Tocopherol content and activities of tyrosine aminotransferase and cystine lyase in Arabidopsis under stress conditions

Tocopherols are presumed to be important antioxidants and scavengers of lipid radicals and reactive oxygen species in plants. Age is known to be a condition under which oxidative stress increases. In leaves of aging Arabidopsis thaliana plants, the content of α-tocopherol as well as of γ-tocopherol increased significantly. The activity of tyrosine aminotransferase, which supplies the biosynthetic pathway with 4-hydroxyphenylpyruvate, was increased as well. On the other hand, coronatine, a phytotoxin mimicking octadecanoids and leading to symptoms of senescence, caused a moderate increase in α-tocopherol as well as some enhancement of γ-tocopherol.