Reciprocal grafting reveals the role of gibberellins in tomato root-shoot communication

Gibberellins (GAs) serve a multitude of functions in the regulation of processes associated with plant growth and development. The GA demand of an organ can be met through long-range transport from the site of synthesis. To examine the impact of altered GA biosynthesis on metabolism and growth, we performed reciprocal grafts of wild-type (WT; Solanum lycopersicum L.) and mutants exhibiting varying degrees of GA-deficiency (gib lines). The relative growth rate, based on plant height and specific leaf area, of the gib scions demonstrated partial recovery upon grafting to a WT rootstock. In contrast, the WT scion demonstrated recovery of root biomass and the root/shoot ratio in plants with gib rootstocks. Although the majority of free amino acids accumulated and negatively affected root growth of the WT rootstock, while the levels of organic acids and sugars were reduced. Increased levels of sugars and decreased levels of branched-chain amino acids in the roots of gib rootstock suggested that were the main carbon source to sustain the root growth. The multivariate analysis demonstrated growth and metabolism adjustments of the WT rootstock to supply the higher GA demand of the gib scions. In contrast, the WT scion displayed relatively minor metabolic alterations to support high rates of root growth and a reduced GA demand by the gib rootstocks. In this context, the strategic use of grafting between WT plants and GA-deficient mutants offers a viable approach to boosting agricultural productivity and strengthening plant resilience against abiotic stresses, providing an innovative alternative for sustainable crop management under challenging environmental conditions.