ABSTRACT

Cytokinins were discovered in the 1950s by their ability to promote cell division in cultured plant cells. Recently, there have been significant breakthroughs in our understanding of the biosynthesis, metabolism, perception and signal transduction of this phytohormone. These advances, coupled with physiological and other approaches, have enabled remarkable progress to be made in our understanding of the interactions between cytokinin function and environmental inputs. In this review, we first highlight the most recent advances in our understanding of cytokinin biosynthesis, metabolism and signalling. We then discuss how various environmental signals interact with these pathways to modulate plant growth, development and physiology.

Key-words: abiotic stress; light; nutrients; signal transduction

INTRODUCTION

Cytokinins were first identified as factors that promoted the proliferation of cultured plant cells (Miller et al. 1955, 1956). Subsequently, this phytohormone was linked to numerous aspects of plant growth and development, including seed germination, vasculature development, meristem function, apical dominance and leaf senescence (Mok & Mok 2001). Much progress has been made recently in our understanding of cytokinin biosynthesis and signalling, and how environmental cues interact with these components to modulate plant growth, development and physiology. In this review, we will first discuss cytokinin biosynthesis, metabolism and signalling, and with an emphasis on recent findings, we will then discuss the role of cytokinin in the assimilation of various macronutrients, the crosstalk with light signalling and, finally, the interactions of cytokinin with abiotic and biotic factors. For additional information, the reader should see recent detailed reviews of cytokinin biosynthesis and metabolism (Sakakibara 2006; Hirose et al. 2008) and signalling (Ferreira & Kieber 2005; Choi & Hwang 2007; Müller & Sheen 2007; To & Kieber 2007).

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