Heat-shock proteins in monitoring aging and heat-induced tolerance in germinating wheat and barley embryos

Abstract Wheat and barley seeds were subjected to accelerated aging conditions at 12% moisture content and 35°C temperature over 28 days of storage, and to heat-shock treatment carried out by 4 h of incubation at 40°C following 16 h of imbibition at 20°C. Heat-treated, aged seeds showed altered germination behaviour and increasing leakage electroconductivity as well as a reduced incorporation of [35S]-methionine into embryo proteins, in comparison with the corresponding untreated seeds. Two-dimensional electrophoresis of labelled proteins from embryos gave evidence of further quantitative and qualitative changes: (a) ‘normal’ germination protein synthesis in wheat and barley was slightly modified by age, but following heat-shock treatment a general reduction of most of the control polypeptides occurred; (b) heat-shock response resulted in the production of several HSPs with different MW and pl, but a uniform general decline in their synthesis was not observed. Highly labelled HSPs (e.g., those with MW 66.7 or 89.3–66.7 kDa in wheat or barley, respectively) did not change over the entire period of aging, while some smaller HSPs with MW >29 kDa either decreased in intensity or disappeared. Conversely, specific low molecular weight HSPs (MW 17–14.2 kDa) were synthesized more in extremely aged embryos of both species. The hypothesis that these polypeptides may be used as biochemical markers in monitoring both vigour loss and heat-shock induced tolerance in aged seeds is discussed.