Sucrose distribution in peach fruit during development and role of three distinct sucrose transporters

The carbohydrate distribution is a complex system governed by several physiological processes, including phloem loading in the source leaf, long-distance translocation in the phloem, phloem unloading in sink organs, post-phloem transport and metabolism of imported sugars in sink cells. The pathway of phloem unloading and post-phloem transport has been analyzed in several sink organs, including fruits, but is not still elucidated in peach fruit. Therefore, aim of this work was to characterize the mechanism of phloem unloading and post-phloem transport in two different types of peach tissues (mesocarp and seed) using a specific fluorescent marker of phloem transport, the carboxyfluorescein diacetate (CFDA), and analyzing the role of different sucrose transporters. The availability of the complete sequence of peach genome, allowed the identification of genes encoding proteins involved in sucrose transport, and several approaches, such as Real-Time PCR, laser capture microdissection and in situ hybridization, have been adopted in order to analyze their transcriptional regulation during different stages of seed and fruit growth. Finally, SUT proteins have been functional characterized in heterologous system, and localized at subcellular level through expression of tag fused protein by transient transformation of Nicotiana benthamiana leaves mediated by agrobacterium tumefaciens.