The Opposite Effect of Low Temperature on the Pho1a Starch Phosphorylase Gene Expression in Solanum tuberosum L. Tubers and Petota Species Leaves

Starch turnover is important for plant response to abiotic stresses and plastidic starch phosphorylase Pho1a is a key enzyme regulating starch metabolism. In this study, we identified Pho1a coding sequences in seven wild tuber-bearing potato species. In Solanum tuberosum cv. Nadezhda grown at normal conditions, Pho1a transcription was low; it was detected in stems, leaves, flowers, and roots. After harvest, Pho1a expression in tubers of 16 S. tuberosum cultivars was either absent or low but progressively increased during storage at +4 degrees C, which corresponded to an increase in the content of reducing sugars. In the leaves of both cultivated and wild potato species, exposure to short-term cold stress downregulated Pho1a expression, especially at night, and stimulated starch degradation, but there was no uniform diurnal pattern in Pho1a expression dynamics. These findings indicate that Pho1a may have different functions in storage and photosynthetic organs of potato.