Cytokinins, A classical multifaceted hormone in plant system

Today, owing to the versatile functionality and physiological importance of the phytohormone cytokinin (Ck) is a major focus of attention in contemporary wide areas of plant science. Cytokinins (Cks) have implicated in diverse essential processes of plant growth and development as well as in regulation of key genes responsible for the metabolism and activities of plants. Cytokinin interact in a complex manner to control a myriad of aspects related to growth, development and differentiation and its deficiency also causes pleiotropic developmental changes such as reduced shoot and increased root growth. Cytokinin signaling involves His Kinase receptors that perceive cytokinin and transmit the signal via a multi-step phosphorelay similar to bacterial two-component signaling system. Also, this review present a scheme for homeostatic regulation of endogenous cytokinins level in terms of the described mechanism of cytokinin action including its receptors and steps involved in regulation of gene expression at the post-transcriptional level and its role in whole plant as well as cell division. In addition, we also demonstrate a wide variety of biological effects including those on gene expression, inhibition of auxin action, stimulation of cell cycle etc.