Evolutionary convergence in duplicative transposition and subfunctionalization of the male fertility gene kl-2 in drosophilids

Abstract

Subfunctionalization is considered the most frequent model for maintaining gene duplications, being the main source of evolutionary novelties through the emergence of new genes. In this model, each copy goes to specialize in part of the original gene's functions. Although predicted, there are few cases of convergent subfunctionalization described, where a duplicated gene in different groups suffers the same subfunctionalization's selective pressures. In this project, we propose a detailed study of the case of kl-2 gene subfunctionalization. This gene is associated with sperm flagellar movement in fruit flies of genus Drosophila, being originally in an autosome and having been transposed to the Y chromosome in the ancestor of the genus, leaving an autosomal copy in its original position: CG9068, which has been reduced in size, encoding only the first domain of the original protein. In parallel, this same gene has undergone duplicative transposition in another branch of drosophilids, in the species Phortica variegata. In this second case, the autosomal copy suffered a similar reduction in size observed in CG9068, in a possible case of convergent subfunctionalization, something not yet described in Drosophila. To confirm the subfunctionalization scenario, we will investigate, through RT-PCR, RNA-Seq and knockout lines, the function and expression patterns of the CG9068 gene - unknown at the moment - and the kl-2 gene in Drosophila and its outgroups in Drosophilidae family, including the species Rhinoleucophenga americana, which has the autosomal gene in its ancestral position, not duplicated or subfunctionalized. In the subfunctionalization hypothesis, we predict that the ancestral gene fulfills the functions and expression patterns of its subfunctionalized copies, which have evolved specialization. (AU)