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Plant Cell Rep (2013) 32:771780 DOI 10.1007/s00299-013-1436-z
REVIEW
Cytokinins rsum: their signaling and role in programmed cell death in plants
A. Kunikowska A. Byczkowska M. Doniak
A. Kamierczak
Received: 20 December 2012 / Revised: 22 March 2013 / Accepted: 25 March 2013 / Published online: 12 April 2013 The Author(s) 2013. This article is published with open access at Springerlink.com
Abstract Cytokinins (CKs) are a large group of plant hormones which play a crucial role in many physiological processes in plants. One of the interesting functions of CKs is the control of programmed cell death (PCD). It seems that all CKs-dependent phenomena including PCD are accompanied by special multi-step phosphorelay signaling pathway. This pathway consists of three elements: histidine kinase receptors (HKs), histidine phosphotransfer proteins (HPs) and response regulators (RRs). This review shows the rsum of the latest knowledge about CKs signaling pathways in many physiological processes in plants with special attention paid to PCD process.
Keywords Cytokinin Cytokinin signaling Kinetin
PCD
Introduction
Programmed cell death (PCD) is a process that normally occurs during seed germination, development and senescence. This process is crucial for proper functioning of all multicellular organisms, both plants and animals (Kunikowska et al. 2012; Carimi et al. 2003; Collazo et al. 2006). The latest knowledge classies PCD process on the
basis of changes in cell morphology (van Doorn et al. 2011). In animals, apoptosis, autophagy and necrosis are distinguished. In plants, categorization of cell death is more complicated but in 2011 van Doorn et al. proposed the application of morphological criteria to recognize plant cell death thus vacuolar, necrotic and mixed or atypical forms of cell death. Another classication system was also proposed to describe plant PCD. It includes two classes of cell death called autolytic and non-autolytic which describe processes that occur in intact plants but not in cell cultures (van Doorn 2011).
However, both in animals and plants, changes in the nucleus morphology, especially chromatin condensation and degradation, are the major common morphological features (van Doorn 2011).
Programmed cell death is dened as the genetically determined suicide of individual cells in response to pathogens, environmental stress, and during normal development (Gladish et al. 2006; Collazo et al. 2006) it may be also exogenously induced (Carimi et al. 2003, 2004;...