Behavior of Lipoxygenase during Establishment, Senescence, and Rejuvenation of Soybean Cotyledons

Lipoxygenase protein and activity were examined during establishment, senescence, and rejuvenation of soybean cotyledons. Lipoxygenase protein, as determined on ;Western' immunoblots, and lipoxygenase-1 and -2/3 activities decreased during mobilization of seed reserves 3 to 9 days following planting. Lipoxygenase-1 activity decreased more rapidly than lipoxygenase-2/3 and was not detectable by 11 days after planting. Lipoxygenase protein increased after day 11 while lipoxygenase-2/3 activity continued to decline. During the later stages of cotyledon senescence, both lipoxygenase protein and lipoxygenase-2/3 activity decreased. Upon rejuvenation, lipoxygenase-2/3 activity, but not that of lipoxygenase-1, increased. These results demonstrate that elevated lipoxygenase activity does not represent a universal characteristic of senescent plant tissue.