Regulation of flowering time in Arabidopsis

 

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Flowering pathway

Gibberellin pathway

References

 

The Gibberellin transduction pathway

 

SHI (SHort Internodes)

 

SHI was cloned by Fridborg et al. (2001). See also Fridborg et al., 1999. SHI function is unknown, but it may be a transcription factor: Among other features, it contains a Zn finger and 2 putative nuclear localization sequences (NLS).

SHI is normally expressed in young organs, but in the WT, the SHI transcript was not detected.

SHI is a negative regulator of the GA transduction pathway:

The shi mutants were first obtained by transposon mutagenesis. They are dwarf and flower late, and resemble gai mutants. They also contain high levels of GAs, but are insensitive to GAs. This phenotype is semi-dominant.

In the shi mutants, SHI is over-expressed. When SHI is over-expressed under the control of the 35S promoter, the resulting phenotype is the same as in the shi mutants. SHI is therefore a negative regulator of the GA response.

However, the loss of SHI function give no apparent phenotype. As SHI belongs to a multigene family, its function may be complemented by other genes in the family.