Towards an understanding of the molecular mechanisms of durable and non-durable resistance to stripe rust
Towards an understanding of the molecular mechanisms of durable and non-durable resistance to stripe rust Xianming ChenUSDA-ARS, Wheat Genetics, Quality, Physiology, and Disease Research Unit, Pullman, WA andDepartment of Plant Pathology, Washington State University
Stripe rust damage can be HUGE Average 2010 3 860 10 20 30 40 50 60 70 80 90 100
Distribution of Stripe Rust in the US in 2010Grain Yield Loss in the US2003: 89 M. Bu (2.42 M. MT)2005: 73 M. Bu (1.99 M. MT)2010: 87 M. Bu (2.38 M. MT)
In Washington State in 2010:•The various levels of resistance including HTAPresistance were estimated to reduce yield loss frompotentially more than 60% to about 9%.• The application of fungicides in more than 60% of winterand spring wheat acreage in Washington State wasestimated to reduce yield loss further to about 3% (about4.5 million bushels) in average.• The total resistance in all wheat cultivars collectively wasable to save 73 million bushes ($512 million) and thefungicide application further saved 13.7 million bushels($96 million) at the cost of estimated over $27 million.
All-Stage (Seedling) Resistance:Can be detected in seedling stageEffective in all growth stages Yr5 AVSHigh-level resistanceEasy to incorporate into cultivarsNot durable if a single gene is involved
Dr. Orville A. Vogel was the first to develop wheat cultivars with partial resistance to stripe rust IT and % in 2008 Pullman Mt. Vernon Cultivar Release Flow. S. elong Head. Brevor 1949 3 30 5 30 2 20 Omar 1955 8 90 8 60 8 100 Gaines 1960 5 50 8 60 5 60 Nugaines 1965 5 40 8 40 3 40 Luke 1970 2 10 3 15 3 5Photo source: http://cahnrsnews.wsu.edu/reportertools/news/2007/vogel-building-2007-09.html
Dr. Roland F. Linecharacterized high-temperatureadult-plant (HTAP) resistance asthe type of resistance expressedat high post-inoculationtemperatures and at adult-plantstage.
High-Temperature Adult-Plant Resistance Expresses when weather is warm and plants grow old Low to high-level resistance Durable Conferred by quantitative trait loci Relatively difficult to detect and difficult to incorporate into cultivars May not be adequate
Why is race-specific all-stage resistancenot durable and nonrace-specific HTAP resistance durable?
Wheat GeneChip 55,052 probe sets Derived from the public content of the T. aestivum UniGene Build #38 Probe sets consist of pairs of 11 perfect match (PM) and mismatch (MM) 25-mer oligonucleotides
Yr5 Experimental Design Near isogenic lines (Isolines) Yr5 AvS Yr5 (AvSYr5NIL: resistant) yr5 (AvS: susceptible) Mock- and P. s. tritici-inoculation Seedling stage (~10 days) PST-100 Time-course sampling (6, 12, 24, 48 h) 3 biological replicates RNA extraction, labeling and hybridization
Differential Expression In reference to mock-inoculated controls For Yr39 HTAP resistance interaction 215 transcripts significant at 48 hpi 207 induced and 8 repressed For yr39 compatible interaction Just 1 transcript induced at 48 hpi
HTAP Resistance-Specific Transcripts• All 99 transcripts were induced• 50.5% involved in pathogen defense and signal transduction• 10 R gene-like transcripts including; – Yr10 all-stage stripe rust resistance protein – Cf2/Cf5 disease resistance protein homolog – Barley stem rust resistance protein Rpg1 – Maize NADPH-dependent HC-toxin reductase Hm1 homolog
HTAP Resistance-Specific Transcripts• Other interesting induced transcripts; – Several protein kinase signaling proteins – Transcriptional regulatory transcripts including a WRKY5 homolog – Five beta-1,3-glucanase transcripts – Wheat pathogen-induced WIR1A protein – Six phenylalanine ammonia-lyase (PAL) transcripts• Quantitative RT-PCR confirmed results
Genes Regulated by Yr5 Race-Specific and Yr39 Nonrace-Specific Resistance to Stripe RustRace-specific Basal Nonrace-specific Basalresistance defense resistance defense yr39 Yr5 yr5 Yr39 61 19 99 1HR 54specific Biotrophic 91 interaction specific
Comparison of transcripts regulated by the Yr5 race-specific all-stage resistance and the Yr39 nonrace-specific HTAP resistanceRace-specific Nonrace-specific resistance resistance Yr5 Yr39 61 99 14
