Content area
Full Text
Plant Mol Biol (2009) 69:383396 DOI 10.1007/s11103-008-9393-6
Hormone interactions at the root apical meristem
Eva Benkov Jan Hejtko
Received: 23 May 2008 / Accepted: 27 August 2008 / Published online: 19 September 2008 Springer Science+Business Media B.V. 2008
Abstract Plants exhibit an amazing developmental exibility. Plant embryogenesis results in the establishment of a simple apicalbasal axis represented by apical shoot and basal root meristems. Later, during postembryonic growth, shaping of the plant body continues by the formation and activation of numerous adjacent meristems that give rise to lateral shoot branches, leaves, owers, or lateral roots. This developmental plasticity reects an important feature of the plants life strategy based on the rapid reaction to different environmental stimuli, such as temperature uctuations, availability of nutrients, light or water and response resulting in modulation of developmental programs. Plant hormones are important endogenous factors for the integration of these environmental inputs and regulation of plant development. After a period of studies focused primarily on single hormonal pathways that enabled us to understand the hormone perception and signal transduction mechanisms, it became obvious that the developmental output mediated by a single hormonal pathway is largely modied through a whole network of interactions with other hormonal pathways. In this review, we will summarize recent knowledge on hormonal networks that regulate the development and growth of root with focus on the hormonal interactions that shape the root apical meristem.
Keywords Root meristem Hormonal cross-talk
Abscisic acid Auxin Brassinosteroid Cytokinin
Ethylene Gibberellin Arabidopsis
Introduction: when root grows
The root meristem is an organ of well-dened structure with stereotypical patterns of cell types along radial and longitudinal axes. The radial pattern is organized in concentric rings of lateral root cap, epidermis, ground tissue (cortex and endodermis) and a pericycle surrounding a central stele (Dolan et al. 1993; van den Berg et al. 1998). The radial patterning is laid down during embryogenesis and maintained by stem cell niche activity consisting of four sets of initials: the lateral root cap/epidermal, the cortical/endodermal, the columella and the pericycle/vascular initials surrounding quiescent centre (QC) (Dolan et al. 1993; van den Berg et al. 1998). Stem cells have the capacity for prolonged self-renewal (Watt and Hogan 2000). Each stem cell undergoes an asymmetric division to produce one daughter cell...