Transcriptome dynamics at theArabidopsisgraft junction reveal an inter-tissue recognition mechanism that activates vascular regeneration

Abstract

35 36The ability for cut tissues to join together and form a chimeric organism is a 37 remarkable property of many plants, however, grafting is poorly characterized at the 38 molecular level. To better understand this process we monitored genome-wide 39 temporal and spatial gene expression changes in grafted Arabidopsis thaliana 40 hypocotyls. Tissues above and below the graft rapidly developed an asymmetry such 41 that many genes were more highly expressed on one side than the other. This 42 asymmetry correlated with sugar responsive genes and we observed an accumulation 43 of starch above the graft that decreased along with asymmetry once the sugar-44 transporting vascular tissues reconnected. Despite the initial starvation response 45 below the graft, many genes associated with vascular formation were rapidly 46 activated in grafted tissues but not in cut and separated tissues indicating that a 47 recognition mechanism activated that was independent of functional vascular 48 connections. Auxin which is transported cell-to-cell, had a rapidly elevated response 49 that was symmetric, suggesting that auxin was perceived by the root within hours of 50 tissue attachment to activate the vascular regeneration process. A subset of genes 51 were expressed only in grafted tissues, indicating that wound healing proceeded via 52 different mechanisms depending on the presence or absence of adjoining tissues. Such 53 a recognition process could have broader relevance for tissue regeneration, inter-54

Grafting alters tomato transcriptome and enhances tolerance to an airborne virus infection

“…Plants perceive grafting as a considerable stress 22 , which, in this study, led to the differential expression of 1,991 unique genes corresponding to about 5.88% of the 33,810 total genes annotated in tomato genome. This number seems congruent with the alteration of 8% of the total genes annotated in Arabidopsis thaliana after the mechanical graft wounding 51 and with a high degree of overlapping among genes responsive to wound, abiotic stress and pathogen attack 40,51 , this study. Plants also perceive viral infection but as a different stress, which activates a multiplicity of concomitant and interrelated defense responses and viral counter-defense strategies like the suppression of RNA silencing 39,43,52 .…”

The Role of Grafting in the Resistance of Tomato to Viruses

“…In our study, the graft wound induced 1991 unique DEGs, which accounted for the 5.88% of the total genes (33,810) annotated in tomato genome (Solyc). This percentage was close to the 8% DEGs of the total genes annotated in A. thaliana involved in plant wound healing process [ 89 , 90 ]. Most of the graft wound responsive DEGs encoded signal molecules that overlapped their role also in response to abiotic stress and pathogen attack [ 64 , 87 , 90 , 91 ].…”

Micrografting device for testing systemic signaling in Arabidopsis

“…The chip did not show autofluorescence at the graft junction (Figure 3f). Tissue reconstruction at the graft junction involves phytohormones, the wounding response and vasculature development (Yin et al, 2012;Matsuoka et al, 2016;Melnyk et al, 2018). Several fluorescent reporter lines for these phenomena are available, such as DR5 promoter-driven fluorescent proteins (Otten-schl€ ager et al, 2003) and the R2D2 reporter (Liao et al, 2015) for the auxin response, WIND1p::GFP (Iwase et al, 2011) for the wounding response, and CALS7p::H2B:YFP (Furuta et al, 2014) and SEOR1p::SEOR1:YFP (Froelich et al, 2011) for vasculature development.…”