Integrated proteogenomics approach to reveal sources of pre- harvest sprouting resistance in Canadian wheat.

The integration of multiple measurements in proteogenomics provides a powerful approach to capture functional modules that discriminate between the sources for pre-harvest sprouting resistance or susceptibility. We analyzed dormancy-imposing processes in embryo and aleurone tissue-specific proteomes and redox metabolomes using spring wheat (Triticum aestivum L.) doubled haploid hybrid lines with marginal dormancy phenotypes, comparative iTRAQ-based protein quantitation, fluorescent labeling and 2DE-based thiol redox proteomics, and redox metabolite measurements. iTRAQ-based approach resulted in over 6800 high confidence protein identifications, of which 62 and 115 unique proteins showed significant differential expression in dormant phenotypes, and 368 and 1041 unique proteins were dormancy genotype-specific in embryo and aleurone, respectively. In dormant embryos, significant alterations were found for protein translation, folding, transport and degradation, DNA-repair, and mRNA surveillance, oxidative and nitrosative stress response. Potentially critical for imposing dormancy and after-ripening regulation, changes were found in cell cycle control, epigenetic regulation of gene expression, arrest of development and growth. Proteins responsible for natural defences against pathogens were up-regulated in dormant aleurone. Corresponding genes on chromosome arms where QTL for sprouting tolerance had been previously identified were further analysed to compare their location in the QTL region. The level of total glutathione was significantly higher in dormant embryo tissues, and the capacity for GSSG disulfide regeneration decreased dramatically upon after-ripening. In dormant embryos, the concentration of total and reduced ascorbate increased 2-3 fold during after-ripening indicating high capacity for ascorbate regeneration, which reveals different roles of ascorbate and glutathione in redox control of dormancy.