title: Magnaporthe grisea cutinase2 mediates appressorium differentiation and host penetration and is required for full virulence.
abstract: The rice blast fungus Magnaporthe grisea infects its host by forming a specialized infection structure, the appressorium, on the plant leaf. The enormous turgor pressure generated within the appressorium drives the emerging penetration peg forcefully through the plant cuticle. Hitherto, the involvement of cutinase(s) in this process has remained unproven. We identified a specific M. grisea cutinase, CUT2, whose expression is dramatically upregulated during appressorium maturation and penetration. The cut2 mutant has reduced extracellular cutin-degrading and Ser esterase activity, when grown on cutin as the sole carbon source, compared with the wild-type strain. The cut2 mutant strain is severely less pathogenic than the wild type or complemented cut2/CUT2 strain on rice (Oryza sativa) and barley (Hordeum vulgare). It displays reduced conidiation and anomalous germling morphology, forming multiple elongated germ tubes and aberrant appressoria on inductive surfaces. We show that Cut2 mediates the formation of the penetration peg but does not play a role in spore or appressorium adhesion, or in appressorial turgor generation. Morphological and pathogenicity defects in the cut2 mutant are fully restored with exogenous application of synthetic cutin monomers, cAMP, 3-isobutyl-1-methylxanthine, and diacylglycerol (DAG). We propose that Cut2 is an upstream activator of cAMP/protein kinase A and DAG/protein kinase C signaling pathways that direct appressorium formation and infectious growth in M. grisea. Cut2 is therefore required for surface sensing leading to correct germling differentiation, penetration, and full virulence in this model fungus.
authors: Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom.
authors: Pari
authors: P
authors: Skamnioti
authors: Sarah J
authors: SJ
authors: Gurr
mesh_terms: D000268:Adhesiveness / Q000187:drug effects; D002265:Carboxylic Ester Hydrolases / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology; D056229:Fungal Structures / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005800:Genes, Fungal; D006790:Host-Parasite Interactions / Q000187:drug effects; D057927:Hydrophobic and Hydrophilic Interactions; D020082:Magnaporthe / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity* / Q000648:ultrastructure; D008563:Membrane Lipids / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D012275:Oryza / Q000187:drug effects / Q000382:microbiology*; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology; D011433:Propranolol / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014774:Virulence / Q000187:drug effects; D014970:Xanthines / Q000494:pharmacology
chemical_list: D004075:Diglycerides; D008563:Membrane Lipids; D012333:RNA, Messenger; D014970:Xanthines; C000521:cutin; D011433:Propranolol; D000242:Cyclic AMP; D002265:Carboxylic Ester Hydrolases; C019952:cutinase
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