Temporal Gene Expression Profiling of the Wheat Leaf Rust Pathosystem Using cDNA Microarray Reveals Differences in Compatible and Incompatible Defence Pathways

Abstract

In this study, we detail the construction of a custom cDNA spotted microarray containing 7728 wheat ESTs and the use of the array to identify host genes that are differentially expressed upon challenges with leaf rust fungal pathogens. Wheat cultivar RL6003 (Thatcher Lr1) was inoculated with Puccinia triticina virulence phenotypes BBB (incompatible) or TJB (7-2) (compatible) and sampled at four different time points (3, 6, 12, and 24 hours) after inoculation. Transcript expression levels relative to a mock treatment were measured. One hundred ninety two genes were found to have significantly altered expression between the compatible and incompatible reactions. Among those were genes involved in photosynthesis, the production of reactive oxygen species, ubiquitination, signal transduction, as well as in the shikimate/phenylpropanoid pathway. These data indicate that various metabolic pathways are affected, some of which might be used by RL6003 to mount a coordinated defense against an incompatible fungal pathogen.

An Overview of Plant Photosynthesis Modulation by Pathogen Attacks

“…Pathogen attacks result in the development of symptoms that include leaf and fruit wilt, stem and root rot (Rekah et al, 1999), coverage of leaf surface with pustule, chlorosis and necrosis (Fofana et al, 2007, Kocal et al, 2008 (Figure 2), a decreased rate of plant photosynthesis (Kocal et al, 2008), and as a consequence plant death or yield loss ensues (Berger et al, 2007). Fig.…”

“…Photosynthesis was significantly reduced within 12 h of toxin treatment, prior to the development of chlorosis at 48-72 h. Proteomics analysis by 2-DE revealed a total of 102 protein spots with significantly altered intensities 12-36 h after toxin treatment, of which 66 were more abundant and 36 were less abundant than in the buffer-treated control. In the last decade, an abundant literature has treated large dataset gene expression profiling of plant-pathogen interactions (Bilgin et al, 2010, Eichmann et al, 2006, Fofana et al, 2007, Lee et al, 2004, Zou et al, 2005) among many others. Of interest was the study by Fofana et al (Fofana et al, 2007) where difference in temporal gene expression profiling of the wheat leaf rust pathosystem was reported in compatible and incompatible defence pathways using cDNA microarray.…”

“…In the last decade, an abundant literature has treated large dataset gene expression profiling of plant-pathogen interactions (Bilgin et al, 2010, Eichmann et al, 2006, Fofana et al, 2007, Lee et al, 2004, Zou et al, 2005) among many others. Of interest was the study by Fofana et al (Fofana et al, 2007) where difference in temporal gene expression profiling of the wheat leaf rust pathosystem was reported in compatible and incompatible defence pathways using cDNA microarray. Gene ontology assignment of differentially expressed genes showed alterations in gene expression for different molecular functions, cellular location and biological process for genes (Figure 3).…”

“…Gene ontology assignment of differentially expressed genes showed alterations in gene expression for different molecular functions, cellular location and biological process for genes (Figure 3). The authors observed changes in the expression of genes involved in different biological processes such as photosynthesis, redox control, resistance and resistance-related genes (NBS-LRR, cyclophilin-like protein, MLo4-like gene, MRP1), components of the shikimatephenylpropanoid pathway as well as genes involved in signal transduction (Myb-like transcription factors, calmodulin MAPKK, PI4PK), heat shock proteins, osmotic control genes and metabolisms (Fofana et al, 2007). Six hours after inoculation, a coordinated decrease in transcription of photosynthesis genes (photosystemmII phosphoprotein, ribulose-1,5 biphosphate carboxylase/oxygenase small unit, Type III LHCII CAB precursor protein, photosystem II type II chlorophyll A/B-binding protein, ribulose-1,5 biphosphate carboxylase activase) in the resistant but not susceptible interactions was observed in agreement with the general trends of photosynthesis inhibition.…”

“…3. Gene ontology assignment of differentially expressed genes (Fofana et al, 2007). A BLASTX search of the differentially expressed sequences against the set of predicted Arabidopsis thaliana proteins was used to assign gene ontology.…”