Pre-harvest water deficit (PHWD) plays an important role in sugar accumulation of citrus fruit. However, the mechanism is not known well. Here, it was confirmed that PHWD promoted sucrose accumulation of citrus fruit, but had limited effect on fructose, glucose and total acid. A sucrose transporter, CsSUT1, which localizes to the plasma membrane, was demonstrated to function in sucrose transport induced by PHWD. Compared to wild-type, CsSUT1 overexpression in citrus calli stimulated sucrose, fructose and glucose accumulation, while its silencing in juice sacs reduced sucrose accumulation. Increased sugar accumulation in transgenic lines enhanced plant drought tolerance, and resulted in decreased electrolyte leakage, malondialdehyde and hydrogen peroxide contents, as well as increased superoxide dismutase activity and proline contents. An abscisic acid (ABA)-responsive transcription factor, CsABF3, was found with a same expression pattern with CsSUT1 under PHWD. Yeast one-hybrid, electrophoretic mobility shift assay and dual-luciferase assays all revealed that CsABF3 directly...

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