DisplayTitle

Analysis of a Blumeria graminis-Secreted Lipase Reveals the Importance of Host Epicuticular Wax Components for Fungal Adhesion and Development

¹Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, SK S7N 5E2, Canada; ²National Research Council of Canada, Plant Biotechnology Institute, Saskatoon, SK S7N 0W9, Canada; ³Department of Plant Sciences, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8, Canada; ⁴State Key Laboratory of Agrobiotechnology, Department of Plant Pathology, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100094, P. R. China

The biotrophic powdery mildew fungus Blumeria graminis releases extracellular materials to the surface of fungal infection structures that facilitate anchoring them to hydrophobic plant surfaces prior to infection; however, the chemistry of fungal adhesives and the mechanism of adhesion remain largely unclear. Expressed sequence tag analysis led to identification of a secreted lipase, Lip1, from B. graminis. Expression of LIP1 is dramatically upregulated during the early stages of fungal development. Lip1, secreted to the surface of fungal cell walls, possesses lipolytic activity against a broad range of glycerides and releases alkanes and primary fatty alcohols from the epicuticular wax of wheat leaves. Of the epicuticular wax components released by Lip1 activity, long-chain alkanes are the most efficient cues for triggering appressorium formation. Pretreatment of wheat leaves with Lip1, thereby removing leaf surface wax, severely compromises components of fungal pathogenicity, including conidial adhesion, appressorium formation, and secondary hypha growth. Our data suggest that Lip1 activity releases cues from the host surface to promote pathogen development and infection.