Pericarp browning is a major symptom of the quality deterioration in postharvest longan fruit. Previous studies show that the change in the quality of fresh produce is related to the level of energy status. The proton transport regulator such as dicyclohexylcarbodiimide (DCC) and disodium succinate (DS) can regulate the protons flux to affect the production of adenosine triphosphate (ATP) and the level of energy status. However, the mechanisms of proton transport regulator induced-the changes in the level of ATP and energy status in postharvest longan fruit in relation to longan pericarp browning remain unclear. In this work, the influences of DCC and DS-mediated the alteration of energy status on longan pericarp browning, energy metabolism, and respiratory metabolism were investigated. Results showed that DCC treatment accelerated pericarp browning development and elevated respiration rate as compared to the control. Longans treated with DCC exhibited higher levels of ATP, adenosine diphosphate (ADP), and energy charge, as well as higher activities of H-ATPase, Ca-ATPase, and Mg-ATPase in the mitochondrial, vacuole, and plasma membranes. Additionally, DCC treatment increased the activities of phosphoglucose isomerase (PGI), succinate dehydrogenase (SDH), cytochrome C oxidase (CCO), ascorbic acid oxidase (AAO), and alternative oxidase (AOX), along with higher contents of ubiquinol (QH), nicotinamide adenine dinucleotide (NAD), and the reduced form of NAD (NADH). Whereas, DCC treatment decreased the activities of nicotinamide adenine dinucleotide kinase (NADK), and glucose-6-phosphate dehydrogenase (G-6-PDH) + 6-phosphaogluconate dehydrogenase (6-PGDH), and lowered the contents of ubiquinone (Q), nicotinamide adenine dinucleotide phosphate (NADP), and the reduced form of NADP (NADPH). These results revealed that DCC treatment accelerated energy deficit, disrupted energy balance, and promoted respiratory metabolism through enhancing embden-meyerhof-parnas (EMP), tricarboxylic acid (TCA) cycle, and cytochrome pathway (CCP) while attenuating pentose phosphate pathway (PPP), ultimately leading to the aggravated longan pericarp browning. Conversely, DS treatment delayed longan pericarp browning by acting on the opposite effects of DCC treatment.

中文翻译：

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能量和呼吸代谢参与二环己基碳二亚胺和琥珀酸二钠介导的能量状态改变调节新鲜龙眼果皮褐变

果皮褐变是龙眼果实采后品质恶化的主要症状。此前的研究表明，生鲜农产品品质的变化与能量状态的水平有关。质子传输调节剂如二环己基碳二亚胺（DCC）和琥珀酸二钠（DS）可以调节质子通量，从而影响三磷酸腺苷（ATP）的产生和能量状态的水平。然而，质子转运调节剂引起龙眼果实采后ATP水平和能量状态变化与龙眼果皮褐变相关的机制尚不清楚。本工作研究了DCC和DS介导的能量状态改变对龙眼果皮褐变、能量代谢和呼吸代谢的影响。结果表明，与对照相比，DCC 处理加速了果皮褐变发育并提高了呼吸速率。经过 DCC 处理的龙眼在线粒体、液泡和质膜中表现出更高水平的 ATP、二磷酸腺苷 (ADP) 和能量电荷，以及更高的 H-ATP 酶、Ca-ATP 酶和 Mg-ATP 酶活性。此外，DCC 处理增加了磷酸葡萄糖异构酶 (PGI)、琥珀酸脱氢酶 (SDH)、细胞色素 C 氧化酶 (CCO)、抗坏血酸氧化酶 (AAO) 和替代氧化酶 (AOX) 的活性，以及​​更高的泛醇 (QH) 含量、烟酰胺腺嘌呤二核苷酸 (NAD) 和 NAD 的还原形式 (NADH)。而DCC处理降低了烟酰胺腺嘌呤二核苷酸激酶（NADK）和葡萄糖-6-磷酸脱氢酶（G-6-PDH）+6-磷酸葡萄糖酸脱氢酶（6-PGDH）的活性，并降低了泛醌（Q）的含量、烟酰胺腺嘌呤二核苷酸磷酸 (NADP) 和 NADP (NADPH) 的还原形式。这些结果表明，DCC 治疗通过增强 embden-meyerhof-parnas (EMP)、三羧酸 (TCA) 循环和细胞色素途径 (CCP) 同时减弱磷酸戊糖途径 (PPP) 加速能量不足、破坏能量平衡并促进呼吸代谢，最终导致龙眼果皮褐变加剧。相反，DS 处理通过与 DCC 处理相反的作用来延迟龙眼果皮褐变。