Evolution of strigolactone perception by seeds of parasitic plants: reinventing the wheel

The root-parasitic plants of the witchweed family (Orobanchanceae) produce seeds that are adapted to germinate in response to strigolactones (SLs) exuded from the roots of their host plants. The resulting colonization of crops such as maize and sorghum by these parasites can cause massive losses in production and to the livelihoods of farmers (Westwood et al., 2010). The bewitching process, which brings the host under the control of the parasite, is elicited by the detection of trace amounts of SL in the vicinity of the host roots. New results published in three Science papers (Conn et al., 2015; Toh et al., 2015; Tsuchiya et al., 2015) have now determined that these parasites contain multiple putative SL receptors but, surprisingly, they may not have made use of the recognized SL receptor for this purpose. Instead, the proposed receptors have evolved by duplication and diversification of a gene encoding a putative receptor that responds to an unidentified SL-like signal and is known to trigger seed germination in Arabidopsis (Figure 1).