Cofactor-dependent and -independent functions of Hox reveal two distinct evolutionary lineages of insect wing tissues

Insects wings qualify as novel structures and their origin is unknown. Recent work has found tissues serially homologous to the wing (named wing serial homologs, or WSHs) in the wingless body segments of Tribolium castaneum (red flour beetle), and here I investigate these tissues further. Hox genes control segmental identity along the body axis, and work with their cofactor complex, Hth/Exd. We propose that among the tissues identified to be WSHs, there are tissues that are Hox cofactor-dependent or -independent. We use RNAi techniques to target one of the cofactor genes (hth) and the Hox genes specific to each thoracic segment, in order to investigate this. We find that Hth/Exd are important in the formation of one of the WSHs in the thorax.