Epigenetic bases of grafting-induced vigour in eggplant [RNA-Seq]

In horticulture, grafting is a popular technique used to combine positive features of two different plants, obtained by joining a scion (generally the part above the ground) onto a rootstock (constituted by the stem and roots). Despite its wide-use, the biological mechanisms driving rootstock-induced alterations of the scion phenotype are not fully understood. Given that epigenetics is an important component of distance signalling in plants, we investigated the genome wide changes in the DNA methylation induced in eggplants grafted onto two interspecific rootstocks commercially used to induce scion vigour, compared to self-grafted plants. We found that vigour was associated to a specific change in scion gene expression and a genome wide hypo-methylation in CHH context. Interestingly, this hypomethylation correlated with downregulation of younger and potentially more active LTR retrotransposons. Our data indicate that graft-induced epigenetics modifications are associated to both physiological and molecular phenotypes in plants, and suggest that rootstocks can induce vigour by reducing DNA methylation in the scion genome, similarly to what observed in some heterotic hybrids. Transcriptional profile of 2 wild type Solanum melongena plants, and two replicates of S. melongena scions grafted on S. melongena (self graft), Solanum torvum and Solanum lycopersicum (var. Emperador).