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PLANTS INTERACTING WITH OTHER ORGANISMS

Genome-Wide Expression Profiling Arabidopsis at the Stage of Golovinomyces cichoracearum Haustorium Formation^1,[W],[OA]

CIQUIBIC-CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas (G.F., M.E.A.) and Cátedra de Estadística y Biometría, Facultad de Ciencias Agropecuarias (J.A.D.R.), Universidad Nacional de Córdoba, 5000 Córdoba, Argentina; Carnegie Institution, Department of Plant Biology, Stanford, California 94305 (C.A.V., S.S.); and Section of Plant Biology, University of California, Davis, California 95616 (T.S., K.D.)

Compatibility between plants and obligate biotrophic fungi requires fungal mechanisms for efficiently obtaining nutrients and counteracting plant defenses under conditions that are expected to induce changes in the host transcriptome. A key step in the proliferation of biotrophic fungi is haustorium differentiation. Here we analyzed global gene expression patterns in Arabidopsis thaliana leaves during the formation of haustoria by Golovinomyces cichoracearum. At this time, the endogenous levels of salicylic acid (SA) and jasmonic acid (JA) were found to be enhanced. The responses of wild-type, npr1-1, and jar1-1 plants were used to categorize the sensitivity of gene expression changes to NPR1 and JAR1, which are components of the SA and JA signaling pathways, respectively. We found that the infection process was the major source of variation, with 70 genes identified as having similarly altered expression patterns regardless of plant genotype. In addition, principal component analysis (PCA) identified genes responding both to infection and to lack of functional JAR1 (17 genes) or NPR1 (18 genes), indicating that the JA and SA signaling pathways function as secondary sources of variation. Participation of these genes in the SA or JA pathways had not been described previously. We found that some of these genes may be sensitive to the balance between the SA and JA pathways, representing novel markers for the elucidation of cross-talk points between these signaling cascades. Conserved putative regulatory motifs were found in the promoter regions of each subset of genes. Collectively, our results indicate that gene expression changes in response to infection by obligate biotrophic fungi may support fungal nutrition by promoting alterations in host metabolism. In addition, these studies provide novel markers for the characterization of defense pathways and susceptibility features under this infection condition.

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: María Elena Alvarez (malena{at}mail.fcq.unc.edu.ar).

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

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www.plantphysiol.org/cgi/doi/10.1104/pp.107.111286

^* Corresponding author; e-mail malena{at}mail.fcq.unc.edu.ar.

Received October 19, 2007; accepted January 8, 2008; published January 24, 2008.