Enhanced expression of serine protease inhibitor StSPI128 alleviates the enzymatic browning in fresh-cut potatoes via increasing antioxidant abilities

Enzymatic browning is problematic for the fresh-processed potato (Solanum tuberosum L.) industry. Previously, we identified a serine protease inhibitor gene StSPI128, which may alleviate potato browning. Therefore, the effects of StSPI128 on potato browning and browning-related factors were investigated by overexpressing the gene in this study. The results showed that overexpression of StSPI128 significantly alleviated potato browning and increased phenolic content. However, not all the decreases in protease activities or accumulations of total free amino acid and tyrosine caused by StSPI128-overexpression were significant among three transgenic lines. Besides, overexpression of StSPI128 reduced PPO activity in potatoes. Moreover, overexpression of StSPI128 increased the total antioxidant abilities and membrane stability, elevated SOD and CAT activities, and decreased ROS and MDA accumulation. In vitro experiments demonstrated that the variation in browning-substrates and PPO activities did not induce the differences in potato browning. These results indicated that enhanced expression of StSPI128 alleviated potato browning mainly by increasing antioxidant ability, not via altering browning substrates or PPO activities. This work suggested that StSPI128 is a promising potential target for browning control in fresh-processed potatoes.