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The Arabidopsis AtNPR1 Inversely Modulates Defense Responses Against Fungal, Bacterial, or Viral Pathogens While Conferring Hypersensitivity to Abiotic Stresses in Transgenic Rice

September 2008 , Volume 21 , Number  9
Pages  1,215 - 1,231

Jordi Quilis,1,2 Gisela Peñas,1,3 Joaquima Messeguer,3 Christophe Brugidou,4 and Blanca San Segundo1,2

1Consorcio CSIC-IRTA Laboratorio de Genética Molecular Vegetal, Jordi Girona 18, 08034 Barcelona, Spain; 2Departamento de Genética Molecular, 3Departamento de Genética Vegetal, and 4Institut de Recherche pour le Développement, UMR 5096 (CNRS-IRD-UP), Montpellier, France

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Accepted 27 April 2008.

The nonexpressor of pathogenesis-related (PR) genes (NPR1) protein plays an important role in mediating defense responses activated by pathogens in Arabidopsis. In rice, a disease-resistance pathway similar to the Arabidopsis NPR1-mediated signaling pathway one has been described. Here, we show that constitutive expression of the Arabidopsis NPR1 (AtNPR1) gene in rice confers resistance against fungal and bacterial pathogens. AtNPR1 exerts its protective effects against fungal pathogens by priming the expression of salicylic acid (SA)-responsive endogenous genes, such as the PR1b, TLP (PR5), PR10, and PBZ1. However, expression of AtNPR1 in rice has negative effects on viral infections. The AtNPR1-expressing rice plants showed a higher susceptibility to infection by the Rice yellow mottle virus (RYMV) which correlated well with a misregulation of RYMV-responsive genes, including expression of the SA-regulated RNA-dependent RNA polymerase 1 gene (OsRDR1). Moreover, AtNPR1 negatively regulates the expression of genes playing a role in the plant response to salt and drought stress (rab21, salT, and dip1), which results in a higher sensitivity of AtNPR1 rice to the two types of abiotic stress. These observations suggest that AtNPR1 has both positive and negative regulatory roles in mediating defense responses against biotic and abiotic stresses.

Additional keywords:Erwinia chrysanthemi, Fusarium verticillioides, Magnaporthe oryzae, and Oryza sativa.

© 2008 The American Phytopathological Society