Gibberellin metabolism and regulation of α -amylase isoenzymes in higher plants

Abstract

So far S2 gibberellins (GA) have been isolated from fungi and higher plants. Structural elucidation, biogenetiG sequence of the intermediates and the nature of regulating enzymes involved in t.he biosynthesis of GA from their precursors, are well established. The pathways from mevalonic acid (MVA) to GAla-aldehyde are common in fungi and higher plants and then differ depending upon the order of hydroxylation. The structural requirement for specific biological function of GA is well established. Numerous conventional methods and newer approaches are used for tentative identification and quantitation of GA metabolites. 2pAhydroxylation and glycosylation of GAs are correlated with seed development, maturation and storage of GAs in inactive forms. The subsequent release of active GAs during germination follows the enzymatic hydrolysis of the endogenous ones. However, environmental stresses have deleterious effects on GA metabolism; in radiated seeds reduced GA formation during gennination adversely affects GA-controlled metabolic processes such as seedling growth and develepment of alpha-amYlase isoenzymes. Physiological aspects of the role of GA in breaking dorman germination and in protein, carborsdrate and lipid metabolism have been discussed. The normal role of GA in biogenesis of alpha-amylase and its isoenzymes have been outlined in detail Recently. mediation of GAs in organelle biogenesis and in the formation of subcellular bk,mernbranes, has been envisaged.