A few modifications in the genome turn a fungal plant pathogen into a potentially beneficial organism

Because of their sedentary life, plants have to make the most of their surroundings. To do so, they take advantage of hitherto unknown molecular mechanisms to determine what benefits them and what harms them. They also grant microorganisms access to their roots in exchange for essential nutrients in the soil. The soil fungus Colletotrichum tofieldiae serves the model plant Arabidopsis as such a subtenant when required. The plant accepts the fungus as a phosphate supplier in situations where it has no access to those minerals itself, but rejects the fungus if it is able to tap phosphate supplies on its own. Thus, the plant very accurately weighs the demands of its environment to which it must respond. In the process, the plant's immune system plays a key role. Stéphane Hacquard, Paul Schulze-Lefert and Richard O'Connell of the Max Planck Institute for Plant Breeding Research in Cologne are addressing the question of what changes are responsible for ensuring that Colletotrichum tofieldiae no longer has to contend with the full brunt of the plant's immune system under certain conditions. They have found that just a few changes in the genome are sufficient to turn a pathogen into a partner.