Increased energy sequestration in Nicotiana tabacum overexpressing UGPase and SPP genes in mesophyll.

Abstract Transgenic Nicotiana tabacum with cDNA coding for uridine diphosphate glucose and sucrose phosphate phosphatase from Hordeum vulgare expressed from chrysanthemum rubisco small subunit promoter shows high expression of these transgenes in young leaves and low in roots. Although the activity of this promoter decreased during leaves development, even in fully developed leaves it was over 10 times higher than the expression of the native genes of these enzymes. The plants overexpressing the transgenes grew faster and started the generative phase earlier than the control plants, without any disturbances in leaves, flower and seed development. The dry weight of the transgenic plants at the end of the generative phase was slightly higher than in the control group and showed a greater proportion of carbohydrates. The content of lignin, cellulose and hemicellulose was higher in the transgenic plants than in the control plants, and similar differences showed the energy value of these plants. A comparison of the energy value sequestered in the aerial part of these plant showed that the transgenic plants stored up to 18% more energy than the control plants. Mesophyll-specific overexpression of the transgenes showed beneficial effects - faster plants growth and higher accumulation of energy in the transgenic plants than in the controls. This effect was achieved in N. tabacum, a plant without specific storage organs or tissues. The use of a promoter directing expression of transgenes into mesophyll cells allowed to increase the efficiency of the selected metabolic pathway - photosynthesis-dependent sucrose synthesis.