ObjectiveCalvin cycle plays an important role in the photosyntheic process and strongly impacts the growth and development of plants.Previous studies have showed that expression level of sedoheptulose-1, 7-bisphosphatase (SBPase) gene is significantly up-regulated in the fast-growing hybrid poplar with the high photosynthetic rate in fast-growth phase, suggesting that the gene may plays a key role in the photosynthetic carbon fixation.

MethodIn order to further analyze the function of SBPase in photosynthetic efficiency and plant growth and development in woody plants, PdSBP gene was cloned from fast-growing hybrid Populus NE-19 (Populus nigra×(Populus deltoids×Populus nigra)).The 35S: PdSBP: GFP expression vector was constructed and transformed into Arabidopsis thaliana by Agrobacterium tumefaciens inflorescence infection. We used antibiotic selection, PCR identification and subcellular localization to successfully achieve the overexpressing PdSBPase Arabidopsis.

ResultUnder normal growth conditions, the leaf area, root length, and plant height of overexpressing plants were all better than those of wild type and mutant. Among them, the leaf area of transgenic plants was 1.79 times of the wild type and the root length was 1.93 times of the wild type. In comparison, the mutant had an obvious dwarfing phenomenon, with yellow and short leaves.Furthermore, chlorophyll content was lower than other genotypes. In addition, the SBPase activity of transgenic lines was 1.4 times of wild type, 1.9 times of the mutant.The RuBP yield and starch content were also higher than those of wild type and the mutant. The yield of RuBP in transgenic plants was 1.37 and 1.76 times of the wild type and the mutant, respectively.The starch content of the transgenic lines reached 50.26μg/g, while that of the mutants was not detected.

ConclusionThese results indicate that PdSBPase plays a vital role in the formation of RuBP and starch and other polysaccharides synthesis, and can promote plants to accumulate more carbohydrates and then positively regulate the photosynthetic capacity of plants.