Engineering disease resistance in plants

What is it about?

Plants must manage the balance between fighting off organisms that cause disease (pathogens) and tolerating organisms that confer benefits (symbiotic microbes). How plants react to these two types of organisms is poorly understood, but it is thought that both pathogens and symbiotic microbes use the same pathways in the host plant in order to become established and grow. Plants have evolved mechanisms that enable them to recognise and accommodate symbiotic microbes – and pathogens are likely relying on some of these mechanisms in order to infect the plant and ultimately cause disease. However, the plant genes involved in these common mechanisms are not known, and research has been hampered because of a lack of a model plant suitable for studying both pathogenic and symbiotic relationships. A NEW MODEL INTERACTION The researchers examined the newly established model interaction between Phytophthora palmivora, an aggressive root-infecting pathogen, and Medicago truncatula, a legume plant. Fourteen genes in M. truncatula plants that are important for symbiotic relationships have been identified in previous studies. These genes were modified in M. truncatula plants, which were then inoculated with the pathogen P. palmivora, and the extent of infection was measured. The M. truncatula genes involved in pathogenic infection were identified and then compared to the previously identified genes involved in symbiosis. MANAGING THE BALANCE Seven out of 14 genes implicated in symbiosis were also found to be involved in pathogenic disease development. However, the researchers also found that five genes played different roles in symbiosis in comparison to their roles in pathogenic disease development. Therefore, plants might use these genes to manage the balance between defence from pathogens and tolerance of symbionts. THE ENGINEERING OF DISEASE-RESISTANT PLANTS This research is important as it will inform the genetic and biochemical engineering of disease-resistant plants and crops that are still able to retain their ability to form beneficial relationships with symbiotic organisms.

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