Department of Biology, Colorado State University, Fort Collins, Colorado 80523, USA.
Plant Physiol. 2012 Aug;159(4):1834-44. doi: 10.1104/pp.112.199307. Epub 2012 May 29.
The goal of this study was to investigate how plant selenium (Se) hyperaccumulation may affect ecological interactions and whether associated partners may affect Se hyperaccumulation. The Se hyperaccumulator Astragalus bisulcatus was collected in its natural seleniferous habitat, and x-ray fluorescence mapping and x-ray absorption near-edge structure spectroscopy were used to characterize Se distribution and speciation in all organs as well as in encountered microbial symbionts and herbivores. Se was present at high levels (704-4,661 mg kg(-1) dry weight) in all organs, mainly as organic C-Se-C compounds (i.e. Se bonded to two carbon atoms, e.g. methylselenocysteine). In nodule, root, and stem, up to 34% of Se was found as elemental Se, which was potentially due to microbial activity. In addition to a nitrogen-fixing symbiont, the plants harbored an endophytic fungus that produced elemental Se. Furthermore, two Se-resistant herbivorous moths were discovered on A. bisulcatus, one of which was parasitized by a wasp. Adult moths, larvae, and wasps all accumulated predominantly C-Se-C compounds. In conclusion, hyperaccumulators live in association with a variety of Se-resistant ecological partners. Among these partners, microbial endosymbionts may affect Se speciation in hyperaccumulators. Hyperaccumulators have been shown earlier to negatively affect Se-sensitive ecological partners while apparently offering a niche for Se-resistant partners. Through their positive and negative effects on different ecological partners, hyperaccumulators may influence species composition and Se cycling in seleniferous ecosystems.
本研究旨在探讨植物硒（Se）超积累如何影响生态相互作用，以及相关共生体是否会影响硒的超积累。本研究在天然富硒生境中采集了硒超积累植物紫云英（Astragalus bisulcatus），并利用 X 射线荧光映射和 X 射线吸收近边结构光谱技术，对所有器官以及遇到的微生物共生体和食草动物中的硒分布和形态进行了表征。所有器官中的硒含量都很高（704-4661mg/kg 干重），主要以有机 C-Se-C 化合物（即与两个碳原子结合的硒，如甲基硒代半胱氨酸）的形式存在。在根瘤、根和茎中，高达 34%的硒以元素硒的形式存在，这可能是由于微生物的活性。除了固氮共生体，植物还含有一种内生真菌，会产生元素硒。此外，在紫云英上发现了两种具有耐硒性的食草性飞蛾，其中一种被黄蜂寄生。成虫、幼虫和黄蜂都主要积累 C-Se-C 化合物。总之，超积累植物与多种具有耐硒性的生态伙伴共生。在这些共生体中，微生物内共生体可能会影响超积累植物中的硒形态。此前已经表明，超积累植物会对硒敏感的生态伙伴产生负面影响，而显然会为耐硒伙伴提供一个小生境。通过对不同生态伙伴的积极和消极影响，超积累植物可能会影响富硒生态系统中的物种组成和硒循环。
