Modulation of Plant Gene Expression by Cytokinins

Abstract

Cytokinins play important roles in plant growth and development. They regulate the synthesis or degradation of proteins and nucleic acids. Specific mRNAs and proteins are up- and down-regulated by the hormones. Regulation of plant gene expression by cytokinins is at the levels of transcription and post-transcription. Expression of a single gene can be modulated by the interaction of two hormones since the levels of cytokinin-enhanced nitrate reductase transcript are reduced by abscisic acid. Relatively high-affinity cytokinin-binding proteins have been isolated, but the physiological role of the binding proteins remains unknown. Examination of X-ray crystal structures of cytokinin molecules indicates that correct stereochemical conformation is required for a biologically active cytokinin. Using available genetic, immunological, biochemical and recombinant DNA techniques, some questions regarding the mechanisms of cytokinin action may be answered in the near future.