A sucrose non-fermenting-1-related protein kinase 1 gene from potato, StSnRK1, regulates carbohydrate metabolism in transgenic tobacco.

Sucrose non-fermenting-1-related protein kinase 1 (SnRK1) has been shown to play an essential role in regulating saccharide metabolism and starch biosynthesis of plant. The regulatory role of StSnRK1 from potato in regulating carbohydrate metabolism and starch accumulation has not been investigated. In this work, a cDNA encoding the SnRK1 protein, named StSnRK1, was isolated from potato. The open reading frame contained 1545 nucleotides encoding 514 amino acids. Subcellular localization analysis in onion epidermal cells indicated that StSnRK1 protein was localized to the nucleus. The coding region of StSnRK1 was cloned into a binary vector under the control of 35S promoter and then transformed into tobacco to obtain transgenic plants. Transgenic tobacco plants expressing StSnRK1 were shown to have a significant increased accumulation of starch content, as well as sucrose, glucose and fructose content. Real-time quantitative PCR analysis indicated that overexpression of StSnRK1 up-regulated the expression of sucrose synthase (NtSUS), ADP-glucose pyrophosphorylase (NtAGPase) and soluble starch synthase (NtSSS III) genes involved in starch biosynthesis in the transgenic plants. In contrast, the expression of sucrose phosphate synthase (NtSPS) gene was decreased in the transgenic plants. Meanwhile, enzymatic analyses indicated that the activities of major enzymes (SUS, AGPase and SSS) involved in the starch biosynthesis were enhanced, whereas SPS activity was decreased in the transgenic plants compared to the wild-type. These results suggest that the manipulation of StSnRK1 expression might be used for improving quality of plants in the future.