Sharma Shagun, Negi Shivanti, Kumar Pankaj, Irfan Mohammad
Department of Biotechnology, Dr. Y.S, Parmar University of Horticulture and Forestry, Solan, Himachal Pradesh, India.
Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, USA.
Protoplasma. 2025 Apr 3. doi: 10.1007/s00709-025-02062-0.
High altitude conditions pose a significant challenge to all earth's inhabitants including flora. Low atmospheric pressure (thin air), intense ultraviolet (UV) light, and ultra-low temperatures combine to cause oxidative stress in plants. In these abiotic stress conditions, plants exhibit various ecophysiological, morphological, and biochemical adaptations to cope with stress. Morphologically, plants may develop smaller, thicker leaves with protective trichomes or waxy cuticles against intense UV radiation, and minimize water loss in the thin, dry air. However biochemically, plants increase the production of UV-absorbing compounds like flavonoids and phenolic acids along with antioxidant enzymes for neutralizing reactive oxygen species (ROS). To protect against these stress conditions plants start producing specialized metabolites, i.e., isoprenoids, phenolic acids, flavonoids, sterols, carotenoids, etc. The production of these specialized metabolites occurs through MEP (methylerythritol phosphate) and MVA (mevalonic acid) pathways. Although, this article aims to review the scientific complexities of high-altitude plants by providing an in-depth explanation of the MEP pathway, including its regulation, sources and causes of oxidative stress in plants, functions and roles of isoprenoids in stress tolerance, and the adaptation strategies that support alpine plant survival and acclimation. The MEP pathway's products, several carotenoids, viz., phytoene, lycopene, β-carotene, etc., and terpenoids, viz., geraniol, citral, phytol, etc., act as potent scavengers of ROS, providing defense against oxidative damage. Also, phytohormones, viz., abscisic acid, salicylic acid, and jasmonic acid play crucial roles in modulating plant responses to oxidative stress. To date, little scientific literature is available specifically on high-altitude plants with respect to MEP pathway and oxidative stress management. Understanding the interaction between the MEP pathway and oxidative stress in high-altitude plants can provide insight into the implications for improving crop resilience and producing bioactive chemicals with potential human health benefits.
高海拔环境对包括植物群在内的地球上所有生物都构成了重大挑战。低气压（空气稀薄）、强烈的紫外线（UV）和超低温共同作用，导致植物产生氧化应激。在这些非生物胁迫条件下，植物表现出各种生态生理、形态和生化适应机制来应对胁迫。在形态上，植物可能会长出更小、更厚的叶子，并带有保护性的毛状体或蜡质角质层，以抵御强烈的紫外线辐射，并在稀薄、干燥的空气中尽量减少水分流失。然而在生化方面，植物会增加类黄酮和酚酸等紫外线吸收化合物的产量，同时增加抗氧化酶的产生，以中和活性氧（ROS）。为了抵御这些胁迫条件，植物开始产生特殊的代谢产物，即类异戊二烯、酚酸、类黄酮、甾醇、类胡萝卜素等。这些特殊代谢产物的产生通过甲基赤藓糖醇磷酸（MEP）途径和甲羟戊酸（MVA）途径。尽管如此，本文旨在通过深入解释MEP途径，包括其调控、植物氧化应激的来源和原因、类异戊二烯在胁迫耐受性中的功能和作用，以及支持高山植物生存和适应的适应策略，来综述高海拔植物的科学复杂性。MEP途径的产物，几种类胡萝卜素，即八氢番茄红素、番茄红素、β-胡萝卜素等，以及萜类化合物，即香叶醇、柠檬醛、叶绿醇等，作为强大的ROS清除剂，提供抗氧化损伤的防御。此外，植物激素，即脱落酸、水杨酸和茉莉酸在调节植物对氧化应激的反应中起着关键作用。迄今为止，关于高海拔植物在MEP途径和氧化应激管理方面的科学文献很少。了解高海拔植物中MEP途径与氧化应激之间的相互作用，有助于深入了解提高作物抗逆性以及生产对人类健康有益的生物活性化学品的意义。
