Title: DNA methylation in fleshy fruits: from tomato to grape
Speaker: Dr. Philippe Gallusc, Université de Bordeaux
Day/Date: Sunday/ April 8th, 2018
Host PI: Prof. Zhaobo Lang
Venue: PSC Auditorium
Epigenetic refers to heritable changes in chromatin organization, which may lead to modifications in gene expression but the underlying genomic DNA sequence remains unchanged. DNA methylation occurs on the 5th carbon of cytosine (5mC). This major epigenetic mark is involved in the control of gene expression and transposon mobility. Studies in Arabidopsis and other plants, have now demonstrated the relevance of epigenetic mechanisms in the control of plant developmental processes and their potential impact on traits of agronomical interest such as flowering time. Recently the distribution of 5mC over the tomato genome was shown to vary during fruit ripening suggesting that fruit development not only relies on hormones and genetic factors, but also on epigenetic regulations.
We have now shown that the balance between active DNA demethylation and methylation is critically important to tomato fruit development. We have generated various tomato lines that are impaired in DNA methylation (MET) or demethylation (DML). Metabolomics and RNA seq analysis were performed indicating that several aspects of fruit ripening are inhibited in fruits of DML lines. Inhibition of fruit ripening is due to the hypermethylation and repression of the expression of genes encoding ripening transcription factors and rate-limiting enzymes of important metabolic pathway. Inversely MET RNAi lines develop small fruits without clear alteration of fruit ripening, although plant development is severally impaired. Interestingly, whereas active DNA demethylation is critically important to tomato fruit ripening control, preliminary analysis of grape fruit is not consistent with a similar role in this plant. Hence, although DNA methylation appears important in both grape and tomato fruits, their function likely differs.