Department of Agriculture, Food, Environment and Forestry (DAGRI), University of Florence, 50019 Sesto Fiorentino, Florence, Italy.
Institute for Sustainable Plant Protection (IPSP), National Research Council of Italy, 50019 Sesto Fiorentino, Florence, Italy.
Int J Mol Sci. 2022 May 9;23(9):5284. doi: 10.3390/ijms23095284.
Plants evolved an impressive arsenal of multifunctional specialized metabolites to cope with the novel environmental pressures imposed by the terrestrial habitat when moving from water. Here we examine the multifarious roles of flavonoids in plant terrestrialization. We reason on the environmental drivers, other than the increase in UV-B radiation, that were mostly responsible for the rise of flavonoid metabolism and how flavonoids helped plants in land conquest. We are reasonably based on a nutrient-deficiency hypothesis for the replacement of mycosporine-like amino acids, typical of streptophytic algae, with the flavonoid metabolism during the water-to-land transition. We suggest that flavonoids modulated auxin transport and signaling and promoted the symbiosis between plants and fungi (e.g., arbuscular mycorrhizal, AM), a central event for the conquest of land by plants. AM improved the ability of early plants to take up nutrients and water from highly impoverished soils. We offer evidence that flavonoids equipped early land plants with highly versatile "defense compounds", essential for the new set of abiotic and biotic stressors imposed by the terrestrial environment. We conclude that flavonoids have been multifunctional since the appearance of plants on land, not only acting as UV filters but especially improving both nutrient acquisition and biotic stress defense.
植物进化出了令人印象深刻的多功能特化代谢物武器库，以应对从水中转移到陆地时所面临的新型环境压力。在这里，我们研究了类黄酮在植物陆地化过程中的多种作用。我们推测，除了 UV-B 辐射增加之外，还有其他环境驱动因素导致类黄酮代谢的兴起，以及类黄酮如何帮助植物征服陆地。我们基于一种营养缺乏假说，认为在水到陆的过渡过程中，典型的绿藻的菌多酚类氨基酸被类黄酮代谢所取代。我们提出，类黄酮调节了生长素的运输和信号转导，并促进了植物与真菌（如丛枝菌根，AM）之间的共生关系，这是植物征服陆地的中心事件。AM 提高了早期植物从高度贫瘠土壤中吸收养分和水分的能力。我们提供的证据表明，类黄酮为早期陆地植物提供了多功能的“防御化合物”，这对于陆地环境所施加的新的非生物和生物胁迫因素至关重要。我们的结论是，类黄酮自植物出现在陆地上以来就具有多功能性，不仅可以作为紫外线过滤器，而且特别可以改善营养物质的获取和生物胁迫防御。
