title: Claviceps purpurea expressing polygalacturonases escaping PGIP inhibition fully infects PvPGIP2 wheat transgenic plants but its infection is delayed in wheat transgenic plants with increased level of pectin methyl esterification.
abstract: Claviceps purpurea is a biotrophic fungal pathogen of grasses causing the ergot disease. The infection process of C. purpurea on rye flowers is accompanied by pectin degradation and polygalacturonase (PG) activity represents a pathogenicity factor. Wheat is also infected by C. purpurea and we tested whether the presence of polygalacturonase inhibiting protein (PGIP) can affect pathogen infection and ergot disease development. Wheat transgenic plants expressing the bean PvPGIP2 did not show a clear reduction of disease symptoms when infected with C. purpurea. To ascertain the possible cause underlying this lack of improved resistance of PvPGIP2 plants, we expressed both polygalacturonases present in the C. purpurea genome, cppg1 and cppg2 in Pichia pastoris. In vitro assays using the heterologous expressed PGs and PvPGIP2 showed that neither PG is inhibited by this inhibitor. To further investigate the role of PG in the C. purpurea/wheat system, we demonstrated that the activity of both PGs of C. purpurea is reduced on highly methyl esterified pectin. Finally, we showed that this reduction in PG activity is relevant in planta, by inoculating with C. purpurea transgenic wheat plants overexpressing a pectin methyl esterase inhibitor (PMEI) and showing a high degree of pectin methyl esterification. We observed reduced disease symptoms in the transgenic line compared with null controls. Together, these results highlight the importance of pectin degradation for ergot disease development in wheat and sustain the notion that inhibition of pectin degradation may represent a possible route to control of ergot in cereals.
authors.affiliation: Dipartimento di Scienze e tecnologie per l'Agricoltura, le Foreste, la Natura e l'Energia (DAFNE), Università della Tuscia, Via S. Camillo de Lellis snc, 01100 Viterbo, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Volpi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Raiola
authors.forename: Michela
authors.initials: M
authors.lastname: Janni
authors.forename: Anna
authors.initials: A
authors.lastname: Gordon
authors.forename: Donal M
authors.initials: DM
authors.lastname: O'Sullivan
authors.forename: Francesco
authors.initials: F
authors.lastname: Favaron
authors.forename: Renato
authors.initials: R
authors.lastname: D'Ovidio
mesh_terms: D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors / Q000235:genetics; D002967:Claviceps / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D060467:Disease Resistance / Q000235:genetics*; D004951:Esterification; D017343:Genes, Plant; D010368:Pectins / Q000378:metabolism*; D027805:Phaseolus / Q000235:genetics* / Q000378:metabolism; D010843:Pichia; D010935:Plant Diseases / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011096:Polygalacturonase / Q000037:antagonists & inhibitors* / Q000235:genetics; D014908:Triticum / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology
chemical_list: C081479:PGIP protein, plant; D010940:Plant Proteins; D010368:Pectins; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase; D011096:Polygalacturonase
keywords: CWDEs; Claviceps purpurea; Ergot disease; GalA; HD; HG; NS; PG; PGIP; PMEI; Pectin methyl esterification; Polygalacturonase; Polygalacturonase inhibiting protein; Transgenic plants; Wheat; cell wall degrading enzymes; galacturonic acid; homogalacturonan; honeydew; null segregant; pectin methyl esterase inhibitor; polygalacturonase; polygalacturonase inhibiting protein