Unlocking rice immune system will benefit humanity: Scientists

Rice is a staple food for half of the world's population. To protect it against deadly pathogens, a team of researchers has identified a bacterial signal that, when recognised by rice plants, enables them resist a devastating blight disease.

The team discovered that a bacterial protein called "RaxX" activates a specific rice immune receptor protein named "XA21".

This activation triggers an immune response against Xanthomonas oryzaepv.oryzae (Xoo), a pathogen that causes bacterial blight, a serious disease of rice crops.

"Our results show that 'RaxX' - a small, previously undescribed bacterial protein - is required for activation of immunity to Xoo," said Pamela Ronald, plant geneticist for the US Department of Energy (DOE)'s Joint BioEnergy Institute (JBEI) and the University of California (UC) Davis.

XA21 can detect RaxX and quickly mobilise its defenses to mount a potent immune response against Xoo.

"Rice plants that do not carry the XA21 immune receptor or other related immune receptors are virtually defenseless against bacterial blight," Ronald added in a paper that appeared in the journal Science Advances.

Pathogens of grass-type biofuel crops that would reduce the yield of fuel-producing biomass likely use similar infection mechanisms to Xoo.

"Having identified the activator of XA21, we will be able to study the rice immune system in far greater detail than ever before. This might help in the future engineering of more disease-resistant grass-type biofuel crops," explained Benjamin Schwessinger, a grass geneticist with JBEI.

Most plants and many animals can only defend themselves against a given disease if they carry specialised immune receptors that sense the invading pathogen behind the disease.

Rice is also a model plant for perennial grasses which are prime feedstock candidates for the production of clean, green and renewable cellulosic biofuels.

Just as bacterial blight poses a major threat to rice crops, bacterial infections of grass-type fuel plants could present major problems for the future production of advanced biofuels.

In addition to its implications for future grass-type biofuel feedstocks, unlocking the rice immune system also holds important implications for the worldwide supply of rice, the authors concluded.