Plant Physiol, November 2001, Vol. 127, pp. 1147-1156

Increasing the Glutathione Content in a Chilling-Sensitive Maize Genotype Using Safeners Increased Protection against Chilling-Induced Injury¹

Institute for Plant Sciences, University of Berne, Altenbergrain 21, CH-3013 Berne, Switzerland (G.K., P.v.B., A.R., C.B.); and Agricultural Research Institute of the Hungarian Academy of Sciences, P.O. Box 19, H-2462 Martonvásár, Hungary (G.K., G.S., G.G.)

With the aim of analyzing their protective function against chilling-induced injury, the pools of glutathione and its precursors, cysteine (Cys) and -glutamyl-Cys, were increased in the chilling-sensitive maize (Zea mays) inbred line Penjalinan using a combination of two herbicide safeners. Compared with the controls, the greatest increase in the pool size of the three thiols was detected in the shoots and roots when both safeners were applied at a concentration of 5 µM. This combination increased the relative protection from chilling from 50% to 75%. It is interesting that this increase in the total glutathione (TG) level was accompanied by a rise in glutathione reductase (GR; EC 1.6.4.2) activity. When the most effective safener combination was applied simultaneously with increasing concentrations of buthionine sulfoximine, a specific inhibitor of glutathione synthesis, the total -glutamyl-Cys and TG contents and GR activity were decreased to very low levels and relative protection was lowered from 75% to 44%. During chilling, the ratio of reduced to oxidized thiols first decreased independently of the treatments, but increased again to the initial value in safener-treated seedlings after 7 d at 5°C. Taking all results together resulted in a linear relationship between TG and GR and a biphasic relationship between relative protection and GR or TG, thus demonstrating the relevance of the glutathione levels in protecting maize against chilling-induced injury.