Enzymatic browning is one of the main problems during storage of fresh-cut apples. Pre-cut treatment with L-cysteine has been shown to effectively inhibit browning on fresh-cut apples, but its mechanism is still unclear. This work investigated the browning-related differentially expressed genes (DEGs) after pre-cut treatment with L-cysteine, and analyzed the relationship between ethylene biosynthesis and L-cysteine through combining with aminoethoxyvinylglycine (AVG) treatment. The results indicated that lots of DEGs related to ethylene biosynthesis on fresh-cut apples were up-regulated, and the ethylene content, 1-aminocyclopropane-1-carboxilic acid (ACC) synthase and ACC oxidase activities were also improved after pre-cut L-cysteine. Further analysis found that AVG alleviated the effects of L-cysteine on the browning index, polyphenol oxidase (PPO) activity, peroxidase (POD) activity, catalase (CAT) activity and glutathione reductase (GR) activity of fresh-cut apples. Also, L-cysteine combined with AVG pretreatment reduced total phenol content and improved phenylalanine ammonia-lyase (PAL) activity compared with individual L-cysteine pretreatment. In addition, ethylene pretreatment also inhibited the browning and PPO activity, and increased POD activity, CAT activity and total phenol content on fresh-cut apples, which was better than that of L-cysteine combined with AVG pretreatment. This indirectly confirmed that pre-cut L-cysteine inhibited the browning of fresh-cut apples partly through regulating ethylene biosynthesis in vivo. The work proposes a novelty viewpoint that enhanced ethylene accumulation before cutting is helpful to inhibit the browning of fresh-cut apples.

中文翻译：

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转录组和物理化学分析揭示了乙烯对鲜切苹果的预切 L-半胱氨酸的潜在抗褐变机制


酶促褐变是鲜切苹果储存过程中的主要问题之一。用 L-半胱氨酸进行预切处理已被证明可以有效抑制鲜切苹果的褐变，但其机制尚不清楚。本研究研究了 L-半胱氨酸预切割处理后褐变相关的差异表达基因 （DEGs），并结合氨基乙氧基乙烯基甘氨酸 （AVG） 处理分析了乙烯生物合成与 L-半胱氨酸的关系。结果表明，鲜切苹果中大量与乙烯生物合成相关的 DEGs 上调，预切 L-半胱氨酸后乙烯含量、1-氨基环丙烷-1-羧酸 （ACC） 合酶和 ACC 氧化酶活性也有所提高。进一步分析发现，AVG 减轻了 L-半胱氨酸对鲜切苹果褐变指数、多酚氧化酶 （PPO） 活性、过氧化物酶 （POD） 活性、过氧化氢酶 （CAT） 活性和谷胱甘肽还原酶 （GR） 活性的影响。此外，与单个 L-半胱氨酸预处理相比，L-半胱氨酸联合 AVG 预处理降低了总酚含量并提高了苯丙氨酸解氨酶 （PAL） 活性。此外，乙烯预处理还抑制了鲜切苹果的褐变和 PPO 活性，提高了 POD 活性、CAT 活性和总酚含量，优于 L-半胱氨酸联合 AVG 预处理。这间接证实了预切 L-半胱氨酸部分通过调节体内乙烯生物合成来抑制鲜切苹果的褐变。这项工作提出了一个新颖的观点，即在切割前增强乙烯积累有助于抑制鲜切苹果的褐变。