Spatiotemporal changes in secondary metabolites during graft formation in grapevine reveal tissue-specific accumulation of metabolites in necrotic and callus tissues

Abstract

Grafting is widely used in horticulture, shortly after grafting, callus tissues appear at the graft interface and the vascular tissues of the scion and rootstock connect. The graft interface contains a complex mix of tissues, we hypothesized that each tissue have is own metabolic response to wounding/grafting and accumulate different metabolites at different rates. We made intact and wounded cuttings and grafts of grapevine, and then measured changes in bulk secondary metabolite concentration and used metabolite imaging to study tissue specific responses. We show that some metabolites rapidly accumulate in specific tissues after grafting, e.g. stilbenes accumulate in necrotic tissues surrounding mature xylem vessels and gradually oligomerize over time. We also observe that some metabolites accumulate in the newly formed callus tissue at the graft interface and identify genotype-specific responses. Here we reveal the spatiotemporal dynamics of metabolite changes occurring during graft union formation for the first time. The rapid accumulation of stilbenes in the tissues damaged during the grafting process could be a plant defence mechanism, as stilbenes have antioxidant and anti-fungal capacities. The increasing oligomerization of stilbenes often occurs in response to plant stresses (via unknown mechanisms), but it potentially increases antioxidant activity. Brief summarySecondary metabolites accumulate after wounding and grafting in plants yet we have limited knowledge of tissue specific accumulation patterns and temporal dynamics. We show that stilbenes accumulate specifically in necrotic tissues and oligomerize over the time, whereas other compounds accumulate in the newly formed callus tissues. This suggests that these compounds have different roles in wounding healing and grafting.