Effect of insertion of apoplastic invertase gene on photosynthesis of potato plants grown at various light intensities

We studied the influence of yeast invertase gene (inv), with the apoplastic localization of the enzyme, on photosynthesis of potato plants (Solanum tuberosum L., cv. Desiree) grown at various irradiances. Plants were raised in vitro, planted in soil in gauze-insulated stands, and grown at irradiances of 100, 200, and 380 W/m² of photosynthetically active radiation. Wild-type plants (WT) and the plants transformed with yeast invertase gene (B33-inv) were used. In the beginning of flowering stage, assimilation of ¹⁴CO₂ and ¹⁴C incorporation into photosynthates were measured. Irrespective of irradiance, the carbon assimilation was higher in WT plants, than in transformed B33-inv plants. In the plants studied, we observed divergent light dependences of ¹⁴C inclusion into sucrose: the highest labeling was observed at low irradiance in WT plants and at high irradiance in B33-inv transformed plants. The content of ¹⁴C incorporated into amino acids changed in the opposite direction compared to ¹⁴C incorporation into sucrose. Irrespective of the plant type, similar light dependences were observed for ¹⁴C content in the products of glycolate metabolism and in glycerate. At the intermediate irradiance, the patterns of ¹⁴C distribution among photosynthetic products showed minimal differences between the plants of two types. The role of apoplast invertase in sugar export from the leaf and the possible control of plant productivity through this enzyme activity are discussed.