Epigenetic contribution to grafting induced vigour in Solanaceous plants

嫁接是一种古老的用于提高植物产量的农艺方法，自4000多年前就被用来提高植物的产量，包括将两种植物物理连接在一起，通常称为砧木和接穗。虽然嫁接是传统上应用于树木的，但最近它在商业草本植物中的使用越来越普遍，特别是茄科植物。这是因为砧木既能抵抗几种病原菌，又能增加植物的活力，从而提高植物产量。虽然提供病原菌抗性的过程已经得到了很好的描述，并且通常与砧木的内在特性(例如对地上病原菌的自然免疫力)有关，但植物活力的增强意味着接穗结构的间接改变是由砧木诱导的，所涉及的机制在很大程度上仍不清楚。植物活力与表观遗传修饰有关，差异甲基化基因(外膜)可以影响具有相同DNA基因组序列的植物的表型。此外，在模式植物上进行的实验表明，小RNA分子(SRNAs)可以从砧木系统地移动通过植物维管组织，并在接穗中直接进行DNA甲基化修饰。首先，获得嫁接在不同砧木上的番茄和茄子接穗的DNA甲基化图谱，并研究基因组甲基化与植物活力的差异。其次，对通过嫁接结合传递活力信号的表观遗传学机制进行表征。这一目标将通过对关键表观遗传因素中突变的番茄接穗的表型进行评分来实现。最后，使用异种嫁接的植物组合来筛选和表征从砧木到接穗的可能潜在地指导表观遗传变化的砧木特有的小RNA分子。

Grafting is a long-standing agronomical method used to improve plants production since more than 4000 years ago, consisting in physically joining two plants together, generally referred as rootstock and scion. While grafting is traditional applied to trees, recently its use is becoming increasingly popular in commercial herbaceous crops, and Solanaceous plants in particular. This is because rootstocks can both provide resistance to several pathogens and increase plant vigour, improving plant production. While the processes providing pathogen resistance are well described and generally associated to intrinsic proprieties of the rootstock (e.g. natural immunity to pathogens in the ground), the enhanced plant vigour implies that indirect modifications of scion architecture are induced by the rootstock, and the underlined mechanisms are still largely unknown.Plant vigour has been associated to epigenetic modifications, and differentially methylated genes (epialelles) can affect phenotypes in plants with identical DNA genomic sequence. In addition, experiments performed on model plants demonstrated that small RNA molecules (sRNAs) can move systemically from rootstock through the plant vascular tissue, and direct DNA methylation modification in scions.The investigation aims to explore three key objectives. Firstly, to obtain the DNA methylation profile of tomato and eggplant scions grafted on different rootstocks, and investigate the differences in genome methylation associated to plant vigour. Secondly, to characterize the epigenetic mechanisms involved in the transmission of the vigour signal through the graft union. This objective will be achieve by scoring the phenotype of tomato scions mutated in key epigenetic factors. Lastly, use the hetero-grafted plant combinations to screen and characterize rootstock-specific small RNA molecules travelling from the rootstock to the scion which could potentially direct epigenetic changes.