Overexpression of a Cytochrome P450 Monooxygenase Involved in Orobanchol Biosynthesis Increases Susceptibility to Fusarium Head Blight.

Fusarium Head Blight (FHB) is a cereal disease caused primarily by the ascomycete fungus with public health issues due to the production of mycotoxins including deoxynivalenol (DON). Genetic resistance is an efficient protection means and numerous quantitative trait loci have been identified, some of them related to the production of resistance metabolites. In this study, we have functionally characterized the gene encoding a cytochrome P450 monooxygenase (CYP). We showed that belongs to an oligogenic family of five members. However, following infection by , is the only copy strongly transcriptionally induced in a DON-dependent manner. The BdCYP711A29 protein is homologous to the MAX1 and MAX1-like CYPs representing key components of the strigolactone biosynthesis. We show that BdCYP711A29 is likely involved in orobanchol biosynthesis. Alteration of the sequence or expression alone does not modify plant architecture, most likely because of functional redundancy with the other copies. lines overexpressing exhibit an increased susceptibility to , although no significant changes in defense gene expression were detected. We demonstrate that both orobanchol and exudates of overexpressing lines stimulate the germination of macroconidia. We therefore hypothesize that orobanchol is a susceptibility factor to FHB.