MSc by Research: Defying Mendel’s laws: developing tools to understand the principles of epigenetic inheritance in tomato plants

About the Project

In plants, phenotypic innovation is not exclusively encoded inDNA sequences. Some heritable new traits are associated with modifications onthe DNA, such as DNA methylation. DNA methylation involves the binding of methyl groups to cytosines in the DNA molecule. High DNA methylation levels cause transcriptional gene silencing (TGS) and switch genes off. Because this type of regulation is independent of DNA sequences it is referred to as epigenetic.

In most cases DNA methylation is inherited in a Mendelian fashion. However, DNA methylation can be transferred between homologous alleles. This type of communication between alleles is referred as paramutation and it violates Mendel’s first law of segregation.

Recently, it was found that a DNA methyltransferase (CMT3) and Histone methyltransferase (KYP) are required to maintain paramutation in a model for paramutation in tomato (sulfurea) across generations1. However, the mechanisms underlying the establishment of paramutation remain poorly understood.

How can an epigenetic mark be transferred from one locus to the other in somatic cells after fertilization? To address this question, we hypothesize that proteins involved in the establishment of epigenetic marks might be involved in this process. These include proteins involved in generating small RNAs since in plants these RNA molecules initiate DNA methylation. In this project the student will design, carry out in vitro validation and generate constructs to knock-out proteins involved in sRNA generating pathways in tomato.

In addition, we recently found that cis regulatory regions might be required to establish paramutation (unpublished). How are these cis regulatory regions regulated and how do they affect paramutation? We hypothesize the DNA methylation status of cis regulatory regions affects paramutation at the sulfurea locus. To test the effect of these epigenetic marks the student will transiently transfect plant cells with DNA demethylases2 targeted at sulfureaand analyze its status. Once this transient system is established other hypotheses can be tested.

This project will employ genetics, biotechnology and molecular biology to shed light on one of the oldest and unsolved mysteries in plant genetics but also provide valuable technical expertise in crop science and biotechnology.

Our research community thrives on the diversity of students and staff which helps to make the University of Dundee a UK university of choice for postgraduate research. We welcome applications from all talented individuals and are committed to widening access to those who have the ability and potential to benefit from higher education.