Vitellogenesis is the most important process in oocyte maturation and has a pivotal role in insect reproduction.

In our model, the cockroach Blattella germanica, vitellogenin synthesis is produced in the fat body and regulated by Juvenile Hormone (JH). At the same time, JH acts on the ovary inducing the patency in the follicular epithelium and facilitating the uptake of vitellogenin by the oocyte through specific receptors. Our aim is to understand the mechanism of vitellogenin synthesis induced by JH and to elucidate the mechanisms regulating the expression of the involved receptors.

Oogenesis comprises the formation of the ovary, its capacitation in the preimaginal stages, the stages ofprevitellogenesis, vitellogenesis and chorion formation, the oviposition and the process of apoptosis in the remaining follicular epithelia.

Until now, ovarian maturation has been studied in detail only in the most modified species, like Drosophila melanogaster with meroistic ovaries and mainly regulated by ecdysone. We chose a panoistic model, B. germanica, to study ovarian maturation, focusing our research in oocyte capacitation and previtellogenesis, oocyte development in vitellogenesis, and chorion synthesis. Attention is also paid to the role of miRNA in regulating oogenesis.

In insects we can distinguish two types of ovaries: panoistic and meroistic. The panoistic type is more frequent among basal insects, whereas the meroistic type predominates in more modified groups, which suggest that the evolutionary transition was from panoistic to meroistic.

Our aim is to understand such transition and the work hypothesis is that some genes will be conserved in structure and function in panoistic and meroistic ovaries, whereas other genes will be specific of one of these types o will have different functions in the two ovarian types. The idea is to study the function of genes expressed in the ovary of B. germanica and to establish how many of these genes and functions are conserved in meroistic models. Data obtained might suggest functional scenarios underlaying the transition between the panoistic and the meroistic types, and would afford new light to understand the evolution of insect ovaries, in general.