Relevant Publications
As global warming becomes an imminent reality, solutions to its harmful effects are needed sooner than ever. One of the most essential aspects to civilization, affected by global warming, is our agriculture. Drought conditions all across the globe are causing hardship to crops and food shortages in parts of the world. Furthermore, as the global population increases, increased crop productivity and expanded areas of cultivation are needed. The meet the needs of this growing population it is important to find ways to utilize marginal soils, typically due to high salt concentrations, for cultivation of crops.
Leguminous plants such as soybeans are a particularly attractive crop because of their symbiotic association with nitrogen-fixing bacteria which reduces the need for nitrogen fertilizer application. However, crops such as soybean are not well suited for drought stricken areas or marginal soils. The primary complication for these types of soils in the regions with drought is the impact of low water activity. Low water activity due to drought or high salt concentrations result in similar effects on the plant. Due to osmosis, this can cause the plants’ cells to lose water and shrivel up, thereby becoming useless and killing the plants. Drought also affects the bacteria that associate with plant roots, particularly nitrogen-fixing symbionts of legume plants. Because the osmotic effect of drought and high salt concentrations are similar, a single approach can be used to address both problems. This project will use genes found in naturally salt tolerant organisms to increase the salt/drought tolerance of Bradyrhizobium japonicum the nitrogen fixing symbiont of soybean.
Naturally salt tolerant bacteria can be found in variety of habitants. Depending on the level of salt in the environment, these bacteria will employ different strategies to combat osmotic stress. The most common approach is to take up or synthesize compatible solutes such as glycine-betaine. Introducing compatible solutes into the cytoplasm of the cells counteracts high salt concentration outside the cell without interfering with the normal function of cellular enzymes which may be inhibited by salts. The research group of Dr. Mei-Chin Lai at the National Chung-Hsing University in Taiwan has cloned the betaine biosynthetic genes from a marine bacterium, Methanohalophilus portucalensis FDF1T, and introduced them into Escherichia coli and into the model plant Arabidopsis thaliana. In each case, her group has demonstrated increased levels of salt tolerance. Therefore, it is feasible that introducing these same genes into B. japonicum will increase the salt tolerance of the organism. B. japonicum is naturally very sensitive to salt and generally will not grow at salt concentrations as low as 0.5%. Therefore, increasing salt tolerance should have a significant impact on the utility of this organism in more extreme conditions.
The project would let agriculture be introduced to drier, saltier areas of the planet. This will allow more crops to be grown and food to be made because they can survive in drought and high salt conditions. The goal of my project is to develop successful salt tolerant strains of B. japonicum that would protect crops. The success of this project would bring about many positive changes to agriculture and the world.
