Morphological and biochemical characteristics of potato plants expressing the invertase gene SUC2 from Saccharomyces cerevisiae, under cultivation in vitro

According to the main heterotrophy of the plants grown in vitro, disaccharide of sucrose as a carbohydrate source is used the most often. However, in the plant cells sucrose can’t be utilized for metabolism. Before using it must be split into gexoses by, for example, the key enzyme of carbohydrate metabolism-invertase. Assuming the direct contact of the root system with the nutrition medium, the apoplast invertase catalyzing hydrolysis of sucrose in the unoccupied cellular space (apoplast) is of a special interest. In this study, we assessed the influence of the constitutive expression of target-oriented gene of suc2, encoding extracellular invertase of the Saccharomyces cerevisiae yeasts (apoplastic version of enzyme localization) on morphological, physiological and biochemical traits of transformed potato grown in vitro in nonhormone nutritive medium of Murashige-Skooge (MS-medium). The comparison of various sugars (glucose, fructose and sucrose) showed that 2% sucrose in the medium is the best carbohydrate source for potato growth. We found out that during growth and development of the plants in MS-medium containing 2% sucrose the osmotic potential decreased, which indicated active assimilation of mineral and organic compounds. Meanwhile, the transformants compared to the control (non-transformed) plants utilized osmoticly active compounds (mainly, sucrose) more intensively. Sugar chromatographic assay in the leaves of both plants revealed dominant content of sucrose and glucose whereas fructose content was minor. The increased activity of the apoplastic invertase in transformants compared to that in the control plants promoted more active accumulation of metabolically active sugars: fructose in the apoplast, glucose and sucrose in the leaves; and especially, glucose in the roots. The inhibition of the growth by an increased glucose concentration in the transformants tissues was recorded. Morphological and metric analysis showed that the transformants had some decreased growth parameters (shoot length, the number of internodes, fresh biomass of the roots and leaves) and more watered tissues compared to those of the control plants. Morphological and biochemical difference between the plant lines is under discussion from the point of physiological role of the sugars and apoplastic invertase in plant life. Acknowledgments: The authors express their gratitude to the staff of M.Kh. Chailakhyan Laboratory of signal systems of ontogeny control IPP RAS and the group of Dr. Willmitzer (Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany) for providing potato plants for research. The article contains 5 Fig., 3 Tables, 32 Ref.

Keywords

Authors

References