Abstract
Plant roots are essential for overall plant development, growth, and performance by providing anchorage in the soil and uptake of nutrients and water. The primary root of higher plants derives from a group of pluripotent, mitotically active stem cells residing in the root apical meristem (RAM) which provides the basis for growth, development, and regeneration of the root. The stem cells in the Arabidopsis thaliana RAM are surrounding the quiescent center (QC), which consists of a group of rarely dividing cells. The QC maintains the stem cells in a non-cell-autonomous manner and prevents them from differentiation. The necessary dynamic but also tight regulation of the transition from stem cell fate to differentiation most likely requires complex regulatory mechanisms to integrate external and internal cues. Transcription factors play a central role in root development and are regulated by phytohormones, small signaling molecules, and miRNAs. In this review we give a comprehensive overview about the function and regulation of specific transcription factors controlling stem cell fate and root apical meristem maintenance and discuss the possibility of TF complex formation, subcellular translocations and cell-to-cell movement functioning as another level of regulation.
Highlights
Terrestrial plants are sessile organisms and have to adapt to different environmental stimuli by coordinating their growth and development
SHR/SCR act in parallel with PLT to maintain quiescent center (QC) identity and stem cell homeostasis in the Arabidopsis root (Aida et al, 2004)
Cytokinins play a pivotal role in root meristem balance and act antagonistically to auxin. They control the switch from meristematic to differentiated cell fates by suppressing auxin signaling and transport where cells leave the meristematic zone. This is mediated by the AUX/IAA SHORT HYPOCOTYL2 (SHY2), which is activated by cytokinin via ARABIDOPSIS RESPONSE REGULATOR1 (ARR1), but negatively influences auxin signaling and is itself negatively regulated by auxin (Dello Ioio et al, 2007, 2008)
Summary
Terrestrial plants are sessile organisms and have to adapt to different environmental stimuli by coordinating their growth and development . Because of these needs plants have evolved a high degree of developmental and morphological plasticity, which is only possible due to the continuity of plant development (Bradshaw, 1965; Palmer et al, 2012). Plants possess structures called meristems that contain pluripotent stem cells, which are maintained during the whole lifespan of the plant. The RAM and the SAM show different structural organizations, but both meristems harbor stem cells, which continuously generate new cells (Benfey and Scheres, 2000). The stem cells continuously divide asymmetrically generating new stem cells still in contact with the QC cells and daughter cells, undergoing further cell divisions, are shifted further away from the QC and differentiate
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