Resumen de Coordination of cell proliferation with developmental programs in Arabidopsis
Postembryonic development in plants constitutes a unique situation to study how the behavior of different cell types is coordinated to form all organs continuously throughout the life of the organism. Specifically, the Arabidopsis root apical meristem (RAM) is an organ, rich in proliferating cells of few cell types organized in concentric layers and with a gradual longitudinal transition from stem cells to differentiated tissues. Using a three-color cell cycle marker developed in our laboratory alongside other experimental strategies, we have begun to characterize cell cycle dynamics in the RAM. We have found that the total cell cycle length and also individual phases change depending on the tissue layers and, most notably, throughout the developmental trajectory. The G1 duration can vary between 1-2 hours in cells about to leave the root meristem and more than 20 hours in cells close to the stem cell niche, following a proximal-distal gradient that coincides with concentrations of the well-studied stem cell regulator PLETHORA (PLT). Here, we have uncovered a link between developmental cues and cell cycle genes. In the regulatory network proposed, PLT proteins act upon RETINOBLASTOMA RELATED 1 (RBR1) phosphorylation by the CDK inhibitor KRP5, lengthening G1 duration by inhibiting G1/S transition.
