Natural protein in rice helps keep arsenic out in grains

Copyright: GMB Akash / Panos

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  • The protein, OsABCC1, lives in the roots, leaves and other organs of rice plants
  • OsABCC1 averts arsenic from damaging plant tissue by moving it into vacuoles
  • The study opens potentials for breeding rice in new ways and promoting wild rice

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[HANOI] Researchers have discovered a natural mechanism in rice plants that restricts the transfer of arsenic in soils to the rice grain by sequestering it in pocket-like cell membranes called vacuoles, opening scientific potentials for rice-producing nations across the developing world.

The study, published in the Proceedings of the National Academy of Sciences (PNAS) on 20 October, found that a transporter protein called OsABCC1 lives in the roots, leaves and other organs of a rice plant. Removing it caused the amount of arsenic in the grains of a rice plant to rise more than fivefold.

The study marks the first time any transporter has been identified in the process of vacuolar sequestration of arsenic toxin in rice plants.

“It’s quite a neat piece of work,” Steve McGrath, an arsenic expert at Rothamsted Research in Britain, tells SciDev.Net about the research study.

“It’s a first step and one particular strategy to decrease arsenic in grain,” he notes. “There may be other transporters throughout the plant that can do things and be switched off or turned down, or whatever mechanism you can think of to achieve similar results.”

In the 1990s, there was a flurry of interest in arsenic contamination of groundwater, but it was not until last year, McGrath says, that scientists had “fairly clear evidence” of how arsenic concentration in food affected human health.

People who are repeatedly exposed to arsenic in soils and water are at risk for a range of diseases, including cancer, the study reported. The problem is “particularly serious” in South Asia and around the Mekong area of South-East Asia where groundwater containing high concentrations of arsenic is used both for drinking water and irrigating rice.

Rice accumulates more arsenic in its shoots and grains than wheat, barley and other cereal crops. That could be because rice grows in flooded conditions where arsenic can proliferate, and because rice plants have a more efficient uptake system for the poison.
“This is a serious problem because rice is a staple food for Asian countries,” adds Jian Feng Ma, a researcher at Japan’s Okayama University and one of the study’s authors.

Jian tells SciDev.Net that the study could have two main applications: breeding rice in a way that would “over express” the OsABCC1 transporter, or identifying and promoting wild rice varieties in which it is especially active.

McGrath, however, says the first approach would be unusual because scientists typically modify the genetic structures of plants to make them more resistant to pests, not to make them healthier for human consumption.

“It’s a test, if you like, of the public’s and legislators’ opinion” about genetic engineering in plants, he says. “Is this more acceptable because it’s having a direct health benefit?”

Link to full paper in Proceedings of the National Academy of Sciences

This article has been produced by SciDev.Net's South-East Asia & Pacific desk.


PNAS doi: 10.1073/pnas.1414968111 (2014)