AtSUC1 ROOT EXPRESSION AND SUCROSE RESPONSE LEADING TO ANTHOCYANIN ACCUMULATION

Abstract

Previous research indicated that AtSUC1 root expression is controlled by intragenic sequences. The 5’ upstream region (promoter) of AtSUC1 directs pollen and trichome expression, but not root expression. However, the whole AtSUC1 gene can drive root expression and sucrose-induced root expression. Here I show that root expression of AtSUC1 is controlled by the interaction between the promoter and its two short introns. Deletion of either intron from whole-gene-GUS constructs resulted in no root expression, showing that both introns are required. The two introns in tandem, fused to GUS, produce high constitutive expression throughout the vegetative parts of the plant. When combined with the promoter, the expression driven by the introns is reduced and localized to the roots. AtSUC1 expression is also induced by exogenous sucrose, and AtSUC1 is also required for sucrose-induced anthocyanins (Sivitz et al., 2008). Anthocyanin accumulation due to high sucrose was lesser in the AtSUC1 mutant compared to Col-0 wild type. A whole-gene-GUS construct expressing a non-functional AtSUC1 (D152N) mutant, that is transport inactive, was defective in sucrose-induced AtSUC1 expression and anthocyanins accumulation when expressed in an atsuc1-null background. The results indicated that sucrose uptake via AtSUC1 is required for sucrose-induced AtSUC1 expression and anthocyanin accumulation, and that the site for sucrose detection is intracellular.