Structural and Thermodynamic Characteristics of Potato Starches Depending on the Plant Genotype and Conditions of Their Cultivation

The creation of new highly productive forms of potato by genetic engineering methods raises the question about the quality of transgenic tubers, which first of all relates to the properties of important storage compound such as starch. The article presents the results of studies aiming to the analysis of morphology, structure, and thermodynamic parameters of starch extracted from the potato tubers expressing the tms1 auxin biosynthesis gene from Agrobacterium tumefaciens and characterized by increased productivity in vitro. The transformed and control plants were cultivated in vitro on artificial sterile medium, as well as in vivo in the soil. The methods of scanning electron microscopy, wide-angle X-ray scattering, and differential scanning microcalorimetry were used in the work. It was established that the transformation of plants with the construction with the tms1 gene under the control of the patatin gene promoter causes significant changes in a number of thermodynamic parameters of starch, first of all an increase in the thickness of crystalline lamella and melting temperature, which apparently reflects the increase in the structural ordering of the main starch fraction (approximately 90%) in the tubers of these transformants. Along with this, the effect of accumulating fractions with a less ordered structure in the starch composition, correlating with the ectopic expression of the tms1 auxin biosynthesis gene, was established. At the same time, the B type of the polymorphic structure of starch remains unchanged. However, the detected changes mainly affected starch of the plants, cultivated in vitro. The starch of transgenic plants cultivated in the soil differs little in its basic characteristics from the starch of nontransgenic control plants.