Making of a flight appendage: an evolutionary perspective

       
ABSTRACT:
        Insects are the first to evolve flight appendages. Most insects have four wings (all directly contribute to the flight), while beetles and flies have only one pair of wings. In beetles, forewing is modified into thick protective organ called elytra. In the fruitfly Drosophila, the hindwing is modified into haltere, which helps in flying and maneuvering by functioning as a gyroscope. Except in few early insect groups, all four-winged insects too show differences in the forewing and hindwing morphology.

	In Drosophila, the differential development of wing and haltere is dependent on the function of Ultrabithorax (Ubx), a member of Hox family of transcription factors (transcription factors are those proteins which regulate the temporal and spatial expression of proteins encoded by other genes –latter genes are often referred to as target genes). A major focus in the lab is to understand the mechanism by which Ubx suppresses wing fate and specifies haltere development. Interestingly, Ubx protein has not evolved amongst the diverse insect groups suggesting that changes in the regulatory regions of targets of Ubx could be the driving force in modulating differences between forewing and hingwing morphology. Recently, we have initiated a study on the evolution of diversity in number, size and shape in insect wings by comparing targets of Ubx in different insect species such as Apis, Bombyx, Tribolium and Drosophila.