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Functional Characterization of a Gene Family Encoding Polygalacturonases in Phytophthora parasitica

April 2008 , Volume 21 , Number  4
Pages  480 - 489

Chih-Hang Wu,1 Hao-Zhi Yan,1 Li-Fei Liu,2 and Ruey-Fen Liou1,3

1Department of Plant Pathology and Microbiology, 2Department of Agronomy, and 3Institute of Biotechnology, National Taiwan University, Taipei 106, Taiwan

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Accepted 10 December 2007.

Phytophthora parasitica is an oomycete plant pathogen that causes severe disease in a wide variety of plant species. In our previous study, we discovered a multigene family encoding endopolygalacturonases (endoPG) in Phytophthora parasitica. Here, we screened the genomic library of Phytophthora parasitica for the genes encoding endoPG named pppg2 through pppg10, and analyzed their functions. Results obtained by real-time quantitative reverse transcriptase-polymerase chain reaction demonstrated that some of these genes are highly induced during plant infection, which suggests their important roles in the pathogenesis of Phytophthora parasitica. Analysis by in-gel activity assay of recombinant proteins obtained from Pichia pastoris indicated that each of these genes encodes a functional endoPG. Investigation of the function of pppg genes in planta by a Potato virus X agroinfection system in tobacco revealed that each pppg caused specific effects, varying from no symptoms to dwarfism, necrosis, leaf curl, silvery leaf, and cracks in leaf stalks. Appearance of these effects depends on the expression of a pppg protein with a normal active site in the apoplast. These results indicated that each pppg plays a distinct role in the decomposition of plant cell wall.

© 2008 The American Phytopathological Society