Recent advances in the study of mechanisms of action of phytohormones.

This review highlights recent advances in studies of mechanisms underlying the effects of five phytohormone groups: auxin, cytokinin, gibberellin, abscisic acid, and ethylene. The review summarizes data on receptors of all these phytohormones and the hormone signal transduction systems, which include second messengers, hormone-dependent trans-factors, and the genes controlled by these factors. The effects of phytohormones involve not only induction of novel protein synthesis via activation of their gene expression, but also degradation of repressor proteins through the ubiquitin system. The review contains examples of successful use of data on genes encoding enzymes of phytohormone synthesis and their receptors for development of transgenic plants with particular hormonal characteristics that provide practically valuable traits.