Impact of dormancy genotypes on differential protein expression profiles and redox-sensitive proteome in seeds of hybrid spring wheat lines

Hu, Junjie Grace (2011) Impact of dormancy genotypes on differential protein expression profiles and redox-sensitive proteome in seeds of hybrid spring wheat lines. Masters thesis, Memorial University of Newfoundland.

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Abstract

Seed survival in the soil and cycling through states of dormancy is a key component determining entry and persistence in ecosystems, and seed dormancy is a major trait altered during domestication of wild species. The potential for dormancy is overcome through the time- and environment-sensitive process of after-ripening that occurs in the dry seed. The dormant condition is not a quiescent state; it is a dynamic state in which cell metabolism is active, although growth is repressed. Dormancy is thought to be under the control of two distinct processes: the accumulation of damaging Reactive Oxygen Species (ROS), a critical level of which leads to dormancy alleviation, and a hormonal balance that regulates dormancy directly and likely interacts with ROS and/or antioxidative pathways. The precise mechanisms by which ORS affect seed dormancy status and germination potential remain to be elucidated. Thiol-disulfide proteins are particularly important for redox-dependent regulation of metabolic and developmental activities in cells as functional ‘hotspots’ in the proteome. Differential proteomic analysis of six hybrid lines of spring wheat (Triticum aestivum L.) doubled haploid population, derived from the cross 8021-V2 (high dormancy) x AC Karma (low dormancy) segregating transgressively for dormancy phenotype, and two parent genotypes, was addressed to gain further insight into biochemical mechanisms underlying dormancy controlling events. The thiol redox-sensitive and the total proteome were quantitatively monitored by 2D-gel electrophoresis combined with solubility-based protein fractionation, fluorescent thiol-specific labelling, and mass spectrometry analysis in conjunction with wheat EST sequence libraries. -- Quantitative differences between genotypes were found for 106 spots containing 65 unique proteins. Forty-seven unique proteins displayed distinctive abundance pattern, and of these 31 proteins contained 78 unique redox active cysteines Seventeen unique proteins with 19 reactive modified cysteines were found to have differential post-translational thiol redox modification. The results give an insight into the dormancy-related alteration of thiol-redox profiles in seed proteins that function in a number of major processes in seed physiology. In dormant seeds, there is a shift in the accumulation of proteins from those active in biosynthesis and metabolism to those with roles in storage and protection against biotic and abiotic stresses. The proteomic data provide evidence for an increased capacity of potent antioxidant machinery in seeds of high non-deep physiological dormancy wheat genotypes, which could be coupled with their ability to regenerate antioxidant systems rapidly upon rehydration for dormancy maintenance.

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