Gibberellin Signaling Controls Cell Proliferation Rate in Arabidopsis

Abstract

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.

Longitudinal zonation pattern inArabidopsisroot tip defined by a multiple structural change algorithm

“…6A, B), accompanied by an increase in the PD length. However, these results contrast with some previous studies that concluded that wt arabidopsis RAM reaches its maximum size 5 DAG (Dello Ioio et al, 2007;Achard et al, 2009;Moubayidin et al, 2010;Zhou et al, 2011), equivalent to our 7 DAS. This discrepancy about the age at which the RAM reaches its maximum size can be explained by the fact that this age is highly dependent on environmental conditions that vary among studies and by possible methodological differences in meristem length determination.…”

Jasmonate Controls Leaf Growth by Repressing Cell Proliferation and the Onset of Endoreduplication while Maintaining a Potential Stand-By Mode

“…Reinforcing the role of DELLAs as integrators of plant hormone and environmental change responses, recent studies have shown the interaction of DELLAs with JAZ proteins (Hou et al, 2010;Wild et al, 2012;Yang et al, 2012) as well as the MYC2 transcription factor (Hong et al, 2012;Wild et al, 2012). In addition, DELLAs negatively affect plant organ growth by reducing both cell proliferation and cell expansion (Achard et al, 2009). It is then tempting to speculate that JA-triggered growth inhibition could be fine tuned by binding competition among JAZ, DELLA, and MYC2 proteins.…”

“…The cell cycle regulation machinery is tightly coordinated temporally and spatially during plant development by the action of phytohormones (Gutierrez, 2009;Gonzalez et al, 2010;Dudits et al, 2011). Several studies involving plant hormones such as auxin (PerrotRechenmann, 2010), abscisic acid ( Swiątek et al, 2002;Skirycz and Inzé, 2010), brassinosteroids (Clouse, 2011), GAs (Achard et al, 2009), or cytokinins (Haberer and Kieber, 2002) show how hormonal signaling networks are able to modulate cell division parameters to impact plant growth and development.…”

Physiological, morphological and biochemical characteristics of the sexual propagation of Piper aduncum (Piperaceae)

“…Light induces photomorphogenesis, leading to inhibition of hypocotyl growth, whereas GAs promote etiolated growth characterized by increased hypocotyl elongation (Feng et al 2008, Lucas et al 2008. It is well established that GAs promote growth through the hypocotyl cell expansion, stimulating the destruction of DELLA proteins, which are known repressors of GA signaling (Feng et al 2008, Ubeda-Tomás et al 2008, Benková & Hejátko 2009, Achard et al 2009). Although GAs are strong stimulants of shoot growth, they not always accelerate root growth (Tanimoto 2005).…”

“…In P. aduncum was observed a linear decrease in radicle length of normal seedlings with the addition of GA 3 ( figure 20C and D). In the roots of Arabidopsis, GA is an important regulator of growth, promoting both elongation (UbedaTomás et al 2008) and cell proliferation (Achard et al 2009, Ubeda-Tomás et al 2009). GA levels seem to be necessary to promote and maintain the increase in the rate of root growth by controlling the size of the root meristem by means of mitotic activity (Ubeda-Tomas et al 2009).…”