Gibberellin signaling controls cell proliferation rate in Arabidopsis.
Plant growth involves the integration of many environmental and endogenous signals that together with the intrinsic genetic program determine plant size. At the cellular level, growth rate is regulated by the combined activity of two processes: cell proliferation and expansion. Gibberellins (GA) are plant-specific hormones that play a central role in the regulation of growth and development with respect to environmental variability. It is well established that GA promote growth through cell expansion by stimulating the destruction of growth-repressing DELLA proteins (DELLAs); however, their effects on cell proliferation remain unknown. Kinematic analysis of leaf and root meristem growth revealed a novel function of DELLAs in restraining cell production. Moreover, by visualizing the cell cycle marker cyclinB1::beta-glucuronidase in GA-signaling mutants, we show that GA modulate cell cycle activity in the root meristem via a DELLA-dependent mechanism. Accordingly, expressing gai (a nondegradable DELLA protein) solely in root meristem reduced substantially the number of dividing cells. We also show that DELLAs restrain cell production by enhancing the levels of the cell cycle inhibitors Kip-related protein 2 (KRP2) and SIAMESE (SIM). Therefore, DELLAs exert a general plant growth inhibitory activity by reducing both cell proliferation and expansion rates, enabling phenotypic plasticity.
Achard
Patrick
P
Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2357, Conventionné avec l'Université de Strasbourg, 67084 Strasbourg, France.
Gusti
Andi
A
Cheminant
Soizic
S
Alioua
Malek
M
Dhondt
Stijn
S
Coppens
Frederik
F
Beemster
Gerrit T S
GT
Genschik
Pascal
P
D017360:Arabidopsis / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism; D049109:Cell Proliferation; D005875:Gibberellins / Q000378:metabolism*; D018519:Meristem / Q000254:growth & development / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism*; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; C109555:GAI protein, Arabidopsis; D005875:Gibberellins; C407546:ICK2 protein, Arabidopsis; D010937:Plant Growth Regulators; C517317:SIAMESE protein, Arabidopsis