Evolution of molecular networks controlling the seed coat differentiation

Ginkgo biloba is an ancient gymnosperm increasingly studied not only for its active principles important in human medicine, but also from an evolutionary point of view. In this research thesis I have reported the results obtained by me and my collaborators during three years of research on the ovule development in Ginkgo biloba. The Ginkgo ovule is formed by the nucellus, in which the female gametophyte will form, and by one integument that protects and surrounds the nucellus. At maturity, the single ovule integument will differentiate into the seed coat which protects the embryo. So far, the main molecular mechanisms and genes responsible for ovule development and for the switch from ovule integument/s into seed coat have been studied in Arabidopsis thaliana and few more model angiosperms. We tried to understand and to better elucidate the mechanisms that regulate Ginkgo ovule development in order to provide a more inclusive representation of these processes across seed plants. Indeed, diversity within seed plants and within their ovule types is too high to be synthetically described through studies that only consider model angiosperms. During these three years a morphological atlas describing Ginkgo ovule development stages has been produced, and also several RNA sequencing on ovules at different stages and in different conditions have been performed. In particular, in order to characterize the crucial event of pollination, we have sequenced five stages of Ginkgo ovules around the pollination event, and then three post pollination stages of both pollinated and non-pollinated ovules. These analyses allowed us to describe accurately which are the main changes that Ginkgo ovules face during the crucial pollination time. In addition, I was also able to describe the early Ginkgo ovule development describing the expression domains of Ginkgo orthologs of key ovule regulatory genes widely studied in Arabidopsis. My Ph.D. project was part of a bigger project in which were involved also collaborators from the University of Milano and from the University of Cosenza, who also provided lot of data on Ginkgo and on Arabidopsis. All the produced data allowed a comparison between the two species and allowed a description of early and later Ginkgo ovule development stages. These data resulted into three publications, of which two strictly on Ginkgo biloba ovule development, and in a manuscript in preparation.