GI FLF PHYB SOC1 FT LFY AP1 Flower Identity Genes Clock/Photoperiod Vernalization Sucrose FLC FPA SLY1/GAR2 SNE SPY/GAS1 DDF1 DDF2 RGL1 RGL2 GAI/RGA2 RGA/GRS GA EBS miR159 MYB33 FPF1 EAF1 SHI

Regulation of flowering time in Arabidopsis

 

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flowering pathway

Gibberellin pathway

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The Gibberellin transduction pathway

 

General presentation

 

Gibberellins are plant growth regulators:

Gibberellins (GA) are plant growth regulators, and regulate many developmental processes, such as seed germination, flowering time and stem elongation (See Swain and Singh, 2005).

Several reviews focus on the analysis of the GA signaling in different aspects of plant development: Thornton et al., 1999; Lovegrove and Hooley, 2000; Richards et al., 2001; Sun and Gubler, 2004, Thomas and Sun, 2004.

More information on GA biosynthesis is included here.

The GA transduction pathway:

Gibberellins are activators of flowering time (Langridge, 1957). The gibberellin transduction pathway is one of the 4 main pathways that regulate flowering time determination.

There are 3 types of GA mutants affecting flowering time, with distinct phenotypes:

  • GA biosynthesis mutants: These mutants are impaired in the GA biosynthesis. Among other defects associated with GA deficiency, they are dwarf and late-flowering. However, exogenous GA treatment completely reverts the phenotype. The most commonly used GA biosynthesis mutant is ga1-3.
  • Mutants with increased GA response: These mutants resemble plants treated with an excess of GAs: they are pale early flowering. An example of this class of mutants is spy.
  • Mutants with low GA response: These mutants resemble the ga1 mutants, as they are dwarf and late-flowering. However, the phenotype is not reverted by exogenous GAs. The gai and rga mutants belong to this group.