Auxin-regulated changes in protein phosphorylation in pea epicotyls

Auxins regulate various aspects of plant growth and development. However, the mechanism by which these hormones elicit diverse physiological processes is not clear. We present evidence for the role of auxin in protein phosphorylation and the possible involvement of calmodulin in auxin-induced changes. In the presence of auxin, phosphorylation of 23,000, 82,000, 105,000 and 110,000 molecular weight polypeptides markedly decreased whereas phosphorylation of 19,000, 24,000 and 28,000 molecular weight polypeptides increased. These results open up a new experimental approach in understanding the molecular mechanism by which auxins regulate various physiological processes in plants.