Gemperline Erin, Jayaraman Dhileepkumar, Maeda Junko, Ané Jean-Michel, Li Lingjun
Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA.
J Am Soc Mass Spectrom. 2015 Jan;26(1):149-58. doi: 10.1007/s13361-014-1010-0. Epub 2014 Oct 17.
Legumes have developed the unique ability to establish a symbiotic relationship with soil bacteria known as rhizobia. This interaction results in the formation of root nodules in which rhizobia thrive and reduce atmospheric dinitrogen into plant-usable ammonium through biological nitrogen fixation (BNF). Owing to the availability of genetic information for both of the symbiotic partners, the Medicago truncatula-Sinorhizobium meliloti association is an excellent model for examining the BNF process. Although metabolites are important in this symbiotic association, few studies have investigated the array of metabolites that influence this process. Of these studies, most target only a few specific metabolites, the roles of which are either well known or are part of a well-characterized metabolic pathway. Here, we used a multifaceted mass spectrometric (MS) approach to detect and identify the key metabolites that are present during BNF using the Medicago truncatula-Sinorhizobium meliloti association as the model system. High mass accuracy and high resolution matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) Orbitrap instruments were used in this study and provide complementary results for more in-depth characterization of the nitrogen-fixation process. We used well-characterized plant and bacterial mutants to highlight differences between the metabolites that are present in functional versus nonfunctional nodules. Our study highlights the benefits of using a combination of mass spectrometric techniques to detect differences in metabolite composition and the distributions of these metabolites in plant biology.
豆科植物已形成与被称为根瘤菌的土壤细菌建立共生关系的独特能力。这种相互作用导致根瘤的形成，根瘤菌在其中大量繁殖，并通过生物固氮（BNF）将大气中的双氮还原为植物可用的铵。由于两种共生伙伴的遗传信息都可获取，蒺藜苜蓿-苜蓿中华根瘤菌共生关系是研究生物固氮过程的极佳模型。尽管代谢物在这种共生关系中很重要，但很少有研究调查影响这一过程的代谢物种类。在这些研究中，大多数仅针对少数几种特定的代谢物，其作用要么是已知的，要么是已充分表征的代谢途径的一部分。在此，我们使用多方面的质谱（MS）方法，以蒺藜苜蓿-苜蓿中华根瘤菌共生关系作为模型系统，检测和鉴定生物固氮过程中存在的关键代谢物。本研究使用了高质量精度和高分辨率的基质辅助激光解吸/电离（MALDI）和电喷雾电离（ESI）轨道阱仪器，为更深入地表征固氮过程提供了互补的结果。我们使用了特征明确的植物和细菌突变体，以突出功能正常与功能异常的根瘤中存在的代谢物之间的差异。我们的研究强调了使用质谱技术组合来检测代谢物组成差异以及这些代谢物在植物生物学中的分布的好处。
