College of Life Science and Biotechnology, Ecological Security and Protection Key laboratory of Sichuan Province, Mianyang Normal University, Mianxing Road West 166, Mianyang, 621000, PR China.
Chair of Tree Physiology, Institute of Forest Sciences, University of Freiburg, Georges-Köhler-Allee 53, Freiburg, D-79110, Germany.
Biol Rev Camb Philos Soc. 2024 Aug;99(4):1524-1536. doi: 10.1111/brv.13079. Epub 2024 Apr 1.
In their environment, plants are exposed to a multitude of abiotic and biotic stresses that differ in intensity, duration and severity. As sessile organisms, they cannot escape these stresses, but instead have developed strategies to overcome them or to compensate for the consequences of stress exposure. Defence can take place at different levels and the mechanisms involved are thought to differ in efficiency across these levels. To minimise metabolic constraints and to reduce the costs of stress defence, plants prioritise first-line defence strategies in the apoplastic space, involving ascorbate, defensins and small peptides, as well as secondary metabolites, before cellular processes are affected. In addition, a large number of different symplastic mechanisms also provide efficient stress defence, including chemical antioxidants, antioxidative enzymes, secondary metabolites, defensins and other peptides as well as proteins. At both the symplastic and the apoplastic level of stress defence and compensation, a number of specialised transporters are thought to be involved in exchange across membranes that still have not been identified, and information on the regeneration of different defence compounds remains ambiguous. In addition, strategies to overcome and compensate for stress exposure operate not only at the cellular, but also at the organ and whole-plant levels, including stomatal regulation, and hypersensitive and systemic responses to prevent or reduce the spread of stress impacts within the plant. Defence can also take place at the ecosystem level by root exudation of signalling molecules and the emission of volatile organic compounds, either directly or indirectly into the rhizosphere and/or the aboveground atmosphere. The mechanisms by which plants control the production of these compounds and that mediate perception of stressful conditions are still not fully understood. Here we summarise plant defence strategies from the cellular to ecosystem level, discuss their advantages and disadvantages for plant growth and development, elucidate the current state of research on the transport and regeneration capacity of defence metabolites, and outline insufficiently explored questions for further investigation.
在它们所处的环境中，植物会受到多种非生物和生物胁迫的影响，这些胁迫在强度、持续时间和严重程度上都有所不同。作为固着生物，它们无法逃避这些胁迫，而是发展出了应对或补偿胁迫暴露后果的策略。防御可以在不同层面进行，而涉及的机制在这些层面上的效率被认为是不同的。为了最小化代谢限制并降低应激防御的成本，植物在质外体空间中优先采用第一线防御策略，包括抗坏血酸、防御素和小肽以及次生代谢物，然后再影响细胞过程。此外，大量不同的共生机制也提供了有效的应激防御，包括化学抗氧化剂、抗氧化酶、次生代谢物、防御素和其他肽以及蛋白质。在应激防御和补偿的质外体和共生体层面上，许多专门的转运蛋白被认为参与了尚未确定的跨膜交换，并且关于不同防御化合物再生的信息仍然模棱两可。此外，克服和补偿应激暴露的策略不仅在细胞层面上运作，而且在器官和整株植物层面上运作，包括气孔调节以及对敏感和系统响应，以防止或减少应激影响在植物体内的传播。防御也可以在生态系统层面上通过信号分子的根分泌和挥发性有机化合物的排放来进行，无论是直接还是间接进入根际和/或地上大气。植物控制这些化合物产生的机制以及介导对胁迫条件的感知的机制仍不完全清楚。在这里，我们从细胞到生态系统层面总结了植物防御策略，讨论了它们对植物生长和发育的优缺点，阐明了防御代谢物运输和再生能力的研究现状，并概述了进一步研究中尚未探索的问题。
