Molecular Parasitic Plant–Host Interactions

Throughout evolution, a wide number of organisms specialized in parasitizing plants. Plants are not exceptions; certain plant species evolved as parasites of their own kind. Parasitic angiosperms evolved at least 12 times and show various lifestyles. For example, facultative parasitic plants can complete their life cycle and produce seeds without hosts, whereas obligate parasitic plants totally rely on their hosts. Some obligate parasitic plants, such as broomrapes (Orobanche spp.), witchweeds (Striga spp.), and dodders (Cuscuta spp.), are major crop pathogens that cause severe and persistent damage in agriculture. During parasitism, series of molecular signals are emitted by nearby plants and perceived by parasitic plants. These stimuli are often essential for parasitic plants to germinate and/or undergo parasitic stages in the right place and at the right time. On the other hand, a growing body of evidence supports the idea that plant immunity programs can be activated by detection of molecules derived from parasitic plants. Here, we summarize the molecular interactions between parasitic plants and host plants, mainly obtained from studies on Orobanchaceae parasitic plants.