Physiol Mol Biol Plants 2025 Nov 11;3111:1963-1978. doi: 10.1007/s12298-025-01668-1.

Molecular characterization and expression of sucrose transporters (SUTs) in response to water deficit in tomato and effects of Rin and Nr mutations.

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UNLABELLED: This study investigated the molecular features and gene expression of tomato sucrose transporters (SUTs) in response to water deficit and the effects of ripening mutations rin and Nr. In silico analyses were carried out to characterize the amino acid sequences, conserved domains and gene structure of the SlSUTs. Wild-type (WT) and two near isogenic lines (NILs) of Micro-Tom harbouring the rin and Nr mutations were subjected to control and water deficit treatments and physiological and molecular analyses were carried out, including leaf gas exchange, antioxidant enzyme activity, soluble sugars concentration, and SUT gene expression in different source-sink organs. The results showed that the SlSUT genes are structurally conserved but variable in sequences, suggesting functional specialization within this gene family. Plant phenotyping revealed a metabolic adjustment of tomato plants grown under water deficit, including an increase in the concentration of soluble sugars in fruits and leaves. SlSUT1 and SlSUT4 were responsive to water deficit mainly in leaves and fruits, with such responses being annulled in leaves by the rin mutation. In addition, SlSUT4 was down-regulated by water deficit in roots, irrespective of the genotype, and showed a co-regulated expression with SlETR2. SlSUT2 was also induced by water-deficit in leaves and fruits, with the Nr mutation making it responsive also in roots. Collectively, these data indicate that SlSUT genes are structurally conserved but functionally distinct, exhibiting a differentially regulated expression in response to water deficit and RIN and Nr signaling in different source-sink organs. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-025-01668-1.

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