Cell-cell adhesion in plant grafting is facilitated by β-1,4-glucanases

Abstract

Plant grafting is conducted for vegetative propagation in plants, whereby a piece of living tissue is attached to another tissue through establishment of cell-cell adhesion. Plant grafting has a long history in agriculture and has been applied to improve crop traits for thousands of years1. Plant grafting has mostly relied on the natural ability of a plant for wound healing. However, the compatibility of cell-cell adhesion typically limits graft combinations to closely related species2-4, and the mechanism by which cell-cell adhesion of injured tissues is established is largely unknown. Here, we show that a subclade of {beta}-1,4-glucanases secreted into the extracellular region facilitates cell-cell adhesion near the graft interface. Nicotiana shows a propensity for cell-cell adhesion with a diverse range of angiosperms, including vegetables, fruit trees, and monocots, in which cell wall reconstruction was promoted in a similar manner to conventional intrafamily grafting5-7. Using transcriptomic approaches, we identified a specific clade of {beta}-1,4-glucanases that is upregulated during grafting in successful graft combinations but not in incompatible grafts and precedes graft adhesion in inter- and intrafamily grafts. Grafting was facilitated with an overexpressor of the {beta}-1,4-glucanase and, using Nicotiana stem as an interscion, we produced tomato fruits on rootstocks from other plant families. Our results demonstrate that the mechanism of cell-cell adhesion is partly conserved in plants and is a potential target to enhance plant grafting techniques.