Abstract
Strigolactones (SLs) are a class of plant hormones that play several roles in plants, such as suppressing shoot branching and promoting arbuscular mycorrhizal symbiosis. The positive regulation of plant disease resistance by SLs has recently been demonstrated by analyses using SL-related mutants. In Arabidopsis, SL-mediated signaling has been reported to modulate salicylic acid-mediated disease resistance, in which the priming of plant immunity plays an important role. In this study, we analyzed the effect of the synthetic SL analogue rac-GR24 on resistance against necrotrophic pathogen Botrytis cinerea. In rac-GR24-treated plants, disease resistance against B. cinerea was enhanced in an ethylene- and camalexin-dependent manners. Expression of the ethylene-related genes and the camalexin biosynthetic gene and camalexin accumulation after pathogen infection were enhanced by immune priming in rac-GR24-treated plants. These suggest that SL-mediated immune priming is effective for many types of resistance mechanisms in plant self-defense systems.