Bacteria plays an important role in a plant’s immunity

Washington, Nov 28 ( When it comes to plants’ innate immunity, bacteria play a vital role, according to researchers.

A receptor molecule in the plant pairs up with a specific molecule on the invading bacteria and, presto, the immune system swings into action to defend against the invasion of the disease-causing microbe.

Scientists at the University of California, Davis (UC-D) have identified the bacterial signalling molecule that matches up with a specific receptor in rice plants to ward off a devastating disease known as bacterial blight of rice.

“The new discovery of this bacterial signalling molecule helps us better understand how the innate immune system operates,” says UC-D plant pathologist Pamela Ronald.

“Because similar pairs of receptors and bacterial signalling molecules are known to exist in other plants also, as well as animals and humans, we are hopeful that this work will lead to new strategies for controlling diseases in plants and people,” she said.

In 1995, Ronald’s lab identified the XA21 gene. Subsequent discoveries revealed that receptors with striking structural similarities to the XA21 receptor protein exist in other plants, flies, mice and even humans.

These receptors were later named pattern recognition receptors (PRRs) because they have the ability to recognise molecules that occur across species in a large class of disease-causing microbes, a UC-D release said.

These receptors can then launch a protective immune defence on behalf of the plant or animal. Together, PRRs and the microbial molecules they recognise comprise a previously unknown system of immunity called innate immunity, built into the genetic makeup of the plant. Unlike animals, plants do not produce antibodies.

These findings were published in the November issue of Science.