Laboratory of Biology and Biotechnology of Microorganisms, Environmental Microbiology and Toxicology Unit, Faculty of Sciences Semlalia, Cadi Ayyad University, PO Box 2390, Marrakech, Morocco.
Technische Universität Dresden, Institut für Genetik, Helmholtzstr. 10, D-01069, Dresden, Germany.
Environ Sci Pollut Res Int. 2016 May;23(10):10037-49. doi: 10.1007/s11356-016-6223-2. Epub 2016 Feb 11.
Irrigation of crops with microcystins (MCs)-containing waters-due to cyanobacterial blooms-affects plant productivity and could be a way for these potent toxins entering the food chain. This study was performed to establish whether MC-tolerant rhizobia could benefit growth, nodulation, and nitrogen metabolism of faba bean plants irrigated with MC-containing waters. For that, three different rhizobial strains-with different sensitivity toward MCs-were used: RhOF96 (most MC-sensitive strain), RhOF125 (most MC-tolerant strain), or Vicz1.1 (reference strain). As a control, plants grown without rhizobia and fertilized by NH4NO3 were included in the study. MC exposure decreased roots (30-37 %) and shoots (up to 15 %) dry weights in un-inoculated plants, whereas inoculation with rhizobia protects plants toward the toxic effects of MCs. Nodulation and nitrogen content were significantly impaired by MCs, with the exception of plants inoculated with the most tolerant strain RhOF125. In order to deep into the effect of inoculation on nitrogen metabolism, the nitrogen assimilatory enzymes (glutamine synthetase (GS) and glutamate synthase (GOGAT)) were investigated: Fertilized plants showed decreased levels (15-30 %) of these enzymes, both in shoots and roots. By contrast, inoculated plants retained the levels of these enzymes in shoots and roots, as well as the levels of NADH-GOGAT activity in nodules. We conclude that the microcystin-tolerant Rhizobium protects faba bean plants and improves nitrogen assimilation when grown in the presence of MCs.
用含有微囊藻毒素（MCs）的水灌溉作物——由于蓝藻水华——会影响植物的生产力，并可能成为这些强效毒素进入食物链的一种途径。本研究旨在确定耐 MC 根瘤菌是否可以促进用含有 MC 的水灌溉的蚕豆植物的生长、结瘤和氮代谢。为此，使用了三种不同的根瘤菌菌株：RhOF96（最敏感的 MC 菌株）、RhOF125（最耐 MC 的菌株）或 Vicz1.1（参考菌株）。作为对照，研究中还包括未接种根瘤菌但用 NH4NO3 施肥的植物。MC 暴露降低了未接种植物的根（30-37%）和地上部分（高达 15%）的干重，而接种根瘤菌可以保护植物免受 MC 毒性的影响。结瘤和氮含量受到 MCs 的显著损害，但接种最耐 MC 的菌株 RhOF125 的植物除外。为了深入研究接种对氮代谢的影响，研究了氮同化酶（谷氨酰胺合成酶（GS）和谷氨酸合酶（GOGAT））：施肥植物的这些酶的水平（地上部分和根部的 15-30%）降低。相比之下，接种植物在地上部分和根部保留了这些酶的水平，以及在根瘤中 NADH-GOGAT 活性的水平。我们得出结论，耐微囊藻毒素的根瘤菌可以保护蚕豆植物，并在存在 MCs 的情况下提高氮同化。
