Abstract
Parasitic weeds are considered the most damaging agricultural agents in the developing world. To ensure a host plant is present for infection, parasitic plant only germinate when they sense a group of related compounds, called strigolactones that are released by the host root. Unfortunately, since strigolactones do not appear to regulate germination of experimentally tractable plants there is no coherent model of how these compounds function in parasitic seed. Here we show that strigolactones are both necessary and sufficient for a variety of light-related processes including germination in the model plant Arabidopsis. Light appears to stimulate strigolactone synthesis, which in turn stabilizes the key light response transcription factor HY5 and inhibits hypocotyl elongation. Our results suggest parasitic weeds may use strigolactones to substitute for light signaling during germination and early seedling growth, which should identify new approaches for breeding host resistance.
