Phenolicsandcellwallremodellingin fruits of tomatooverexpressing GGP1gene

Tomato fruit ripening involves complex physiological processes, including the biosynthesis and degradation of cell wall components such as polysaccharides, phenolics, and proteoglycans, leading to fruit softening. In this study, we investigated how the overexpression of GDP-Lgalactose phosphorylase (GGP1)– a key gene in the Lgalactose-dependent ascorbate (Asc) biosynthesis pathway- under the control of two fruit-specific promoters, namely PPC- phosphoenolpyruvate carboxylase and PG– polygalacturonase, influences cell wall properties and phenolic profile. It was shown that GGP1 overexpression increases Asc content in ripening tomato fruit and upregulates genes associated with cell wall remodelling [1]. Here, we demonstrated that PPC-GGP1 and PG-GGP1 transgenic lines exhibited significant structural alterations in the fruit parenchyma compared to wild-type fruits, particularly a disruption of cell wall composition and organisation [2]. These included modifications in spatial distribution and chemical composition of homogalacturonans and arabinogalactans, as well as changes in the pectin methylation degree. Alongside with reduced content of free chalconaringenin, p-coumaric and protocatechuic acids, the amount of cell wall-bound p-coumaric acid and the corresponding monolignol, p-coumaryl alcohol, was higher in the transgenic fruits. These findings highlight a metabolic interplay between Asc biosynthesis and cell wall remodelling, with potential implications for postharvest fruit quality and storage.