Parasitic Plant Has Flexible Detection Strategy For Finding Its Dinner

Purple witchweed is a nefarious predator in Africa. Each year the parasitic plant devours billions of dollars’ worth of rice, sorghum, millet, and sugarcane crops by sniffing out chemicals released into the soil by the unsuspecting crops. These chemicals—a family of diverse hormones called strigolactones—are produced by many plants to recruit symbiotic root fungi. The strigolactones also activate germination of purple witchweed seeds, and the resulting parasitic seedlings rob their prey of nutrients. Researchers have wondered how purple witchweed can sniff out a variety of plants when they don’t all employ the same strigolactones. A team led by the University of Toronto’s Peter McCourt has the answer: Using X-ray crystallography, the researchers found that the parasite’s strigolactone receptor binding pocket is much larger than that found in other plants’ strigolactone receptors, including that of Arabidopsis plants, which are often used as a model plant (Science 2015, DOI: 10.1126/science.aac9476). The bigger binding pocket widens the range of strigolactones purple witchweed can detect and thus expands its range of possible prey. The work could provide inspiration for those developing strategies to curb the plant parasite.