Two complementary approaches were used to determine the effects of heat shock on wheat-grain quality. Heat-susceptible (cv. Wyuna) and heat-tolerant (cv. Fang) cultivars of wheat were compared after heat shock, utilising both dough-quality testing and proteome analysis. Plants were grown at day/night temperatures of 24/18°C during development, with stressed plants being subjected to heat shock at day/night temperatures of 40/25°C on 15, 16 and 17 days post-anthesis. Grain samples were taken during development (17 days post-anthesis) and at maturity (45 days post-anthesis). Dough-quality testing of flour indicated that the Wyuna cultivar exhibited a decrease in dough strength after heat shock, whilst the Fang cultivar exhibited an increase. Proteome studies conducted on endosperm (at 17 days post-anthesis) showed that the heat-tolerant Fang cultivar exhibited a stronger and more diverse 'heat shock response' than Wyuna. In total, 48 protein spots exhibiting differential expression between control and heat shock treatments were excised from gels and analysed by mass spectrometry. The resultant tryptic-peptide mass fingerprint data was submitted to SWISS-PROT and TrEMBL databases for protein identification. The majority of heat-shock associated proteins had low molecular mass and showed database similarity to previously characterised small heat shock proteins. Several discrete isoforms of the low molecular weight heat shock proteins were observed as differentially expressed between the two cultivars. Furthermore, seven protein spots were expressed in heat shocked Fang but not in heat shocked Wyuna, thus were further characterised utilising tandem mass spectrometry. These possible marker proteins for heat-tolerance may assist breeders in the selection of heat-tolerant cultivars that would not be expected to lose dough strength in such an environment.
- Heat shock