Lázaro-González Alba, Gargallo-Garriga Albert, Hódar José Antonio, Sardans Jordi, Oravec Michal, Urban Otmar, Peñuelas Josep, Zamora Regino
Department of Ecology, Terrestrial Ecology Research Group, University of Granada, Granada, Spain.
CSIC, Global Ecology Unit CREAF-CSIC-UAB, Bellaterra, Spain.
Plant Cell Environ. 2021 Nov;44(11):3655-3666. doi: 10.1111/pce.14179. Epub 2021 Sep 16.
Mistletoe-host systems exemplify an intimate and chronic relationship where mistletoes represent protracted stress for hosts, causing long-lasting impact. Although host changes in morphological and reproductive traits due to parasitism are well known, shifts in their physiological system, altering metabolite concentrations, are less known due to the difficulty of quantification. Here, we use ecometabolomic techniques in the plant-plant interaction, comparing the complete metabolome of the leaves from mistletoe (Viscum album) and needles from their host (Pinus nigra), both parasitized and unparasitized, to elucidate host responses to plant parasitism. Our results show that mistletoe acquires metabolites basically from the primary metabolism of its host and synthesizes its own defence compounds. In response to mistletoe parasitism, pines modify a quarter of their metabolome over the year, making the pine canopy metabolome more homogeneous by reducing the seasonal shifts in top-down stratification. Overall, host pines increase antioxidant metabolites, suggesting oxidative stress, and also increase part of the metabolites required by mistletoe, which act as a permanent sink of host resources. In conclusion, by exerting biotic stress and thereby causing permanent systemic change, mistletoe parasitism generates a new host-plant metabolic identity available in forest canopy, which could have notable ecological consequences in the forest ecosystem.
槲寄生-宿主系统体现了一种密切且长期的关系，其中槲寄生对宿主而言意味着长期的压力，会造成持久的影响。尽管寄生导致宿主在形态和繁殖特征上的变化已为人熟知，但由于难以量化，其生理系统中代谢物浓度的变化却鲜为人知。在此，我们在植物-植物相互作用中运用生态代谢组学技术，比较了寄生和未寄生的槲寄生（欧洲槲寄生）叶片及宿主（黑松）针叶的完整代谢组，以阐明宿主对植物寄生的反应。我们的结果表明，槲寄生主要从其宿主的初级代谢中获取代谢物，并合成自身的防御化合物。作为对槲寄生寄生的反应，黑松在一年中会改变其四分之一的代谢组，通过减少自上而下分层中的季节性变化，使松树冠层的代谢组更加均匀。总体而言，宿主黑松会增加抗氧化代谢物，这表明存在氧化应激，同时还会增加槲寄生所需的部分代谢物，而这些代谢物成为了宿主资源的永久消耗地。总之，通过施加生物胁迫并由此导致永久性的系统变化，槲寄生寄生在森林冠层中产生了一种新的宿主-植物代谢特征，这可能会对森林生态系统产生显著的生态影响。
