[Gene expression modulation is an evolutionary resource of adaptive alterations in the morphogenesis of insect limbs]

Hypomorphic mutations have been investigated of the genes spineless (ss), Distal-less (Dll), leg-arista-wing complex/TBP-related factor 2(lawc/Trf2), CG5017, and hsp 70 in order to explore the effects of their expression level on the formation of distal structures of antenna and legs of Drosophila melanogaster. We demonstrated the effect of the CG5017, hsp 70, Dll, and lawc gene transcription level on phenotypic manifestation of the ss gene mutation and the involvement of these genes into morphogenesis regulation of Drosophila melanogaster limbs. The total decrease in the level of the CG5017, hsp 70, Dll, and laws gene expression level was shown to promote a loss of the segmented pattern of distal structures of legs and antennae and a reversion of Drosophila limb morphogenesis to the evolutionarily earlier progenitors of insects. A hypothesis is proposed considering limb morphogenesis of insects as an evolutionary ancient process of formation of amorphous-crystal chitin structures with catalytically modifying participation of gene expression products.