SRSR · Deciphering small RNA mechanisms during sexual reproduction in Arabidopsis

Sexual reproduction is a key moment in many organisms’ life cycle that ensures the proper inheritance of traits and also allows adaptation. In both plants and metazoans, reproduction entails the complex coordination of gene expression between the different tissues involved. For example, intricate modifications of epigenetic landscapes occur during and around fertilzation to ensure zygotic totipotency while maintaining genome integrity. In recent years, key connections have been established between silencing small (s)RNA and reproduction with the discovery of piwi-associated small RNAs (piRNAs) in Drosophila. In the model plant Arabidopsis, a clear link exists between silencing sRNAs and the chromatin via de novo DNA methylation and Histone tail modifications, in a process referred to as RdDM. However, almost nothing is known about the involvement of sRNAs in the reproductive process. This project aims at filling this gap by studying sRNA-mediated mechanisms in tissues before and after fertilisation, i.e. in the plant germline and in the zygote. This proposal outlines a series of interdisciplinary and mutually reinforcing experiments to 1) Characterize the silencing machinery available during sexual reproduction in Arabidopsis; 2) Establish an unbiased developmental map of reproduction-associated sRNA; and 3) study the possible movement of sRNAs between and toward reproductive organs. The results are expected to shed a completely new light on plant reproduction and, more generally, might unravel novel sRNA-based regulations. The proposed project also has profound implications in agriculture as it may elucidate aspects of the poorly understood mechanisms underpinning hybrid vigour as well as intra- and inter-species compatibility. Finally, knowledge on cell biology, imaging and Arabidopsis reproduction biology implemented during the proposed project will contribute to European excellence and competitiveness in the field.