Cooperation and Conflict in the Legume-Rhizobium Symbiosis

豆科植物-根瘤菌共生中的合作与冲突

• 批准号: 0077903
• 负责人: Robert Ford Denison
• 金额: $ 12.26万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-09-15 至 2002-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0077903&HistoricalAwards=false
• 关键词: Cooperation; Conflict; Legume; Rhizobium; Symbiosis

Legumes, such as clover, alfalfa, and soybean, are important in agricultureand in nature. Soil bacteria known as rhizobia can benefit legumes whenthey infect their roots, because they can take up atmospheric nitrogen andsupply it to the plant. This extra nitrogen increases plantphotosynthesis, thereby indirectly increasing the energy supply to therhizobia. Thus, symbiosis between legume and rhizobium seems beneficial toboth. But what if, as often happens, two or more different strains ofrhizobia infect the same plant? An initially rare strain that uses plantresources for its own reproduction, rather than for nitrogen fixation,could increase in numbers at the expense of both the plant and the morecooperative rhizobial strain. Although most rhizobia seem to bepredominantly beneficial, such "parasitic" strains do exist.This research will determine whether plant responses to rhizobia that failto fix nitrogen can select for more beneficial rhizobia. Previous researchshows that legumes can control the oxygen supply to rhizobia inside theirroot nodules. The PIs will determine how this oxygen supply changes withchanges in nitrogen fixation by rhizobia, and how this legume responseaffects the survival and reproduction of the rhizobia. Most of theresearch will be conducted under controlled laboratory conditions, but afield test will determine whether legumes alter the frequency ofcooperative vs. parasitic rhizobia in soil. In addition to possiblepractical applications in agriculture, the research will contribute tooverall understanding of the general problem of cooperation betweenspecies. Such cooperation is critical to the pollination of flowers, thesurvival and growth of coral reefs, plant growth in phosphorus-poor soils,and many other natural systems.

豆科植物，如三叶草、苜蓿和大豆，在农业和自然界中都很重要。被称为根瘤菌的土壤细菌感染豆科植物的根部时对豆科植物有益，因为它们可以吸收大气中的氮并将其供应给植物。这些额外的氮增加了植物的光合作用，从而间接增加了对根瘤菌的能量供应。因此，豆科植物和根瘤菌之间的共生似乎对双方都有益。但是，如果像经常发生的那样，两种或两种以上不同的根瘤菌感染了同一株植物呢？一种最初罕见的菌株，利用植物资源进行自身繁殖，而不是固氮，可能会以牺牲植物和更能合作的根瘤菌菌株为代价增加数量。虽然大多数根瘤菌似乎主要是有益的，但这种“寄生”菌株确实存在。本研究将确定植物对不能固氮的根瘤菌的反应是否可以选择更有益的根瘤菌。先前的研究表明，豆科植物可以控制根瘤内根瘤菌的氧气供应。pi将确定这种氧供应如何随着根瘤菌固氮的变化而变化，以及这种豆科植物的反应如何影响根瘤菌的生存和繁殖。大多数研究将在受控的实验室条件下进行，但田间试验将确定豆类是否会改变土壤中合作根瘤菌和寄生根瘤菌的频率。除了可能在农业上的实际应用外，这项研究还将有助于全面了解物种间合作的一般问题。这种合作对花朵的授粉、珊瑚礁的生存和生长、缺磷土壤中的植物生长以及许多其他自然系统都至关重要。