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Abstract

Fungi-induced plant diseases affect global food security and plant
ecology. The biotrophic fungus Ustilago maydis causes smut disease in
maize (Zea mays) plants by secreting numerous virulence effectors that
reprogram plant metabolism and immune responses(1,2). The secreted
fungal chorismate mutase Cmu1 presumably affects biosynthesis of the
plant immune signal salicylic acid by channelling chorismate into the
phenylpropanoid pathway(3). Here we show that one of the 20
maize-encoded kiwellins (ZmKWL1) specifically blocks the catalytic
activity of Cmu1. ZmKWL1 hinders substrate access to the active site of
Cmu1 through intimate interactions involving structural features that
are specific to fungal Cmu1 orthologues. Phylogenetic analysis suggests
that plant kiwellins have a versatile scaffold that can specifically
counteract pathogen effectors such as Cmu1. We reveal the biological
activity of a member of the kiwellin family, a widely conserved group of
proteins that have previously been recognized only as important human
allergens.