Kaurene Synthetase Activity in Helianthus annuus L.

In previous studies, the conversion of geranylgeranyl pyrophosphate to ent-kaurene (kaurene synthetase AB activity) could not be detected readily in crude extracts of sunflower (Helianthus annuus L.) seedlings (Shen-Miller, West 1982 Plant Physiol 69: 637-641). These investigations also revealed the presence of inhibitors for Marah macrocarpus kaurene synthetase AB activity in crude extracts of sunflower seedlings. It has now been found that crude extracts prepared from intact sunflower seedlings stored in liquid N(2) for several days have greatly enhanced AB activity in comparison with frozen, but not stored, controls. The levels of activity for the conversion of copalyl pyrophosphate to ent-kaurene (kaurene synthetase B activity) are affected only slightly by storage of intact seedlings in liquid N(2). Extracts from intact seedlings that had been stored in liquid N(2) also showed less inhibitory activity for Marah macrocarpus endosperm kaurene synthetase AB activity.