Evolution and development of insect wings a comparative analysis of the genome wide targets of the hox protein ultrabithorax in bombyx mori apis mellifera and drosophila melanogaster

Abstract

Insects are the first animals to have acquired flight during evolution They represent the largest order with abundant species diversity in the animal kingdom The variety in body forms is also evident in the flight appendages of the various different insect groups which have remarkable diversity in the number and size of wings Most insects have four wings while beetles and flies have only one pair of wings In beetles the forewings are modified as thick protective cover called elytra and only hind wings perform the flight function In contrast in flies only the forewings perform the flight function while the hind wings are modified to a small club shaped balancing organ called haltere Except in few early insect groups they all show differences between forewing and hindwing morphology The insect body is divided into segments in which the development and fate of different organs is mainly controlled by a set of master control genes of the Hox complex The Hox genes are highly conserved across the animal kingdom and are the main players in generating morphological diversity along with body axis within an organism Suppression of wing fate and specification of haltere fate in Drosophila melanogaster by the Hox gene Ultrabithorax Ubx is a classic example of Hox regulation of serial homology which has served as a paradigm for understanding Hox gene function The differential development of wing and haltere constitutes a good genetic system to study cell fate determination at different levels such as growth cell shape size and its biochemical and physiological properties They also represent the evolutionary trend that has established the differences between fore and hindwings in insectsUbx which is required to specify haltere development in Drosophila is expressed in T3 segments during development of all insects studied so far Furthermore the Ubx protein itself has not evolved amongst the diverse insect groups although there are significant differences in Ubx sequences between Drosophila and crustacean A newline newline