Postharvest nicotinamide treatment modifies the redox status in highbush blueberry (Vaccinum corymbosum L.) fruit during storage

Abstract

Increased expression and activity of PARP family enzymes is associated with perturbations in the energy metabolism and redox status of the fruit after harvest. Because nicotinamide is a competitive inhibitor of PARP enzymes, in the present study we set out to check whether nicotinamide treatment of highbush blueberry fruit would affect PARP-1 expression, energy metabolism, and redox status in the fruit, and whether nicotinamide would protect the tissue from the pro-oxidative effects of UV-C radiation. For this purpose, the fruits of Vaccinum corymbosum L. cv. Duke, were treated with a 10 mM aqueous solution of nicotinamide and additionally co-treated with UV-C radiation, which were then stored for 7 d at 10 °C. We observed in the course of the study that nicotinamide clearly contributes to the reduction of oxidative stress in blueberry fruit. This was observed in the form of reduced PARP-1 expression in both UV-C irradiated and non-UV-C irradiated fruit. Reduced PARP-1 expression, in turn, inhibited NAD⁺ loss, which contributed to higher ATP availability and consequently less ROS accumulation in the tissue. Furthermore, nicotinamide treatment reduced the decline of low-molecular weight of antioxidants content in UV-C-irradiated fruit.