Identification of Protein Domain Contributes to Safer Food

Because receptors determine the difference between a healthy plant and a sick – or even dead – plant, good regulation is essential. That means ‘standby’ in the absence of germs, but being activated quickly upon infection.

20/05/09 Researchers at the University of Amsterdam (UvA) and the Wageningen University and Research Centre (UR) have identified the protein component responsible for regulating innate immunity in humans and animals. They furthermore discovered that comparable changes in this regulating mechanism lead to comparable disruptions in human and plant immune systems. Their findings, published this week in Science, will contribute to the development of foods less vulnerable to disease and, moreover, to a better understanding of human autoimmune disorders.

The immune system uses so-called receptors to recognise germs. Scientists already knew that receptor proteins in plants and animals (in everything from sea urchins to humans) have very similar structures. Changes in these receptors can lead to a weakened or, conversely, to an overactive immune system, resulting in various autoimmune disorders. Examples in humans include diseases like Crohn disease, sarcoidosis, gout and Blau syndrome. In plants, these mutations give rise to phenomena like ‘paranoid plants’ – where plants defend themselves against illusory pathogens.

The article by Frank Takken (UvA) and Wladimir Tameling (UR) discusses the molecular mechanism responsible for regulating these immune receptors in plants. Because these receptors determine the difference between a healthy plant and a sick – or even dead – plant, good regulation is essential. That means ‘standby’ in the absence of germs, but being activated quickly upon infection. Takken and Tameling previously discovered that the central domain of these large so-called multi-domain receptors takes the lead role in regulation. They show that this regulation mechanism is similar in both plant and human immune receptors.

The term ‘multi-domain receptor’ refers to a protein consisting of multiple modules, each with its own distinct function. The receptor is comparable to a fire alarm, with a smoke detector, a control unit to detect when the sensor is activated and an alarm bell. Each component has its own task, and the removal of one of those components means the device as a whole breaks down. The same is true for these proteins. They have a component ensuring that the pathogen is recognised (the smoke detector), another that encodes and conveys this information (control unit) and a third component that transmits the signal to other proteins, which then act to turn on a cell’s defence system (alarm bells).