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The ThPG1 Endopolygalacturonase Is Required for the Trichoderma harzianum--Plant Beneficial Interaction

August 2009 , Volume 22 , Number  8
Pages  1,021 - 1,031

Eugenia Morán-Diez,1 Rosa Hermosa,1 Patrizia Ambrosino,2 Rosa E. Cardoza,3 Santiago Gutiérrez,3 Matteo Lorito,2 and Enrique Monte1

1Centro Hispano-Luso de Investigaciones Agrarias (CIALE). Departamento de Microbiología y Genética, Universidad de Salamanca, Campus de Villamayor, C/ Duero 12. 37185 Salamanca, Spain; 2Dipartamento di Arboricoltura, Botanica e Patologia Vegetale, Università degli Studi di Napoli Federico II, Via Università 100, 80055 Portici (NA), Italy; 3área de Microbiología, Escuela Universitaria de Ciencias de la Salud. Universidad de León, Campus de Ponferrada, Avda. Astorga s/n. 24400 Ponferrada, Spain

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Accepted 14 April 2009.

Considering the complexity of the in vivo interactions established by a mycoparasitic biocontrol agent at the plant rhizosphere, proteomic, genomic, and transcriptomic approaches were used to study a novel Trichoderma gene coding for a plant cell wall (PCW)-degrading enzyme. A proteome analysis, using a three-component (Trichoderma spp.--tomato plantlets--pathogen) system, allowed us to identify a differentially expressed Trichoderma harzianum endopolygalacturonase (endoPG). Spot 0303 remarkably increased only in the presence of the soilborne pathogens Rhizoctonia solani and Pythium ultimum, and corresponded to an expressed sequence tag from a T. harzianum T34 cDNA library that was constructed in the presence of PCW polymers and used to isolate the Thpg1 gene. Compared with the wild-type strain, Thpg1-silenced transformants showed lower PG activity, less growth on pectin medium, and reduced capability to colonize tomato roots. These results were combined with microarray comparative data from the transcriptome of Arabidopsis plants inoculated with the wild type or a Thpg1-silenced transformant (ePG5). The endoPG-encoding gene was found to be required for active root colonization and plant defense induction by T. harzianum T34. In vivo assays showed that Botrytis cinerea leaf necrotic lesions were slightly smaller in plants colonized by ePG5, although no statistically significant differences were observed.

© 2009 The American Phytopathological Society