Failure to Burrow and Tunnel Reveals Roles forﾠjim lovellﾠin the Growth and Endoreplication of the Drosophila Larval Tracheae

The Drosophila protein Jim Lovell (Lov) is a putative transcription factor of the BTB/POZ (Bric- a-Brac/Tramtrack/Broad/ﾠPox virus andﾠZinc finger) domain class that is expressed in many elements of the developing larval nervous system. It has roles in innate behaviors such as larval locomotion and adult courtship. In performing tissue-specific knockdown with the Gal4-UAS system we identified a new behavioral phenotype forﾠlov: larvae failed to burrow into their food during their growth phase and then failed to tunnel into an agarose substratum during their wandering phase. We determined that these phenotypes originate in a previously unrecognized role forﾠlovﾠin the tracheae. By using tracheal-specific Gal4 lines, Lov immunolocalization and aﾠlovﾠenhancer trap line, we established thatﾠlovﾠis normally expressed in the tracheae from late in embryogenesis through larval life. Using an assay that monitors food burrowing, substrate tunneling and death we showed thatﾠlovﾠtracheal knockdown results in tracheal fluid-filling, producing hypoxia that activates the aberrant behaviors and inhibits development. We investigated the role ofﾠlovﾠin the tracheae that initiates this sequence of events. We discovered that whenﾠlovﾠlevels are reduced, the tracheal cells are smaller, more numerous and show lower levels of endopolyploidization. Together our findings indicate that Lov is necessary for tracheal endoreplicative growth and that its loss in this tissue causes loss of tracheal integrity resulting in chronic hypoxia and abnormal burrowing and tunneling behavior