Studies on the host recognition mechanism of root parasitic plants

Abstract

Among parasitic angiosperms, witchweeds (Striga spp.) and broomrapes (Orobanche and Phelipanche spp.) are the two most devastating root parasitic plants, causing enormous crop losses around the world. These root parasites have evolved special strategies to ensure their survival; the seeds germinate only when they are within the host rhizosphere so that after germination the seedlings can reach and parasitize the host roots. To locate host roots, root parasites exploit strigolactones (SLs), host-derived chemical signals that are released by host plants for symbiotic arbuscular mycorrhizal (AM) fungi. In addition to these functions as rhizosphere signaling molecules, SLs act as a class of plant hormones regulating shoot branching. Using high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS), SLs in root exudates from various plants have been characterized. During studies, in addition to the known SLs, more than 10 novel SLs have been isolated and their structures determined. Plants produce and exude mixtures of SLs, and nutrient availability affects SL production and exudation. These results suggest that quantitative and qualitative differences in SL production and/or exudation are important in host recognition of root parasitic plants. © Pesticide Science Society of Japan.