Bacteria teach crops how to endure drought

BUGS IN one's body usually mean aches and pains, but researchers studying how some bacteria exist safely in the large intestine of humans by adapting to water-scarce conditions, may come up with clues to new varieties of drought-resistant crops that could flourish in arid regions.

J Gowrishankar and his research team at the Centre for Cellular and Molecular Biology, Hyderabad, have identified the mechanism by which Escherichia coli responds to water-deprivation. "By inserting the E coli genes that mediate this process into plants," says Gowrishankar, "it should be possible to enhance their ability to survive in dry environments."

E coli was chosen because it represents a simple yet effective model to study osmoregulation, the process by which cells adapt to water scarcity. Gowrishankar and his co-workers have found that in dry conditions, chemical substances called proline, betaine and glutamate accumulate within a cell and high concentration of these compounds enables water to be sucked into the cell from outside.

The rise in the level of each of the three compounds is controlled by a separate gene. In the case of glutamate, the relevant gene activates an enzyme, causing glutamate to be synthesised within the cell. On the other hand, proline and betaine are pumped into the cell from the surrounding environment, against the normal direction of flow.

Experiments carried out by Gowrishankar's group shows the activity of these genes is highly sensitive to the water content of the cell and can increase by a factor of almost 400 under dry conditions. Says Gowrishankar, "We are now trying to understand how the cell senses the lack of water and the mechanism by which this 'switching on' of the genes takes place."

The next step is to transfer genes involved in osmoregulation into a plant species and determine whether its properties can be modified. Gowrishankar is confident that this is possible in principle, but warns there are several technical difficulties that may take a few years to overcome. For example, the bacterial genes have to be modified before they can be expressed in plants. In bacteria, as opposed to plants, many of the genes with a related function work in close association with each other. The genes involved in the pump for uptake of betaine in E Coli are of this type. To express these genes in crops, they would have to be inserted into the plant separately and made to function independently of each other. But an optimistic Gowrishankar assures, "The procedure involved takes time and effort, but it can be done."