Reductions of endogenous gibberellin content impact fruit development and modify tomato fruit metabolism during ripening

Abstract

Gibberellins (GAs) play a crucial role in modulating developmental processes throughout the plant life cycle. Among the processes in which GAs are involved, they are of significance during the transition and maintenance of the reproductive meristem, as well as in allowing the floral organs development. GAs are also able to regulate, alongside with auxin and cytokinin, the initial processes of fruit development, most likely because they are responsible for both division and cell expansion. It is unknown whether fluctuations in the endogenous content of GAs impact fruit development and metabolism during ripening. To investigate these questions, tomato mutant plants deficient in GAs biosynthesis (gib3, moderately deficient; gib2, intermediate deficiency and gib1, extremely deficient in GA) were used. Notably, gib2 and gib1 mutants were characterized by a complete interruption of their reproductive development at the floral bud level. Although gib3 plants displayed a slightly delay in fruit development, at the end of fruit ripening both WT and gib3 fruits were highly similar. Little differences were found between WT and gib3 mutant plants during floral development and total fruit yield. We demonstrated that reduced GAs in gib3 mutant did not promote morphological modifications in fruits and relatively few metabolic changes were observed between genotypes during fruit ripening. Overall, typical metabolic changes, including increments in amino acids and soluble sugars coupled with reductions in starch, were observed during ripening. Collectively, we demonstrate that GAs plays a significant role on change vegetative to reproductive stage, as well as on the binging of set fruit.