Code-breaking in rice

A report from the University of California, Davis supplies further evidence that, while we humans might be fascinated by the world of espionage and counter-intelligence, we are not alone in finding it necessary to intercept and decode signals that might threaten our existence.

UC Davis specialises in researching problems relating to the production of rice, a staple food for over half the world’s population. A team of scientists recently investigated a biological signal that not only helps invading bacteria communicate with each other but also aids the targeted rice plants to co-ordinate their defence mechanisms.

Scientists already knew that the two major groups of bacteria, Gram-positive and Gram-negative, use distinctly different communication codes but this new signal does not fit into either system. A protein, Ax21, made inside the bacterial cell, is processed to generate a signal that causes the colony of bacteria to assemble themselves into elaborate protective modes when it reaches a certain threshold. This makes them resistant to drying out and antibiotic treatment. It appears that Ax21 is also involved in transforming the bacteria from benign organisms into dangerous invaders.

Some rice plants carry an immune receptor, XA21, which intercepts the Ax21 signal and, by alerting the plant’s defence response, may give it a tactical advantage in its battle to survive. The researchers also found Ax21 in at least one human pathogen, a finding that could lead to new ways to combat infection in humans as well as plants.