About This Project

Fertilizers used in agriculture have significant environmental effects like toxic algal blooms and biodiversity loss. Legumes are a crop with their own method of supplying nitrogen for growth: a symbiotic relationship with rhizobia. Rhizobia can convert atmospheric nitrogen into a form usable by plants, although not all rhizobia fix nitrogen. We hypothesize that by improving rhizobia’s ability to fix nitrogen we can offer an eco-friendly way to improve crop production.

Ask the Scientists

What is the context of this research?

Legumes have the unique ability to form a symbiotic relationship with nitrogen-fixing bacteria, Rhizobia. As a result, they require little to no fertilizer and are ideal for soil revitalization to grow other crops. Improving and expanding the benefits of rhizobia colonization can promote decreased fertilizer use while improving crop quality. Bean plants inoculated with rhizobia engineered to overexpress a gene tied to trehalose synthesis has been shown to increase nitrogen fixation, as well as increase crop yields and tolerance to environmental stressors. Trehalose is a sugar used by many organisms to survive freezing or droughts. This research will be used to develop the next generation of rhizobial inoculants and eventually improve plants beyond legumes.

What is the significance of this project?

The overuse of nitrogen-rich fertilizers causes massive ecological damage worldwide, such as toxic algal blooms, which can poison animals and humans, and dead zones, which are deoxygenated bodies of water that negatively affect marine life and even coral. Dead zones have the potential to greatly damage not only coastal ecosystems but also coastal economies. In 2015, the landings revenue of the Gulf of Mexico totaled $858 million, making it the fourth most profitable region nationwide that year. Reducing the need for nitrogenous fertilizers is critical for the development of an economically and ecologically sustainable future. Improving the success rates of rhizobia/legume symbiosis could be the first step in eliminating the need for expensive fertilizers and in building that future.

What are the goals of the project?

Overexpressing otsA (a gene responsible for trehalose biosynthesis) in rhizobia has been shown to improve the drought and frost resistance of the plant, and increase nitrogenase activity and crop yields. We will verify these findings by applying the Rhizobium strain overexpressing otsA (Ox) to Phaseolus vulgaris and examining its effect on nodule formation, biomass, and stress-resistance. Then we will determine whether Ox is beneficial to other types of legumes. This data will determine whether Ox benefits are species-specific or general. For legumes that do not respond to Ox, we will examine other trehalose-synthesis pathways to identify a new candidate gene to promote trehalose production. Our goal is to create the next generation of rhizobia inoculants that will improve plant growth.