Preiner Julian, Wienkoop Stefanie, Weckwerth Wolfram, Oburger Eva
Division of Molecular Systems Biology, Department of Ecogenomics and Systems Biology, University of Vienna, Vienna, Austria.
Department of Forest and Soil Sciences, Institute of Soil Research, University of Natural Resources and Life Sciences Vienna, Tulln, Austria.
Front Plant Sci. 2019 Apr 2;10:367. doi: 10.3389/fpls.2019.00367. eCollection 2019.
Tungsten (W) finds increasing application in military, aviation and household appliance industry, opening new paths into the environment. Since W shares certain chemical properties with the essential plant micronutrient molybdenum (Mo), it is proposed to inhibit enzymatic activity of molybdoenzymes [e.g., nitrate reductase (NR)] by replacing the Mo-ion bound to the co-factor. Recent studies suggest that W, much like other heavy metals, also exerts toxicity on its own. To create a comprehensive picture of tungsten stress, this study investigated the effects of W on growth and metabolism of soybean (), depending on plant nitrogen regime [nitrate fed (N fed) vs. symbiotic N fixation (N fix)] by combining plant physiological data (biomass production, starch and nutrient content, N fixation, nitrate reductase activity) with root and nodule proteome data. Irrespective of N regime, NR activity and total N decreased with increasing W concentrations. Nodulation and therefore also N fixation strongly declined at high W concentrations, particularly in N fix plants. However, N fixation rate (g N fixed g nodule dwt) remained unaffected by increasing W concentrations. Proteomic analysis revealed a strong decline in leghemoglobin and nitrogenase precursor levels (NifD), as well as an increase in abundance of proteins involved in secondary metabolism in N fix nodules. Taken together this indicates that, in contrast to the reported direct inhibition of NR, N fixation appears to be indirectly inhibited by a decrease in nitrogenase synthesis due to W induced changes in nodule oxygen levels of N fix plants. Besides N metabolism, plants exhibited a strong reduction of shoot (both N regimes) and root (N fed only) biomass, an imbalance in nutrient levels and a failure of carbon metabolic pathways accompanied by an accumulation of starch at high tungsten concentrations, independent of N-regime. Proteomic data (available via ProteomeXchange with identifier PXD010877) demonstrated that the response to high W concentrations was independent of nodule functionality and dominated by several peroxidases and other general stress related proteins. Based on an evaluation of several W responsive proteotypic peptides, we identified a set of protein markers of W stress and possible targets for improved stress tolerance.
钨（W）在军事、航空和家用电器行业中的应用日益广泛，这使其进入环境的途径增多。由于钨与植物必需的微量营养元素钼（Mo）具有某些化学特性，有人提出它会通过取代与辅因子结合的钼离子来抑制钼酶的酶活性[如硝酸还原酶（NR）]。最近的研究表明，钨与其他重金属一样，自身也具有毒性。为全面了解钨胁迫情况，本研究通过结合植物生理数据（生物量生产、淀粉和养分含量、固氮、硝酸还原酶活性）以及根和根瘤蛋白质组数据，研究了钨对大豆生长和代谢的影响，该影响取决于植物的氮素供应方式[供应硝酸盐（N供应）与共生固氮（N固定）]。无论氮素供应方式如何，随着钨浓度的增加，硝酸还原酶活性和总氮含量均下降。在高钨浓度下，根瘤形成以及固氮作用均显著下降，尤其是在N固定植物中。然而，固氮率（每克根瘤干重固定的氮克数）不受钨浓度增加的影响。蛋白质组学分析显示，豆血红蛋白和固氮酶前体水平（NifD）大幅下降，同时N固定根瘤中参与次生代谢的蛋白质丰度增加。综合来看，这表明与报道的对硝酸还原酶的直接抑制作用不同，固氮作用似乎是由于钨导致N固定植物根瘤氧水平变化，进而使固氮酶合成减少而受到间接抑制。除了氮代谢外，植物地上部分（两种氮素供应方式下）和地下部分（仅在N供应时）的生物量均大幅减少，养分水平失衡，碳代谢途径受阻，在高钨浓度下淀粉积累，且这些情况与氮素供应方式无关。蛋白质组学数据（可通过ProteomeXchange获取，标识符为PXD010877）表明，对高钨浓度的响应与根瘤功能无关，主要由几种过氧化物酶和其他一般应激相关蛋白主导。基于对几种钨响应蛋白型肽段的评估，我们确定了一组钨胁迫的蛋白质标志物以及提高胁迫耐受性的可能靶点。
