Rapid Effects of IAA on Cell Surface Proteins from Intact Carrot Suspension Culture Cells

Abstract

Suspension cultures of carrot (Daucus carrota L.) which had an absolute requirement for exogenously supplied auxin were grown in medium containing indoleacetic acid (IAA) as the sole auxin source. Putative cell surface proteins were extracted from the intact cells. Resupply of IAA to cultures partially depleted of auxin resulted in rapidly increased activities of three enzyme activities subsequently extracted. Two of the enzyme activities which increased, peroxidase and pectinesterase, have been implicated in the literature as important to cell wall development, structure, and growth. The other enzyme activity which was increased, IAA oxidase, may be involved in the degradation of IAA In vivo. Polypeptides in the extracts were found to increase equally as rapidly as the enzymes in response to IAA as determined with sodium dodecyl sulfate-polyacrylamide electrophoretic gels stained with silver. It is not known whether the changes in enzyme and polypeptide levels in the protein extracts were due to auxin effects on protein synthesis, transport, or extractability.