CHANGES IN LIPOXYGENASE ISOZYME LEVELS DURING SOYBEAN EMBRYO DEVELOPMENT

Most soybean (Glycine max Merr.), cultivars accumulate three isozymes of lipoxygenase during embryo development. Studies were conducted to determine the levels of expression and accumulation of the individual lipoxygenase isozymes throughout the development of soybean axes and cotyledons. Type 1 lipoxygenase activity (activity at pH 9.0 indicative of lipoxygenase 1) was not detectable in axes or cotyledons from seeds < 6-7 mm in length, but lipoxygenase 1 activity and protein reached high levels at subsequent developmental stages. Type II activity (activity at pH 6.8 indicative of lipoxygenases 2 + 3) was detectable throughout development, with low levels early in development and high levels being present concommitant with lipoxygenase 1. The type II lipoxygenase activity in embryo tissues of seeds < 6-7 mm in length was apparently not du to lipoxygenases 2 and/or 3. Levels of all three lipoxygenase activity isozymes were coordinately regulated during soybean embryo development with higher levels generally expressed in axes than in cotyledons. The expression of these lipoxygenase isozymes appears similar to that of storage proteins and is coincident with the development of germination capability of soybean seeds.