Meta-analysis Design• Custom oligonucleotide microarray – 116 significant transcripts from Yr5 results – 207 significant transcripts from Yr39 results• Aim to identify common/unique gene expression signatures involved in each resistance
Resistance Type Comparison (More Genes of Races-Specific vs. Nonrace-specific)• 8 wheat genotypes with race-specific resistance – Yr1, Yr5, Yr7, Yr8, Yr9, Yr10, Yr15 and Yr17• 4 genotypes with nonrace-specific resistance – Yr18, Yr29, Yr36 and Yr39• Mock and incompatible interaction – Seedling and adult plant stage
Race-specific Resistance• Seedling stage phenotype effect – Combined genotype data• 28 transcripts significant – P <0.10 and fold change >2.0• Compared to 116 transcripts in Yr5 response – Meta-analysis narrowed the gene list
Transcript AnnotationFunctional category Putative function Fold change p valueDefense Putative disease resistance protein 2.45 0.017Defense Putative disease resistance protein 2.36 0.017Defense - alkaloid 28 transcripts annotated • 21 of the Reticuline oxidase 2.01 0.078Defense - cell wall Pathogen induced WIR1A protein 2.15 0.000 – 15 (71%) involved in defense/signalingDefense - oxidative stress Blue copper-binding protein 4.11 0.000Defense - oxidative stress Blue copper-binding protein 2.35 0.012Defense - oxidative stress Peroxidase 2.54 0.022Defense - oxidative stress Peroxidase 2.71 0.089Defense - phenylpropanoid Phenylalanine ammonia-lyase 2.13 0.004Defense - phenylpropanoid Phenylalanine ammonia-lyase 5.43 0.001Defense - PR protein Beta-1,3-glucanase 2.04 0.087Defense - PR protein PR protein 10 2.01 0.003Defense - R protein NB-ARC domain containing protein 2.66 0.024Signal transduction Calmodulin-binding protein 2.82 0.055Signal transduction LRR-containing extracellular glycoprotein 2.57 0.001Transcription Transcription factor 2.40 0.000
Nonrace-specific resistance• Only detectable at adult-stage• Zero significant transcripts for nonrace- specific resistance phenotype effect• Directly compared race-specific resistance to nonrace-specific resistance – 5 transcripts significant for race-specific resistance – 1 transcript significant for nonrace-specific resistance
Race-specific resistanceFunctional Category Putative Function Fold change p valueDefense - cell wall Hydroxyproline-rich glycoprotein 10.78 0.000Defense - R protein NB-ARC domain containing protein 2.22 0.006Signal transduction Protein kinase 5.50 0.000Unknown No homology 4.38 0.000Unknown No homology 2.43 0.000 Nonrace-specific resistanceFunctional category Putative function Fold change p valueTransport Nonclathrin coat protein 2.16 0.000
Relationships of Yr genes based on common and unique transcripts in response to stripe rust infection Yr1 Yr5 Yr17 Yr15 Yr8 Yr10 Yr18 Yr39 Yr9 Yr29
Conclusions and Perspectives In comparison with race-specific all-stage resistance, nonrace- specific HTAP resistance is contributed by a relatively great number of defense-related genes, which may explain the durability of HTAP resistance. Genes contributing to all-stage resistance are induced fast and their transcription levels increased dramatically in the infection process, while those contributing to HTAP resistance are induced more slowly and their transcription changes are less dramatic. All-stage resistances mediated by different R genes tend to share many common defense genes, while HTAP resistances-mediated by different genes do not have many defense genes in common. Transcription factors identified in these studies may play key roles in the networks of plant defense. Further characterization of these genes may enhance our understanding of molecular mechanisms of different types of resistance.
Genes with similar sequence to Ta.6990.1.S1 Ta.6990.1.S1_at is likely a PDR [Pleiotropic Drug Resistance]-type ABC [ATP Binding Cassette] transporter
ABC Geneassociated withTa.6990.1.S1_at Yr18/Lr34 Ta.6990.1.S1_at Yr18/Lr34 Size (kb) 7.4 11.8 Introns 18 24 Chromosome 7A* 7D*• Lr34-A, a homolog of Lr34, is located on 7A, but its sequence is dissimilar from the Ta.6990.1 associated gene.The gene associated with the Ta.6990.1.S1 transcript issubstantially different from Yr18/Lr34 (47% similar) eventhough both are PDR- type ABC transporters.
Thank You Tristan Coram Xueling Huang Meinan Wang Andrea Dolezal