Abiotic stress-induced changes in glutathione and thioredoxin h levels in maize

Abstract

The possible relationship between abiotic stress-induced changes in glutathione (GSH) and thioredoxin h (Trx h) levels was investigated in two maize ( Zea mais L.) inbred lines. Less damage was suffered by the chilling-tolerant line Z7 during chilling and by the chilling-sensitive line Penjalinan (Pen) during heat stress, as shown by electrolyte leakage, dry weight and water content data. These parameters were similar in both genotypes during polyethylene glycol (PEG) treatment. Pretreatment with abscisic acid (ABA) reduced the heat-induced increase in electrolyte leakage. A great increase in the GSH and Trx h levels was induced by chilling in Z7 and, conversely, by heat stress in Pen. Extreme temperatures had a similar effect on the level of cysteine and γ-glutamylcysteine (GSH precursors) and on the ratio of reduced to oxidised forms of the three low-molecular-weight thiols, as well as on the activity of glutathione reductase (EC 1.6.4.2). ABA and PEG treatment did not change the GSH content or even decreased it, but increased the Trx h level in both genotypes. A combination of ABA or PEG treatment with heat stress induced similar changes in the GSH and Trx h contents to those induced by heat stress alone. The parallel changes in GSH and Trx h levels at extreme temperatures, and the opposite changes observed during ABA and PEG treatment indicate the stress-specific regulation of their levels during various abiotic stresses.