Postharvest changes in LIN5-down-regulated plants suggest a role for sugar deficiency in cuticle metabolism during ripening.

The cell wall invertase gene (LIN5) was reported to be a key enzyme influencing sugar uptake of tomato (Solanum lycopersicum) fruit. It was additionally revealed to be a key regulator of total soluble solids content in fruit as well as for reproductive development, being mainly involved in flower development, early fruit and seed development but also in ripening. Here, we demonstrate that silencing of the LIN5 gene promotes changes affecting fruit cuticle development which has a direct effect on postharvest properties. Transformants were characterized by reduced transpirational water loss in mature fruits accompanied by several other changes in the cuticle. Quantitative chemical composition, coupled with microscopy of isolated cuticle fruits revealed that the cuticle of the transformants were characterized by an increase of the thickness as well as significant increase in the content of cuticle components (cutin, phenolic compounds, and waxes). Furthermore, detailed analysis of the waxes revealed that the transformants displayed changes in waxes composition, showing higher levels of n-alkanes and triterpenoids which can shift the proportion of crystalline and amorphous waxes and change the water flux through the cuticle. Expression of the genes involved in cuticle biosynthesis indicated that LIN5 influences the biosynthesis of components of the cuticle, indicating that this process is coupled to sugar uploading via a mechanism which links carbon supply with the capacity for fruit expansion.