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PLANTS INTERACTING WITH OTHER ORGANISMS

Transgenic Expression of a Fungal endo-Polygalacturonase Increases Plant Resistance to Pathogens and Reduces Auxin Sensitivity^1,[W]

Dipartimento di Biologia Vegetale, Università degli Studi di Roma La Sapienza, 00185 Rome, Italy

Polygalacturonases (PGs), enzymes that hydrolyze the homogalacturonan of the plant cell wall, are virulence factors of several phytopathogenic fungi and bacteria. On the other hand, PGs may activate defense responses by releasing oligogalacturonides (OGs) perceived by the plant cell as host-associated molecular patterns. Tobacco (Nicotiana tabacum) and Arabidopsis (Arabidopsis thaliana) plants expressing a fungal PG (PG plants) have a reduced content of homogalacturonan. Here, we show that PG plants are more resistant to microbial pathogens and have constitutively activated defense responses. Interestingly, either in tobacco PG or wild-type plants treated with OGs, resistance to fungal infection is suppressed by exogenous auxin, whereas sensitivity to auxin of PG plants is reduced in different bioassays. The altered plant defense responses and auxin sensitivity in PG plants may reflect an increased accumulation of OGs and subsequent antagonism of auxin action. Alternatively, it may be a consequence of perturbations of cellular physiology and elevated defense status as a result of altered cell wall architecture.

² These authors contributed equally to the article.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Giulia De Lorenzo (giulia.delorenzo{at}uniroma1.it).

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.107.109686

^* Corresponding author; e-mail giulia.delorenzo{at}uniroma1.it.

Received September 24, 2007; accepted November 28, 2007; published December 7, 2007.