Tuesday, 3 April 2012

Recent Advance in Genetics: nhaA Gene may increase rice yield in saline waters by Lucy Gramenz (42639820)

A major problem facing the global community today is global food security. With an ever-growing population the stress on agriculture to perform has never been higher. However, due to climate change and bad land management another factor has emerged; making achieving this goal even more difficult. Salinity. It disrupts natural ecosystems and has drastic effects on agriculture. 
Text Box: Figure 1 A Chinese Rice Field (SciDev 2005)Rice is one if not the most important crops globally. According to the FAO it supplies 35% to 69% of energy intake for Asia as well as 29% of energy consumption in all developing nations. With an increase of salinity and an increasing demand for rice, people are starting to wonder if rice is a sustainable crop for the future.  In china where approximately 8 percent of their rice fields have a high concentration of salt a recent research focus has been on reducing the effect of salinity on rice yields. Plants experience osmotic stress under saline conditions. In order for plants to grow normally homeostasis and intracellular pH must be controlled. Depending on the amount of salinity the crop is exposed to it can stunt growth or terminate the plant completely. A recent study injecting NhaA genes from Escherichia coli into rice has shown increased rice yields in high saline environments. NhaA is the gene that facilitates the Na+/H antiporter, which is responsible for exporting Na+ out of cells.  This scientific discovery may hold the key to combat the effects of salinity and feed the global rice demands.
There have been many genetic approaches towards securing the future food security however many of these studies have been directed at pest control and faster bigger plants. This study however has been one of the first to use genetic manipulation to combat salinity. The study was based around the antiporter gene NhaA. NhaA instructs the Na+/H+ antiporter to push out Na+ out of the cell when the cell is starting to experience stress from an unbalance Na+ concentration gradient.  The Na+/H+ antiporter’s role in the cell is the circulation of Na+ and H+ across both the outer membrane and the cytoplasmic membranes. It is key to maintain homeostasis and pH within the cell. NhaA is triggered when Na+ concentration in the cytoplasm becomes unmanageable by the cell. NhaA is then switched on and exports unnecessary Na+ out of the cell. 
NhaA genes from E. coli were able to be cloned and successfully transferred into the rice genome.  The new transgenic rice resulted in higher yields when exposed to higher concentration of salt compare to their non-transgenic counterparts.  Higher yields where due to better germination rates, growth rates and signs of ion compartmentalisation that enhance plant vacuoles ability to excrete Na+ from the cells.
Using the wonders of genetics scientists are now finding ways to adjust to a more saline environment. The importance of securing our global rice supply has never been so important.  Rice is the stable food for many different countries and culture but also the stable food for nations with the biggest populations like China and India.

Wu, L, Fan, Z, Guo, L, Li, Y, Chen, Z & Qu, L 2005, ‘Over-expression of the bacterial nhaA gene in rice enhances salt and drought tolerance’, Plant Science, vol. 168, pp. 297-302.

SciDev.net 2005, Gene for salt tolerance found in rice, viewed 19 March 2012, <http://www.scidev.net/en/news/gene-for-salt-tolerance-found-in-rice.html>


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