Relationship between alcohol dehydrogenase activity and low-temperature in two maize genotypes, Silverado F1 and Adh1-Adh2- doubly null.

We have examined the role of alcohol dehydrogenase (ADH, E.C.1.1.1.1) in chilling tolerance using maize (Zea mays L.) Adh1(-)Adh2(-) doubly null mutant. Adh1(-)Adh2(-) doubly null seedlings were found to have lowered survival rates compared to non-doubly null maize seedlings (Silverado F(1)) when held at 2 degrees C for varying periods. Exposure to ethanol did not increase the chilling tolerance in either Silverado F(1) or Adh1(-)Adh2(-) doubly null. ADH activity in Silverado F(1) remained steady when held at 2 degrees C for up to 3 d. ADH1 protein accumulation in chilled Silverado F(1) seedlings remained unchanged throughout the period of cold exposure. Chilling led to a significant inhibition of the P-H(+)-ATPase (E.C. 3.6.3.6) activity in Adh1(-)Adh2(-)doubly null, but minimal inhibition was seen in Silverado F(1). Though P-H(+)-ATPase activity in Adh1(-)Adh2(-) decreased, P-H(+)-ATPase protein levels remained constant during the chilling period. Levels of ATP slightly fluctuated in both types of seedlings during the duration of chilling. Lipid peroxidation levels in Adh1(-)Adh2(-) doubly null increased with chilling exposure, but not in the Silverado F(1). We suggest that ADH activity may play a role in chilling tolerance that is not related to maintenance of glycolysis and ATP production as has been observed during oxygen depravation.