Malate Synthase Activity in Cotton and Other Ungerminated Oilseeds

Abstract

Extracts from several species and varieties of ungerminated cotton [Gossypium barbadense cv. Pima (tetraploid) G. hirsutum cv. Deltapine 16 (tetraploid) G. hirsutum cv. Deltapine 16 (tetraploid) G. herbaceum var. Africanum (diploid) G. hirsutum cv. Stoneville 213 (tetraploid) G. arboreum (diploid) G. thurberi (diploid) G. davidsonii (diploid) G. australe (diploid)] seeds plus homogenates from 18 other oilseeds (representing 11 different families) were examined for malate synthase and isocitrate lyase activity. Malate synthase activities in the various cotton seeds ranged from 35-129% of the units per dry seed weight found in ''Deltapine 16'' cotton. For other oilseeds, the range was from 0.3-58% of ''Deltapine 16'' cotton. Castor bean (Ricinus communis L.) had the least activity per mg dry wt (12-fold lower than the next lowest species), while ''Pima'' cotton (G. barbadense L.) had the highest level (8.53 units). On a per seed basis, these values were 15 and 747 nmol/min. Malate synthase activity was measurable in all seed types examined, whereas isocitrate lyase could not be detected in any of the seeds. Synthesis of malate synthase during seed development may be universal among oilseeds in the absence of glyoxylate-cycle-associated isocitrate lyase activity.