Role of the Polygalacturonidase Inhibitor Protein in the Ripening of Apples and Their Resistance to Monilia fructigena, a Causative Agent of Fruit Rot

Abstract

The rate of superoxide dismutase (SOD) accumulation in Rauwolfia serpentine Benth. cell culture under heat shock conditions (3 h, 45 degrees C) decreased insignificantly (by 4%), whereas low positive temperature (24 h, 7 degrees C) caused a drastic drop (by 48%). The observed decrease in the level of SOD activity resulted from a slowdown of the biosynthesis rate of the enzyme and decrease in its concentration in the cultivated cells. In addition, a compensatory decrease in degradation of the active protein (Kd) was observed at low positive temperatures and, consequently, an increase in its half-life (t1/2), compensating partially for a deficiency in de novo synthesized SOD molecules. The parameters studied restored after a 24-h adaptation of cells under standard temperature conditions.