REGULATORY NETWORK CONTROLLING OVULE DEVELOPMENT IN Arabidopsis thaliana

In flowering plants ovules develop as lateral organ from the placenta and, once fertilized, give rise to seeds. My Ph.D. was mainly focused on the identification of the mechanisms controlling ovule number and development in Arabidopsis thaliana. AINTEGUMENTA (ANT), CUP-SHAPED COTYLEDON 1 (CUC1) and CUC2 are involved in ovule primordia initiation, since ant single and cuc1 cuc2 double mutant produce fewer ovule compared to wild type. Through the contemporary silencing of ANT, CUC1 and CUC2 we showed that these genes have additive roles in the determination of ovule number. Among all the developmental processes in which hormones are involved, their role in ovule primordia formation have been proposed for auxin and cytokinins. We show that CUC1 and CUC2 are required for correct auxin transport and that they, together with ANT are direct target of MP, a member of AUXIN RESPONSIVE FACTOR (ARF) family. Interestingly we saw that cytokinin treatments restore ovule number defects in our mutants increasing the expression of PINFORMED1 (PIN1), an auxin efflux carrier. Once the primordium is formed, the three MADS box transcription factors SEEDSTICK (STK), SHATTERPROOF1 (SHP1), and SHP2 redundantly regulate ovule development and, together with the SEPALLATA proteins determine ovule identity. I have contributed to the characterization of VERDANDI (VDD), the first direct target of the Arabidopsis ovule identity complex.