A fungal effector suppresses plant immunity by manipulating DAHPS-mediated metabolic flux in chloroplasts.

ABSTRACT

Plant secondary metabolism represents an important and ancient form of defense against pathogens. Phytopathogens secrete effectors to suppress plant defenses and promote infection. However, it is largely unknown, how fungal effectors directly manipulate plant secondary metabolism. Here, we characterized a fungal defense-suppressing effector CfEC28 from Colletotrichum fructicola. Gene deletion assays showed that ∆CfEC28-mutants differentiated appressoria normally on plant surface but were almost nonpathogenic due to increased number of plant papilla accumulation at attempted penetration sites. CfEC28 interacted with a family of chloroplast-localized 3-deoxy-d-arabinose-heptulonic acid-7-phosphate synthases (DAHPSs) in apple. CfEC28 inhibited the enzymatic activity of an apple DAHPS (MdDAHPS1) and suppressed DAHPS-mediated secondary metabolite accumulation through blocking the manganese ion binding region of DAHPS. Dramatically, transgene analysis revealed that overexpression of MdDAHPS1 provided apple with a complete resistance to C. fructicola. We showed that a novel effector CfEC28 can be delivered into plant chloroplasts and contributes to the full virulence of C. fructicola by targeting the DAHPS to disrupt the pathway linking the metabolism of primary carbohydrates with the biosynthesis of aromatic defense compounds. Our study provides important insights for understanding plant-microbe interactions and a valuable gene for improving plant disease resistance.