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: Chiara Volpi, Alessandro Raiola, Michela Janni, Anna Gordon, Donal M O'Sullivan, Francesco Favaron, Renato D'Ovidio
• Journal: Plant physiology and biochemistry : PPB (Plant Physiol Biochem) Vol. 73 Pg. 294-301 (Dec 2013) ISSN: 1873-2690 [Electronic] France
• PMID: 24184449 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Chemical References

• PGIP protein, plant
• Plant Proteins
• Pectins
• Carboxylic Ester Hydrolases
• pectinesterase
• Polygalacturonase

Topics

• Carboxylic Ester Hydrolases (antagonists & inhibitors, genetics)
• Claviceps (enzymology, genetics, metabolism, pathogenicity)
• Disease Resistance (genetics)
• Esterification
• Genes, Plant
• Pectins (metabolism)
• Phaseolus (genetics, metabolism)
• Pichia
• Plant Diseases (microbiology)
• Plant Proteins (genetics, metabolism)
• Plants, Genetically Modified
• Polygalacturonase (antagonists & inhibitors, genetics)
• Triticum (genetics, metabolism, microbiology)