Methyltransferase Activity in Dry and Germinating Wheat Seedlings

Two methyltransferase systems were investigated in winter wheat (Triticum aestivum ssp. vulgare var. Gaines CI 13448): S-methyl-L-methionine:homocysteine methyltransferase (system 1) and S-adenosyl-L-methionine:methionine methyltransferase (system 2). System 1 was over 10 times as active as system 2 in the dry seed and about five times as active in the soaked seed. Once germination was under way, system 2 showed markedly higher activity, with its highest peaks being followed by peak activity of system 1 during the first 10 days of germination. This sequence was reversed in the root and shoot tissues, with system 1 more active in the early germination period, followed by two peaks of activity of system 2 in both tissues. Protease activity was also assayed over this 14-day germination period. In the seed parts, protease activity was highest just preceding peak activity of system 2. In the root and shoot sections, high protease activity either preceded or coincided with the activity of both systems.