Heat tolerance together with heat stress-induced changes in glutathione and hydroxymethylglutathione levels is affected by chromosome 5A of wheat

The effect of heat stress on glutathione synthesis was studied in wheat genotypes with different freezing tolerance to establish whether their response to extremely high temperatures also differed. Heat stress resulted in less injury in the freezing-sensitive genotypes compared to the tolerant ones. After heat stress the reduced hydroxymethylglutathione and glutathione contents, the ratio of their reduced to oxidised forms (GSH/GSSG and hmGSH/hmGSSG) and the glutathione reductase activity (GR) were higher and the GSSG and hmGSSG contents lower in the freezing-sensitive genotype compared to the two tolerant ones. Using two 5A chromosome substitution lines developed from the three studied genotypes, the levels of these parameters were similar to those of the donor genotypes. The higher GSH and hmGSH levels in the freezing-sensitive genotypes at high temperatures were the result of the increased synthesis of GSH and hmGSH, as shown by the higher activity of the two enzymes catalysing the synthesis and by the higher incorporation of S-35 from the labelled sulphate into the two thiols. The amount of S-35-containing proteins was also greater in these genotypes. The present observations indicate the regulatory role of the 5A chromosome in GSH and hmGSH synthesis during heat stress in wheat. (C) 2003 Elsevier Ireland Ltd. All rights reserved.