Cloning and characterization of a carbohydrate metabolism-associated gene IbSnRK1 from sweetpotato

- A carbohydrate metabolism-associated gene IbSnRK1 is cloned from sweetpotato.
- IbSnRK1 shows high identities with SnRK1 of other plants.
- Over-expression of IbSnRK1 gene increases soluble sugar and starch levels of transgenic tobacco plants.
- IbSnRK1 gene may play important roles in carbohydrate metabolism and starch biosynthesis.

Sucrose non-fermenting-1-related protein kinase-1 (SnRK1) plays an important role in plant carbohydrate metabolism and starch biosynthesis. In the present study, a SnRK1 gene, named IbSnRK1, was isolated from sweetpotato (cv. Lushu No. 3) by rapid amplification of cDNA ends (RACE). The open reading frame (ORF) contained 1515 nucleotides encoding 504 amino acids. The deduced amino acid sequence showed high identities with SnRK1 of other plants. Real-time quantitative PCR analysis revealed that the expression level of IbSnRK1 gene was significantly higher in leaves of Lushu No. 3 than in its stems and roots. The leaf photosynthetic rate of transgenic tobacco (cv. Wisconsin 38) plants over-expressing IbSnRK1 gene was significantly increased comparing with that of the wild-type. The activity of sucrose synthase (SS) and ADP-glucose pyrophosphorylase (AGPase) was increased by 11-28% and 30-92%, respectively, whereas the activity of sucrose phosphate synthase (SPS) was decreased by 27-42%. Sucrose, glucose, fructose and starch were found to be significantly more accumulated in transgenic tobacco plants than in the wild-type. These results suggest that IbSnRK1 gene plays important roles in carbohydrate metabolism and starch biosynthesis and may be applied for increasing soluble sugar and starch levels of sweetpotato in the future.