Genome-Wide Expression Profiling Arabidopsis at the Stage ofGolovinomyces cichoracearumHaustorium Formation    

Abstract

(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 Powdery Mildew Disease of Arabidopsis: A Paradigm for the Interaction between Plants and Biotrophic Fungi

“…interaction between Arabidopsis and G. cichoracearum, revealed that host photosynthesis is likely stimulated by the fungus, through the induction of genes involved in chlorophyll binding and chlorophyll a oxygenase (Fabro et al, 2008). Though it is conceivable that an increase in photosynthetic rate is required, as the metabolic demands of the infected epidermal tissue increase, these findings are somewhat contradictory to those obtained in the study of Zimmerli et al (2004).…”

“…The broad range of transcriptional changes that occur in Arabidopsis during powdery mildew infection , Fabro et al, 2008 reflect both defense responses mounted by the plant as well as possible manipulation of the host by the fun-gal pathogen. With the sequencing of the Arabidopsis genome and availability of novel technologies for transcript profiling (oligonucleotide-based microarray chips) it has been possible to peek into the gene expression changes that occur during the infection process.…”

Patterns of Population Structure and Environmental Associations to Aridity Across the Range of Loblolly Pine (Pinus taedaL., Pinaceae)

“…The primary functions of gene products encoded by these loci were abiotic and biotic stress responses. All five loci have putative orthologs in Arabidopsis that are responsive to abscisic (ABA) or jasmonic (JA) acid, two plant hormones with well-documented correlations to abiotic stress responses (Glazebrook et al 2003;Wong et al 2006;Wasternack 2007;Fabro et al 2008;Mizuno and Yamashino 2008). In addition, gene expression for four of the five loci in f P-values listed in boldface type are also significant using a Bonferroni correction.…”

Laser microdissection of Arabidopsis cells at the powdery mildew infection site reveals site-specific processes and regulators

“…TFs often exhibit low-level and highly localized expression changes; therefore, we expected our site-specific expression analysis to identify unique TFs with important functional roles in the PM interaction. We found 67 TFs exhibited altered expression at the site of infection, with 79% not previously associated with a compatible PM interaction (4,(7)(8)(9). Although many of these PM site-specific TFs have no defined function, we identified sets of TFs associated with the following processes: photosynthesis, drought/cold tolerance, pathogen defense and cell death, auxin signaling/response, and the cell cycle (Fig.…”