Changes of mitochondrial properties in maize seedlings associated with selection for germination at low temperature. Fatty acid composition, cytochrome c oxidase, and adenine nucleotide translocase activities

Mitochondria are affected by low temperature during seedling establishment in maize (Zea mays L.). We evaluated the associated changes in the mitochon drial properties of populations selected for high (C4-H) and low (C4-L) ger mination levels at 9.5 degrees C. When seedlings of the two populations wer e grown at 14 degrees C (near the lower growth limit), the mitochondrial in ner membranes of C4-H showed a higher percentage of 18-carbon unsaturated f atty acids, a higher fluidity, and a higher activity of cytochrome c oxidas e. We found a positive relationship between these properties and the activi ty of a mitochondrial peroxidase, allowing C4-H to reduce lipid peroxidatio n relative to C4-L. The specific activity of reconstituted ATP/ADP transloc ase was positively associated with this peroxidase activity, suggesting tha t translocase activity is also affected by chilling. The level of oxidative stress and defense mechanisms are differently expressed in tolerant and su sceptible populations when seedlings are grown at a temperature near the lo wer growth limit. Thus, the interaction between membrane lipids and cytochr ome c oxidase seems to play a key role in maize chilling tolerance. Further more, the divergent-recurrent selection procedure apparently affects the al lelic frequencies of genes controlling such an interaction.