Project description:Transcript-Level Variation in Barley Seedling Leaves Challenged with Puccinia hordei and the Molecular Basis of Partial Resistance to Leaf Rust
Project description:Transcript-Level Variation in Barley Seedling Leaves Challenged with Puccinia hordei and the Molecular Basis of Partial Resistance to Leaf Rust
Project description:Time course: Interaction of Puccinia hordei with Hordeum vulgare, Ingrid (leaf) and Puccinia triticana with Hordeum vulgare, Ingrid (leaf)
Project description:In this experiment the transcriptome reprogramming in wheat during host and nonhost interaction with Puccinia sp. was analyzed in a time-series approach. Ten days old wheat plants of cv. Renan were mock-inoculated or inoculated with P. triticina (Pt), BRW96258 isolate, or P. hordei (Ph), 1.2.1 isolate. After 12, 24, 36 and 48 hours first leaves were sampled. Total RNA was extracted using the RNeasy Plant Mini Kit (Qiagen, Hilden, Germany), the Ambion TURBO DNA-free DNase Kit was used for DNA elimination, and RNA was hybridized to Agilent 44k oligonucleotide arrays.
Project description:In this experiment the transcriptome reprogramming in barley during host and nonhost interaction with Puccinia sp. was analyzed in a time-series approach. Ten days old barley plants of cv. Vada were mock-inoculated or inoculated with P. hordei (Ph), 1.2.1 isolate, or P. triticina (Pt), BRW96258 isolate. After 12, 24, 36 and 48 hours first leaves were sampled. Total RNA was extracted using the RNeasy Plant Mini Kit (Qiagen, Hilden, Germany), the Ambion TURBO DNA-free DNase Kit was used for DNA elimination, and RNA was hybridized to Agilent 44k oligonucleotide arrays.
Project description:BACKGROUND: The barley-Puccinia hordei (barley leaf rust) pathosystem is a model for investigating partial disease resistance in crop plants and genetic mapping of phenotypic resistance has identified several quantitative trait loci (QTL) for partial resistance. Reciprocal QTL-specific near-isogenic lines (QTL-NILs) have been developed that combine two QTL, Rphq2 and Rphq3, the largest effects detected in a recombinant-inbred-line (RIL) population derived from a cross between the super-susceptible line L94 and partially-resistant line Vada. The molecular mechanism underpinning partial resistance in these QTL-NILs is unknown. RESULTS: An Agilent custom microarray consisting of 15,000 probes derived from barley consensus EST sequences was used to investigate genome-wide and QTL-specific differential expression of genes 18 hours post-inoculation (hpi) with Puccinia hordei. A total of 1,410 genes were identified as being significantly differentially expressed across the genome, of which 55 were accounted for by the genetic differences defined by QTL-NILs at Rphq2 and Rphq3. These genes were predominantly located at the QTL regions and are, therefore, positional candidates. One gene, encoding the transcriptional repressor Ethylene-Responsive Element Binding Factor 4 (HvERF4) was located outside the QTL at 71 cM on chromosome 1H, within a previously detected eQTL hotspot for defence response. The results indicate that Rphq2 or Rphq3 contains a trans-eQTL that modulates expression of HvERF4. We speculate that HvERF4 functions as an intermediate that conveys the response signal from a gene(s) contained within Rphq2 or Rphq3 to a host of down-stream defense responsive genes. Our results also reveal that barley lines with extreme or intermediate partial resistance phenotypes exhibit a profound similarity in their spectrum of Ph-responsive genes and that hormone-related signalling pathways are actively involved in response to Puccinia hordei. CONCLUSIONS: Differential gene expression between QTL-NILs identifies genes predominantly located within the target region(s) providing both transcriptional and positional candidate genes for the QTL. Genetically mapping the differentially expressed genes relative to the QTL has the potential to discover trans-eQTL mediated regulatory relays initiated from genes within the QTL regions.
Project description:The biotrophic rust fungi Puccinia hordei and Puccinia striiformis are important barley pathogens with the potential to cause high yield losses through an epidemic spread. The identification of QTL conferring resistance to these pathogens is the basis for targeted breeding approaches aiming to improve stripe rust and leaf rust resistance of modern cultivars. Exploiting the allelic richness of wild barley accessions proved to be a valuable tool to broaden the genetic base of resistance of barley cultivars. In this study, SNP-based nested association mapping (NAM) was performed to map stripe rust and leaf rust resistance QTL in the barley NAM population HEB-25, comprising 1,420 lines derived from BC1S3 generation. By scoring the percentage of infected leaf area, followed by calculation of the area under the disease progress curve and the average ordinate during a two-year field trial, a large variability of resistance across and within HEB-25 families was observed. NAM based on 5,715 informative SNPs resulted in the identification of twelve and eleven robust QTL for resistance against stripe rust and leaf rust, respectively. Out of these, eight QTL for stripe rust and two QTL for leaf rust are considered novel showing no overlap with previously reported resistance QTL. Overall, resistance to both pathogens in HEB-25 is most likely due to the accumulation of numerous small effect loci. In addition, the NAM results indicate that the 25 wild donor QTL alleles present in HEB-25 strongly differ in regard to their individual effect on rust resistance. In future, the NAM concept will allow to select and combine individual wild barley alleles from different HEB parents to increase rust resistance in barley. The HEB-25 results will support to unravel the genetic basis of rust resistance in barley, and to improve resistance against stripe rust and leaf rust of modern barley cultivars.