The isolation of a gene that confers salt tolerance in plants could lead to improved farming productivity in the Canadian prairies and many other areas of the world where crops are compromised by saline irrigation water, according to a study in the August 20 issue of Science.
The gene encodes a transport protein in plant cells whose activity allows plants to grow even in highly saline conditions. This protein, called the Na+/H+ antiport, prevents the sodium ions from salt from harming the cell and creates a balance of ions in the cell that draws water into the plant cell by osmosis.
"By successfully genetically engineering a plant to have this salt management system, we've opened up the possibility of modifying economically important crops so that they may grow in saline conditions," said Professor Eduardo Blumwald, who led the research group that discovered the gene in the University of Toronto's department of botany. Blumwald's collaborators were graduate students Gilad Aharon and Maris Apse and post-doctoral fellow Dr. Wayne Snedden.
"Since environmental stress due to salinity is one of the most serious factors limiting the productivity of crops, this innovation could have significant implications for the agricultural world," Blumwald said. In most crops the activity of the antiport transport system is very low. These plants cannot drive water into the cell in the presence of salt and instead lose water, causing reduced leaf size, a general decrease in growth, and ultimately death. Most commercial crops (corn, soybean, wheat, vegetables, fruits, etc.) experience a significant yield loss in saline soil.
Using Arabidopsis thaliana, a small salt-sensitive plant that grows rapidly, the researchers cloned the gene coding for the antiport and modified the plant to overproduce the antiport protein. Unlike other genetically modified plants, overproducing the antiport involves manipulating a protein already present as opposed to introducing a foreign protein not normally found in plants. The growth of the genetically engineered plants was compared to the growth of the normal plants as they were watered with increasing amounts of salt. The genetically modified plants showed sustained growth even when watered with high salt concentrations, while the normal plants progressively deteriorated with the addition of more salt.
Large regions of the Canadian prairies, the southwest United States, South America, Australia, Asia and Europe, which comprise 30 per cent of the world's irrigated land, have experienced serious declines in crop productivity in this century due to salinity. Approximately 10 million hectares are lost annually because of saline conditions. Irrigation water usually contains dissolved salts, and traditional solutions to this problem-- such as high-quality irrigation water and the installation of drainage systems-- are expensive and inaccessible in many areas. Attempts at conventional breeding to produce crops that adapt to the saline conditions have also been unsuccessful, with only a few varieties produced with low salt tolerance.
Worldwide patent applications have been filed on this discovery by the Innovations Foundation at U of T. Funding for the research was provided by the Natural Sciences and Engineering Research Council of Canada.
U of T Public Affairs
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