Sex in plants and the role of genomic imprinting
Yuri Stephan van Ekelenburg, Biosciences
Most flowering plants have sex to produce the next generation inside the seed. They have male and female sexual organs (the pollen and the ovule respectively), and inside these structures male and female germ cells are made. Seed development is initiated by a double fertilization event where the two sperm cells fertilize the egg cell and the central cell. After fertilization, the egg develops to form the diploid embryo, while the central cell forms the triploid endosperm. The endosperm surrounds the embryo and is the main regulator of the flow of nutrients in the seed. A phenomenon called genomic imprinting is an important epigenetic regulator of gene expression in endosperm development. In this process, gene expression occurs from only one of the parental alleles whereas the other allele is silenced.
What regulates genomic imprinting is not fully known, but there are several mechanisms reported to be responsible for genomic imprinting, including epigenetic regulation by histone and DNA methylation. Furthermore, it has been postulated that a process called RNA directed DNA Methylation (RdDM) also acts as a regulator of imprinting. RdDM is a mechanism in which non-coding RNA products are processed to 20–24 nt single stranded RNA. These small RNAs can bind to newly produced transcripts where it recruits a protein complex, which de novo methylates the closely located DNA region.
This PhD project aims to investigate the role of small RNAs in genomic imprinting.