Global DNA methylation changes in Cucurbitaceae inter-species grafting

Grafting has been used to improve yield, fruit quality and disease resistance in a range of tree and vegetable species. The molecular mechanisms underpinning grafting responses have only recently started to be delineated. One of those mechanisms involves long distance transfer of genetic material from rootstock to scion alluding to an epigenetic component to the grafting process. In the research presented herein we extended published work on heritable changes in the DNA methylation pattern of Solanaceae scion genomes, in Cucurbitaceae inter-species grafting. Specifically, we examined global DNA methylation changes in scions of cucumber, melon and watermelon heterografted onto pumpkin rootstocks using MSAP analysis. We observed a significant increase of global DNA methylation in cucumber and melon scions pointing to an epigenetic effect in Cucurbitaceae heterografting. Exploitation of differential epigenetic marking in different rootstock-scion combinations could lead to development of epi-molecular markers for generation and selection of superior quality grafted vegetables.

嫁接（grafting）技术已被广泛应用于多种林木与蔬菜物种中，用于提升其产量、果实品质与抗病性。支撑嫁接响应的分子机制直至近年才得以厘清。其中一类机制涉及遗传物质从砧木（rootstock）向接穗（scion）的长距离转运，这暗示嫁接过程存在表观遗传（epigenetic）调控组分。本研究针对已发表的、关于葫芦科（Cucurbitaceae）种间嫁接场景下茄科（Solanaceae）接穗基因组DNA甲基化模式的可遗传变化的研究进行了拓展。具体而言，本研究采用MSAP分析，对以南瓜为砧木、经异源嫁接（heterografting）的黄瓜、甜瓜与西瓜接穗的全基因组DNA甲基化变化进行了检测。本研究观测到黄瓜与甜瓜接穗的全基因组DNA甲基化水平显著升高，这表明葫芦科异源嫁接过程存在表观遗传效应。针对不同砧木-接穗组合的差异表观遗传标记进行开发利用，有望催生可用于培育和筛选优质嫁接蔬菜的表观分子标记（epi-molecular markers）。