Title : COP9 SIGNALOSOME 5A protein interacts with FLOWERING LOCUS T (FT) and mediates ambient temperature-dependent degradation of FT protein
Abstract:
COP9 signalosome 5A (CSN5A) plays an important role in the protein degradation by ubiquitination. In order to investigate the role of CSN5A in ambient temperature responsive flowering, we analyzed the flowering phenotype of csn5a mutants, The csn5a-1 mutants, completely devoid of CSN5A expression, flowered early at 16°C under long-day conditions, but they showed a normal flowering time phenotype at 23°C under the same conditions. FLOWERING LOCUS T (FT) transcript levels were unaltered in csn5a-1 mutants excluding a possibility that CSN5A regulates FT transcription. However, we found that FT protein abundance was increased in csn5a-1 mutants at 16°C, comparing to wild-type plants, suggesting that FT protein stability is regulated by CSN5A at lower temperatures. A peptide array experiment and co-immunoprecipitation assays identified tyrosine 225 residue in CSN5A was important for the CSN5A-FT interaction. Taken together, we propose that CSN5A regulates the ambient temperature- dependent FT protein degradation.
