Land plants constitute a significant part of the world’s biomass and the human diet. The transition of plants to a land-based habitat led to profound developmental innovations. A major change was the formation of a sexual-based reproductive system. In basal land-plant linages, the haploid-gametophytic phase dominates the life cycle. In later linages the diploid-sporophytic phase took a more prominent role. This switch involved the elaboration of an embryo-based reproductive system. However, there is a significant gap in our understanding of the evolutionary, genetic and developmental mechanisms that enabled the formation of a sexual reproductive system. We hypothesize that embryo evolution entailed two key consecutive events: 1. Cell proliferation and growth following fertilization and prior to meiosis, which generates the sporophyte. 2. Specification of a subset of cells as sporogenous cells, which will generate the spores. Based on published work and recent data from the host lab, we propose that the first step involves class I KNOTTED1-like homeobox (KNOX1), and the second, class III Homeodomain-Leucine Zipper (C3HDZ). In the proposed research, we aim to use the basal land plants to 1. characterize the role of KNOX1 genes in sporophyte formation and 2. Identify regulators of sporogenous formation by identifying C3HDZ targets and determine their role in sporogenous specification. The proposed research is expected to elucidate the molecular network underlying reproductive development of land plants and its evolution. This may unravel basic principles of developmental innovations that enable the evolution of land plants and the conquest of novel habitat. This postdoctoral fellowship will provide me with an opportunity to be trained in the field of evolutionary-developmental biology and to achieve my future goals as an independent scientist.
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