Poisonous Plant Research Laboratory, Agricultural Research Service, United States Department of Agriculture, 1150 E. 1400 N., Logan, UT, 84341, USA.
J Chem Ecol. 2009 Oct;35(10):1272-8. doi: 10.1007/s10886-009-9710-9. Epub 2009 Nov 11.
Locoweeds are Astragalus and Oxytropis species that contain the toxic alkaloid swainsonine. Swainsonine accumulates in all parts of the plant with the highest concentrations found in the above ground parts. A fungal endophyte, Undifilum oxytropis, found in locoweed plant species, is responsible for the synthesis of swainsonine. By using quantitative PCR, the endophyte can be quantified in locoweed species. Endophyte amounts differ between plant parts and in some instances do not mirror the concentrations of swainsonine in the corresponding parts. Two groups of Oxytropis sericea were identified: one that accumulated high concentrations of swainsonine and another where swainsonine was not detected, or concentrations were near the detection threshold. The plants with high swainsonine concentrations had quantitatively higher amounts of endophyte. Alternatively, plants with low or no swainsonine detected had quantitatively lower endophyte amounts. In addition, swainsonine and endophyte concentrations were not distributed uniformly within the same plant when separated into stalks (leaves, scape(s), and flowers/pods). These findings provide evidence as to why plants in the same population accumulate different concentrations of swainsonine, and they have important implications for sampling of locoweed plants.
疯草是黄芪和棘豆属的物种，含有毒性生物碱苦马豆素。苦马豆素在植物的所有部位积累，地上部分的浓度最高。一种真菌内生菌，即棘豆内生真菌，是苦马豆素合成的原因。通过使用定量 PCR，可以在疯草物种中定量内生菌。内生菌的数量因植物部位而异，在某些情况下，内生菌的数量与相应部位的苦马豆素浓度并不对应。鉴定出了两种棘豆属 Sericea：一种积累了高浓度的苦马豆素，另一种则未检测到苦马豆素，或浓度接近检测阈值。苦马豆素浓度高的植物内生菌数量较高。相反，苦马豆素浓度低或未检测到的植物内生菌数量较低。此外，当将同一植物分为茎（叶、茎和花/荚）时，苦马豆素和内生菌的浓度在同一植物内分布不均匀。这些发现为为什么同一种群中的植物积累不同浓度的苦马豆素提供了证据，并且对疯草植物的采样具有重要意义。
