July 15, 2008

Two Proteins Help Arsenic Absorption Through Rice

Although scientists have known that rice has the ability to absorb potentially harmful arsenic from the soil, they have previously been unable to describe how it works.

Now, scientists in Japan may have the answer.

Writing in the Proceedings of the National Academy of Sciences, Ma Jianfeng and colleagues of Okayama University's Research Institute for Bioresources said they have identified two proteins commonly found in rice plants that may be accountable for helping the crop transport arsenic from the soil to the grain.

"We used mutant paddy (in which) these two transporters were knocked out and we saw decreased arsenite in both the stalk and rice grain," said Ma.

In a separate study, Scandinavian researchers recently reported the discovery of a gene that fights off fungal infections and may also allow plant cells to absorb arsenite.

Arsenic can be found naturally in the environment, and although it has been beneficial in small amounts to cure diseases like syphilis, prolonged exposure to the element in drinking water has been linked to cancers of the lung, bladed and skin, numbness, cardiovascular disease and diabetes.

Arsenic-contaminated groundwater is commonly used for irrigating rice crops in places such as Bangladesh and West Bengal in India, resulting in arsenic accumulation in soils and grain.

Researchers noted that the two transporter proteins reduced absorption of silicon from the soil. Silicon occurs naturally and protects rice from pests and disease.

"Silicon concentration was also decreased. So in future we have to try to change the selectivity, to allow silicon to be transported but not arsenic. That's what we have to do in future," Ma said.

"Silicon and arsenic use the same transporters ... (using) more silicon fertilizers in paddy fields (will result in) more silicon uptake and less arsenic."


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