Tian Jie, Cheng Yaqi, Kong Xiangyu, Liu Min, Jiang Fangling, Wu Zhen
College of Horticulture, Ministry of Agriculture, Nanjing Agricultural University/Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, Nanjing, 210095, People's Republic of China.
Protoplasma. 2017 Jan;254(1):379-388. doi: 10.1007/s00709-016-0957-z. Epub 2016 Mar 5.
Hyperhydricity is a physiological disorder associated with oxidative stress. Reactive oxygen species (ROS) generation in plants is initiated by various enzymatic sources, including plasma membrane-localized nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, cell wall-bound peroxidase (POD), and apoplastic polyamine oxidase (PAO). The origin of the oxidative burst associated with hyperhydricity remains unknown. To investigate the role of NADPH oxidases, POD, and PAO in ROS production and hyperhydricity, exogenous hydrogen peroxide (HO) and inhibitors of each ROS-producing enzyme were applied to explore the mechanism of oxidative stress induction in garlic plantlets in vitro. A concentration of 1.5 mM HO increased endogenous ROS production and hyperhydricity occurrence and enhanced the activities of NADPH oxidases, POD, and PAO. During the entire treatment period, NADPH oxidase activity increased continuously, whereas POD and PAO activities exhibited a transient increase and subsequently declined. Histochemical and cytochemical visualization demonstrated that specific inhibitors of each enzyme effectively suppressed ROS accumulation. Moreover, superoxide anion generation, HO content, and hyperhydric shoot frequency in HO-stressed plantlets decreased significantly. The NADPH oxidase inhibitor was the most effective at suppressing superoxide anion production. The results suggested that NADPH oxidases, POD, and PAO were responsible for endogenous ROS induction. NADPH oxidase activation might play a pivotal role in the oxidative burst in garlic plantlets in vitro during hyperhydricity.
玻璃化是一种与氧化应激相关的生理紊乱。植物中活性氧（ROS）的产生由多种酶源引发，包括质膜定位的烟酰胺腺嘌呤二核苷酸磷酸（NADPH）氧化酶、细胞壁结合的过氧化物酶（POD）和质外体多胺氧化酶（PAO）。与玻璃化相关的氧化爆发的起源尚不清楚。为了研究NADPH氧化酶、POD和PAO在ROS产生及玻璃化中的作用，将外源过氧化氢（H₂O₂）和每种ROS产生酶的抑制剂应用于体外培养的大蒜幼苗，以探究氧化应激诱导的机制。1.5 mM的H₂O₂浓度增加了内源性ROS的产生和玻璃化的发生，并增强了NADPH氧化酶、POD和PAO的活性。在整个处理期间，NADPH氧化酶活性持续增加，而POD和PAO活性则先短暂增加，随后下降。组织化学和细胞化学观察表明，每种酶的特异性抑制剂有效抑制了ROS的积累。此外，H₂O₂胁迫幼苗中的超氧阴离子产生、H₂O₂含量和玻璃化苗频率显著降低。NADPH氧化酶抑制剂在抑制超氧阴离子产生方面最有效。结果表明，NADPH氧化酶、POD和PAO是内源性ROS诱导的原因。在体外培养的大蒜幼苗玻璃化期间，NADPH氧化酶的激活可能在氧化爆发中起关键作用。
