Abstract Enzymatic browning greatly affects the quality of fresh-cut potatoes (Solanum tuberosum L.). The transcript level of a novel aspartic protease inhibitor gene, StASPI, was found significantly higher in browning-less potatoes than in browning-susceptible potatoes, and exogenous aspartic protease inhibitor Pepstatin A inhibited the browning of potato pulp. Therefore, we speculated that StASPI plays important roles in browning-resistance of potatoes. The effects of overexpressed-StASPI on browning, total free amino acids (FAAs), antioxidant enzyme activity and ROS accumulation in potatoes were investigated in this study. Results showed that overexpression of StASPI effectively reduced enzymatic browning after cutting, significantly decreased protease activity, and reduced the accumulation of total FAAs in potatoes. Browning degrees of transgenic potato mash were increased by supplementing exogenous FAAs, but the degrees were still significantly lower than that of wild-type (WT) mash. Furthermore, overexpression of StASPI decreased PPO activity, enhanced the activities of antioxidant enzymes SOD and CAT, and reduced H2O2 and O2˙― contents. These results indicated that overexpression of StASPI inhibited the enzymatic browning of potatoes, decreasing FAAs accumulation, reducing PPO activity, and enhancing activity of antioxidant enzymes. This study provides a new perspective on the strategies for inhibiting enzymatic browning of potatoes.

中文翻译：

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一种新型天冬氨酸蛋白酶抑制剂抑制马铃薯酶促褐变

摘要 酶促褐变严重影响鲜切马铃薯（Solanum tuberosum L.）的品质。发现新天冬氨酸蛋白酶抑制剂基因 StASPI 的转录水平在无褐变马铃薯中显着高于易褐变马铃薯，外源天冬氨酸蛋白酶抑制剂胃蛋白酶抑制剂 A 抑制马铃薯果肉褐变。因此，我们推测StASPI在马铃薯抗褐变中起重要作用。本研究调查了过表达 StASPI 对马铃薯褐变、总游离氨基酸 (FAA)、抗氧化酶活性和 ROS 积累的影响。结果表明，过表达StASPI有效减少了切后酶促褐变，显着降低了蛋白酶活性，减少了马铃薯中总FAA的积累。添加外源FAAs后转基因马铃薯醪的褐变程度有所提高，但仍显着低于野生型（WT）醪的褐变程度。此外，StASPI 的过表达降低了PPO 活性，增强了抗氧化酶SOD 和CAT 的活性，并降低了H2O2 和O2·― 的含量。这些结果表明，StASPI 的过表达抑制了马铃薯的酶促褐变，减少了 FAA 的积累，降低了 PPO 活性，并增强了抗氧化酶的活性。该研究为抑制马铃薯酶促褐变的策略提供了新的视角。增强抗氧化酶SOD和CAT的活性，降低H2O2和O2˙―含量。这些结果表明，StASPI 的过表达抑制了马铃薯的酶促褐变，减少了 FAA 的积累，降低了 PPO 活性，并增强了抗氧化酶的活性。该研究为抑制马铃薯酶促褐变的策略提供了新的视角。增强抗氧化酶SOD和CAT的活性，降低H2O2和O2˙―含量。这些结果表明，StASPI 的过表达抑制了马铃薯的酶促褐变，减少了 FAA 的积累，降低了 PPO 活性，并增强了抗氧化酶的活性。该研究为抑制马铃薯酶促褐变的策略提供了新的视角。