Rootstocks Overexpressing and Improve Osmotic Stress Tolerance of Wild-Type Scion in Transgrafted Tobacco Plants.

In grafted plants, the movement of long-distance signals from rootstocks can modulate the development and function of the scion. To understand the mechanisms by which tolerant rootstocks improve scion responses to osmotic stress (OS) conditions, mRNA transport of osmotic responsive genes (ORGs) was evaluated in a tomato/potato heterograft system. In this system, was used as a rootstock and as a scion. We detected changes in the gene expression levels of 13 out of the 21 ORGs tested in the osmotically stressed plants; of these, only transcripts were transported across the graft union under both normal and OS conditions. Importantly, OS increased the abundance of transcripts in the tomato scion. To examine mRNA mobility in transgrafted plants, and genes representing the mobile and non-mobile transcripts, respectively, were overexpressed in tobacco (). The evaluation of transgenic tobacco plants indicated that overexpression of these genes enhanced the growth and improved the physiological status of transgenic plants growing under OS conditions induced by NaCl, mannitol and polyethylene glycol (PEG). We also found that transgenic tobacco rootstocks increased the OS tolerance of the WT-scion. Indeed, WT scions on transgenic rootstocks had higher ORGs transcript levels than their counterparts on non-transgenic rootstocks. However, neither nor transcripts were transported from the transgenic rootstock to the wild-type (WT) tobacco scion, suggesting that other long-distance signals downstream these transgenes could have moved across the graft union leading to OS tolerance. Overall, our results signify the importance of and as two anticipated candidates for the development of stress-resilient crops through transgrafting technology.