A cytological and molecular approach towards the understanding of dichotomous spermatogenesis in gypsy moth (Lymantria dispar)

A balanced reduction of the genome at meiosis requires the proper chromosome metabolism during the prolonged prophase stage. The dichotomous meiotic programs (eupyrene and apyrene) of male gypsy moth have enormous potential as a tool for studying mechanisms responsible for chromosome pairing, synapsis, and segregation. While there have been a century of reports cytologically cataloguing the apyrene phenomena in hundreds of Lepidoptera, there does not exist a model that mechanistically accounts for the observations. With the advance of technology and breakthroughs in meiotic research, we undertook the task of systematically dissecting the events of apyrene development and advancing a viable hypothesis. ^ I began my search for a mechanistic theory of dichotomous meiosis in gypsy moth by first carefully studying their chromosome structure and behavior cytologically. This study provided novel observations about the events of prophase I during apyrene development: (1) early pairing is disrupted, (2) chromosomes precociously condense, and (3) univalents are formed at mid-prophase I. Through this work I have proposed a hypothesis stating that the apyrene trigger disrupts proper cytoskeletal dynamics early in prophase I, accounting for the pleiotropic effects associated with this meiotic program. We have identified the 3′ end of a kinesin-like gene (ldklp1) that shares homology to proteins involved in microtubule dynamics. The expression pattern of this gene suggests that it is meiotic specific. Furthermore, transcript levels of ldklp1 appear reduced in apyrene tissue. Diminished ldklp1 expression in apyrene spermatocytes could be a contributing factor to induction of apyrene development. Thus, we have created an entrez into dichotomous sperm production of Lepidoptera by providing a testable hypothesis. This work has furthered the understanding of meiosis in Lepidoptera, and meiosis in general, by contributing new observations, theories, and reagents available for future investigations.