Gibberellins modulate light signaling pathways to prevent Arabidopsis seedling de-etiolation in darkness.
In many plants, photomorphogenesis is the default developmental program after seed germination, and provides the key features that allow adaptation to light. This program is actively repressed if germination occurs in the absence of light, through a mechanism dependent on the E3 ubiquitin ligase activity that is encoded in Arabidopsis by COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1), which induces proteolytic degradation of transcription factors necessary for light-regulated development, such as HY5 (LONG HYPOCOTYL 5) and HYH (LONG HYPOCOTYL 5 HOMOLOG), and stabilization of transcription factors that promote skotomorphogenesis, such as PIF3 (PHYTOCHROME INTERACTING FACTOR 3). Seedlings deficient in gibberellin (GA) synthesis or signaling display a de-etiolated phenotype when grown in darkness, equivalent to the phenotype of cop1 mutants, which indicates that the switch between photo- and skotomorphogenesis is also under hormonal control. Here we provide evidence for the existence of crosstalk between GA and the COP1-mediated pathway, and identify HY5 and the PIF family as nodes of a regulatory network. This interaction occurs through distinct molecular mechanisms, based on the observation that GA signaling regulates protein stability of HY5, and the activity of PIF3.
Instituto de Biología Molecular y Celular de Plantas (CSIC-UPV), Av de los Naranjos s/n, 46022-Valencia, Spain.
David
D
Alabadí
Javier
J
Gallego-Bartolomé
Leonardo
L
Orlando
Laura
L
García-Cárcel
Vicente
V
Rubio
Cristina
C
Martínez
Martín
M
Frigerio
Juan Manuel
JM
Iglesias-Pedraz
Ana
A
Espinosa
Xing Wang
XW
Deng
Miguel A
MA
Blázquez
D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism*; D003624:Darkness; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005875:Gibberellins / Q000378:metabolism*; D008027:Light; D008954:Models, Biological; D009024:Morphogenesis; D009687:Nuclear Proteins / Q000378:metabolism*; D036226:Seedlings / Q000378:metabolism*; D015398:Signal Transduction
D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D005875:Gibberellins; D009687:Nuclear Proteins; C109254:HY5 protein, Arabidopsis; C116162:PIF3 protein, Arabidopsis