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 alpha-tocopherol as well as of gamma-tocopherol increased significantly.

Jasmonate is involved in the induction of tyrosine aminotransferase and tocopherol biosynthesis in Arabidopsis thaliana.

Coronatine-inducible tyrosine aminotransferase (TAT), which catalyses the transamination from tyrosine to p-hydroxyphenylpyruvate, is the first enzyme of a pathway leading via homogentisic acid to plastoquinone and tocopherols, the latter of which are known to be radical scavengers in plants. TAT can be also induced by the octadecanoids methyl jasmonate (MeJA) and methyl-12-oxophytodienoic acid (MeOPDA), as well as by wounding, high light, UV light and the herbicide oxyfluorfen. In order to elucidate the role of octadecanoids in the process of TAT induction in Arabidopsis thaliana (L.