Epigenetic bases of grafting-induced vigour in eggplant [Bisulfite-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. Examination of DNA methylation 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).

在园艺领域中，嫁接是一项广受欢迎的技术，通过将接穗（scion，通常指植物地上部分）接合到由茎与根系构成的砧木（rootstock）上，以整合两种不同植物的优良性状。尽管嫁接应用极为广泛，但驱动砧木诱导接穗表型改变的生物学机制仍未完全阐明。鉴于表观遗传学（epigenetics）是植物远距离信号传导的重要组成部分，本研究以自嫁接植株为对照，对嫁接于两种商用种间砧木以诱导接穗长势的茄子进行了分析，探究其接穗体内的全基因组DNA甲基化（DNA methylation）变化。研究发现，植株长势与接穗基因表达的特异性改变以及CHH序列背景下的全基因组低甲基化（hypo-methylation）密切相关。值得注意的是，这种低甲基化现象与较为年轻且潜在活性更强的LTR反转录转座子（LTR retrotransposons）的表达下调存在关联。本研究数据表明，嫁接诱导的表观遗传修饰与植物的生理及分子表型均存在关联，且提示砧木可通过降低接穗基因组的DNA甲基化水平诱导植株长势提升，这与部分杂种优势杂交种中观察到的现象一致。本研究对2株野生型茄子（Solanum melongena）植株，以及分别嫁接于茄子（自嫁接）、野茄（Solanum torvum）和番茄（Solanum lycopersicum，品种‘Emperador’）的2组重复茄子接穗的DNA甲基化水平进行了检测。