knockdown or induction of cell death in Desi-expressing cells did not change the morphological or physiological characters of the larvae, larvae lacking Desi-expressing cells failed to metamorphose normally, and all of them died inside puparia. Dying pharate adults were found to lack all labial sensilla. The proneural genes Achaete and Scute, which are involved in the development of the adult central and peripheral nervous system, were normally expressed in the pupae lacking Desi-expressing cells. These results suggested that the lack of Desi-expressing cells makes it impossible to produce outer accessory cells for development of the sensilla, thereby signifying that cells expressing Desi are essential for normal morphogenesis of the labial sensilla in Drosophila adults.