Plant power

2019-03-07 08:08:01

By Andy Coghlan FUNGI that cause crop diseases could one day be fooled into killing themselves, say researchers in the US. This might be possible either by spraying plants with substances that trigger fungal suicide, or by equipping them with genes so they can make potent “suicide pills” themselves. The suggestion comes from researchers studying osmotin, an antifungal compound produced by tobacco plants. All plants make osmotin or variants of it, but these are not powerful enough to prevent severe fungal disease. However, if scientists knew exactly how osmotin works, they could tackle these diseases with souped-up versions of the natural fungicides. “What’s unknown is how these actually kill fungi,” says Paul Hasegawa of Purdue University in West Lafayette, Indiana. To find out more, Hasegawa and his colleagues Ray Bressan and Meena Narasimhan examined how osmotin attacks yeast. They identified a receptor that osmotin binds to on the tough, outer wall of yeast. Narasimhan says that the receptor is a glycoprotein, a protein whose surface is covered with protruding strands of sugary polymer. Having anchored itself to one of these sugars, osmotin squeezes through the cell wall to reach the softer plasma membrane underneath. Here, by binding to an as-yet unidentified protein, it sends a molecular signal into the nucleus of the yeast ordering it to commit suicide through programmed cell death or “apoptosis”. Bressan reported the findings last week at a meeting of the Chinese National Academy of Sciences in Shanghai. The team is confident that the relevant receptors on harmful fungi are similar to that on yeast. They are now focusing on Fusarium oxysporum, a fungus that causes a major disease of corn called vascular wilt. “The next step is to find the equivalent binding receptor in the cell wall of Fusarium,