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Microarray analysis of med16, med8, elp2, and wild type (Col-0) infected with the necrotrophic fungal pathogen Sclerotinia sclerotiorum

ABSTRACT: The goal of the microarray experiment was to identify defense genes that were differentially expressed in the Arabidopsis mutants med16, med8, elp2, wild type in response to infection of the necrotrophic fungal pathogen Sclerotinia sclerotiorum. Results indicated that, compared with the wild type, the jasmonic acid (JA) biosynthesis genes LOX3, AOC3, and OPR3, ethylene (ET) biosynthesis genes ACS2 and ACS8, as well as salicylic acid (SA) biosynthesis genes ICS1 and EDS5 were up-regulated in med16 in local tissues at 1 day post-inoculation (dpi) and/or systemic tissues at 4 dpi. Surprisingly, however, while a number of SA pathway genes (EDS1, PAD4, NPR1, WRKY18, WRKY38, WRKY53, PR1, and PR2) and several JA-regulated wound-responsive genes (MYC2, JAR1, VSP1, and VSP2) were up-regulated in med16, a group of JA/ET-regulated defense genes (ORA59, ERF1, ERF14, PDF1.2, PDF1.2b, PDF1.2c, PDF1.3, PR4, and ChiB) and PR5 were down-regulated. On the other hand, only a few of these genes were differentially expressed between med8 or elp2 and the wild type.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE65165 | GEO | 2015/01/22

SECONDARY ACCESSION(S): PRJNA273319

REPOSITORIES: GEO

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Project description:Phytophthora cinnamomi Rands (Pc) is a hemibiotrophic oomycete and the causal agent of Phytophthora root rot (PRR) of the commercially important fruit crop avocado (Persea americana Mill.). Plant defense against pathogens is modulated by phytohormone signaling pathways such as salicylic acid (SA), jasmonic acid (JA), ethylene (ET), auxin and abscisic acid. The role of specific signaling pathways induced and regulated during hemibiotroph-plant interactions has been widely debated. Some studies report SA mediated defense while others hypothesize that JA responses restrict the spread of pathogens. This study aimed to identify the role of SA- and JA- associated genes in the defense strategy of a resistant avocado rootstock, Dusa® in response to Pc infection. Transcripts associated with SA-mediated defense pathways and lignin biosynthesis were upregulated at 6 hours post-inoculation (hpi). Results suggest that auxin, reactive oxygen species (ROS) and Ca2+ signaling was also important during this early time point, while JA signaling was absent. Both SA and JA defense responses were shown to play a role during defense at 18 hpi. Induction of genes associated with ROS detoxification and cell wall digestion (β-1-3-glucanase) was also observed. Most genes induced at 24 hpi were linked to JA responses. Other processes at play in avocado at 24 hpi include cell wall strengthening, the formation of phenolics and induction of arabinogalactan, a gene linked to Pc zoospore immobility. This study represents the first transcriptome wide analysis of a resistant avocado rootstock treated with SA and JA compared to Pc infection. The results provide evidence of a biphasic defense response against the hemibiotroph, which initially involves SA-mediated gene expression followed by the enrichment of JA-mediated defense from 18 to 24 hpi. Genes and molecular pathways linked to Pc resistance are highlighted and may serve as future targets for manipulation in the development of PRR resistant avocado rootstocks.

Project description:Salicylic acid (SA) is a critical molecule mediating plant innate immunity with an important role limiting the growth and reproduction of the virulent powdery mildew (PM) Golovinomyces orontii on Arabidopsis thaliana. To investigate this later phase of the PM interaction, and the role played by SA, we performed replicated global expression profiling for wild type and SA biosynthetic mutant ics1 Arabidopsis from 0 to 7 days post infection. We found that ICS1-impacted genes comprise 3.8% of profiled genes with known molecular markers of Arabidopsis defense ranked very highly by the multivariate empirical Bayes statistic (T2 statistic ((Tai and Speed, 2006)). Functional analyses of T2-selected genes identified statistically significant PM-impacted processes including photosynthesis, cell wall modification, and alkaloid metabolism that are ICS1-independent. ICS1-impacted processes include redox, vacuolar transport/secretion, and signaling. Our data also supports a role for ICS1 (SA) in iron and calcium homeostasis and identifies components of SA crosstalk with other phytohormones. Through our analysis, 39 novel PMâimpacted transcriptional regulators were identified. Insertion mutants in one of these regulators, PUX2, results in significantly reduced reproduction of the powdery mildew in a cell death independent manner. Though little is known about PUX2, PUX1 acts as a negative regulator of Arabidopsis CDC48 (Rancour et al., 2004; Park et al., 2007), an essential AAA-ATPase chaperone that mediates diverse cellular activities including homotypic fusion of ER and Golgi membranes, ER-associated protein degradation, cell cycle progression, and apoptosis. Future work will elucidate the functional role of the novel regulator PUX2 in PM resistance. Experiment Overall Design: Arabidopsis whole leaves were harvested at 6h, 1 day, 3 days, 5 days and 7 days after Golovinomyces orontii infection for RNA extraction and hybridization to Affymetrix Arabidopsis ATH1 microarrays. Gene expression profiles were obtained for wild type Columbia-0 and enhanced disease susceptibility mutant eds16-1, a null isochorismate synthase 1 (At1g74710) mutant. In parallel, uninfected samples were collected at 0 hr and 7days from wild type and mutant plants. The experiment includes 4 biological replicates.

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Microarray analysis of med16, med8, elp2, and wild type (Col-0) infected with the necrotrophic fungal pathogen Sclerotinia sclerotiorum

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