DeTar Rachael Ann, Alford Élan R, Pilon-Smits Elizabeth A H
Biology Department, Colorado State University, Fort Collins, CO 80523, USA.
Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA; Department of Forest and Rangeland Stewardship, Colorado State University, Fort Collins, CO 80523, USA.
J Plant Physiol. 2015 Jul 1;183:32-40. doi: 10.1016/j.jplph.2015.05.009. Epub 2015 Jun 3.
Some species hyperaccumulate selenium (Se) upwards of 0.1% of dry weight. This study addressed whether Se hyperaccumulators also accumulate and tolerate more molybdenum (Mo). A field survey revealed on average 2-fold higher Mo levels in three hyperaccumulator Astragali compared to three nonaccumulator Astragali, which were not significantly different. Next, a controlled study was performed where hyperaccumulators Astragalus racemosus and Astragalus bisulcatus were compared with nonaccumulators Astragalus drummondii and Astragalus convallarius for Mo accumulation and tolerance, alone or in the presence of Se. When grown on agar media with 0, 12, 24 or 48 mg L(-1) molybdate and/or 0, 1.6 or 3.2 mg L(-1) selenate, all species decreased in biomass with increasing Mo supply. Selenium did not impact biomass at the supplied levels. All Astragali accumulated Mo upwards of 0.1% of dry weight. Selenium levels were up to 0.08% in Astragalus racemosus and 0.04% Se in the other species. Overall, there was no correlation between Se hyperaccumulation and Mo accumulation capacity. However, the hyperaccumulators and nonaccumulators differed in some respects. While none of the species had a higher tissue Mo to sulfur (S) ratio than the growth medium, nonaccumulators had a higher Mo/S ratio than hyperaccumulators. Also, while molybdate and selenate reduced S accumulation in nonaccumulators, it did not in hyperaccumulators. Furthermore, A. racemosus had a higher Se/S ratio than its medium, while the other species did not. Additionally, Mo and Se treatment affected S levels in nonaccumulators, but not in hyperaccumulators. In conclusion, there is no evidence of a link between Se and Mo accumulation and tolerance in Astragalus. Sulfate transporters in hyperaccumulating Astragali appear to have higher sulfate specificity over other oxyanions, compared to nonaccumulators, and A. racemosus may have a transporter with enhanced selenate specificity relative to sulfate or molybdate.
一些物种能够超积累硒（Se），其含量超过干重的0.1%。本研究探讨了硒超积累植物是否也能积累并耐受更多的钼（Mo）。一项实地调查显示，三种超积累黄芪属植物中的钼含量平均比三种非积累黄芪属植物高2倍，不过差异并不显著。接下来，进行了一项对照研究，将超积累植物总状黄芪（Astragalus racemosus）和二槽黄芪（Astragalus bisulcatus）与非积累植物德拉蒙德氏黄芪（Astragalus drummondii）和铃花黄芪（Astragalus convallarius）进行比较，观察它们在单独或存在硒的情况下对钼的积累和耐受性。当在含有0、12、24或48 mg/L钼酸盐和/或0、1.6或3.2 mg/L硒酸盐的琼脂培养基上生长时，所有物种的生物量都随着钼供应量的增加而减少。在所供应的水平下，硒对生物量没有影响。所有黄芪属植物积累的钼含量都超过干重的0.1%。总状黄芪中的硒含量高达0.08%，其他物种中的硒含量为0.04%。总体而言，硒的超积累与钼的积累能力之间没有相关性。然而，超积累植物和非积累植物在某些方面存在差异。虽然没有一个物种的组织钼硫（S）比高于生长培养基，但非积累植物的钼/硫比高于超积累植物。此外，虽然钼酸盐和硒酸盐会降低非积累植物中的硫积累，但对超积累植物却没有影响。此外，总状黄芪的硒/硫比高于其培养基，而其他物种则不然。另外，钼和硒处理会影响非积累植物中的硫水平，但对超积累植物没有影响。总之，没有证据表明黄芪属植物中硒和钼的积累与耐受性之间存在联系。与非积累植物相比，超积累黄芪属植物中的硫酸盐转运蛋白似乎对其他含氧阴离子具有更高的硫酸盐特异性，并且总状黄芪可能具有相对于硫酸盐或钼酸盐而言对硒酸盐特异性增强的转运蛋白。
