Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2010
Publication Date: 5/17/2010
Citation: Pasapula, V., Shen, G., Kuppu, S., Paez-Valencia, J., Mendoza, M., Hou, P., Chen, J., Qui, X., Zhu, L., Zhang, X., Auld, D., Blumwald, E., Zhang, H., Gaxiola, R., Payton, P.R. 2010. Expression of an arabidopsis vacuolar H+-pyrophosphatase gene (AVP1) in cotton improves drought- and salt tolerance and increases fibre yield in the field conditions. Plant Biotechnology Journal. 8(5):1-12. Interpretive Summary: Abiotic stresses such as drought, salinity, and extreme temperatures are serious threats to modern agriculture. These stresses lead to a series of morphological, physiological, biochemical, and molecular changes in plants that adversely affect plant growth and productivity. Water deficit and salinity are the major limiting factors in plant productivity. The primary challenge facing scientists today is enhancing crop tolerance to drought and salt stress in order to maintain productivity on marginal land under water-limited conditions. Improvements in this area of food and fiber production will have an enormous impact on the economies of the semi-arid southwest in the US, as well as, marginal production regions around the world. Cotton is a vital agricultural commodity and multi-billion dollar industry that underpins US and global economies. An important renewable resource, cotton is the world’s leading natural fiber and second largest oilseed crop in production. The production, marketing, consumption, and trade of cotton-based products stimulate the economy with revenues in excess of $100 billion annually in the U.S., making cotton the No. 1 value-added crop. Cotton is grown on more than 10 million acres in the US, with the majority of production in America's semi-arid southwest, a region prone to the aforementioned problems of drought and saline soils. We have initiated efforts toward enhancing abiotic stress tolerance in cotton via genetic engineering. This results of the research reported here show that over-expression of a membrane-bound ion pump results increases both salt and drought tolerance in cotton, including production of more fiber under field conditions. This work represents the first step in the potential application of this gene in agriculture.
Technical Abstract: The Arabidopsis gene AVP1 encodes a vacuolar pyrophosphatase that functions as a proton pump on the vacuolar membrane. Overexpression of AVP1 in Arabidopsis, tomato and rice enhances plant performance under salt and drought stress conditions, because up-regulation of the type I H+-PPase from Arabidopsis may result in a higher proton electrochemical gradient, which facilitates enhanced sequestering of ions and sugars into the vacuole, reducing water potential and resulting in increased drought- and salt tolerance when compared to wild-type plants. Furthermore, overexpression of AVP1 stimulates auxin transport in the root system and leads to larger root systems, which helps transgenic plants absorb water more efficiently under drought conditions. Using the same approach, AVP1-expressing cotton plants were created and tested for their performance under high-salt and reduced irrigation conditions. The AVP1-expressing cotton plants showed more vigorous growth than wildtype plants in the presence of 200 mM NaCl under hydroponic growth conditions. The soil-grown AVP1-expressing cotton plants also displayed significantly improved tolerance to both drought and salt stresses in greenhouse conditions. Furthermore, the fibre yield of AVP1-expressing cotton plants is at least 20% higher than that of wild-type plants under dry-land conditions in the field. This research indicates that AVP1 has the potential to be used for improving crop’s drought- and salt tolerance in areas where water and salinity are limiting factors for agricultural productivity.