Effect of Gibberellin on Growth, Protein Secretion, and Starch Accumulation in Maize Endosperm Suspension Cells

The physiologic effect of gibberellins (GA) in seed development is poorly understood. We examined the effect of gibberellic acid (GA3) on growth, protein secretion, and starch accumulation in cultured maize (Zea mays L.) endosperm suspension cells. GA3 (5 and 30 μm) increased the fresh weight, dry weight, and protein content of the cultured cells, but the effect of GA3 at 50 μm was not significantly different. However, the protein content in the culture medium was increased by these three concentrations of GA3. The effect of GA3 on the amount of cellular structural polysaccharides was not significant, but GA3 had a dramatic effect on the starch content. At 5 μm, GA3 caused an increase in the starch content, but at 50 μm the starch accumulation was reduced. Chlorocholine chloride (CCC), an inhibitor of GA biosynthesis, significantly increased the starch content and decreased the structural polysaccharide content of the cultured cells. The effects of CCC at 500 μm on the starch and polysaccharide content were partially reversed by 5 μm GA3 applied exogenously. Based on these results we suggest that GA does not favor starch accumulation in the cell cultures and that the addition of lower concentrations of GA3 in the medium may provide an improved balance among the endogenous GA in the cultured cells.