Abstract

Grafting is a widely used technique to improve crop yield. However, thus far, grafting has had limited success in improving tomato fruit quality and shelf life. One of the main bottlenecks in tomato grafting is the lack of knowledge of the molecules that could cross the graft junction and of their possible effects. Our hypothesis is that the combination of two genetically different plants by grafting can increase the diversity of the RNA molecules available for both partners. This combined RNA pool may affect gene expression in both scion and rootstock, and therefore unlock interesting phenotypic variability.

Small RNAs (sRNAs) are master regulators of gene expression which are able to travel long distance, mainly from source to sink, through plasmodesmata. Using tomato as a model, our aim is to investigate if endogenous sRNAs produced in the leaves of the graft (scion) can travel to the roots (rootstock). We will also investigate if mobile sRNAs can trigger changes in gene expression in the recipient tissue at transcriptional or post-transcriptional level.

Fruits can also be considered as carbon sinks, so an interesting aspect to explore would be whether sRNAs can also move to reproductive tissues, and if they have an effect on them. Most of the sRNAs found to be mobile are 24nt long and are known to be mainly involved in regulation of gene expression at transcriptional level by modification of the DNA methylation state. We want to explore the potential of mobile sRNAs as a tool to modify the expression of critical genes involved in fruit ripening and as a source of phenotypic variability that could have an impact in crop improvement.