Calcium-dependent protein kinases responsible for the phosphorylation of a bZIP transcription factor FD crucial for the florigen complex formation

Appropriate timing of flowering is critical for reproductive success and necessarily involves complex genetic regulatory networks. A mobile floral signal, called florigen, is a key molecule in this process, and flowering locus T (FT) protein is its major component in Arabidopsis. FT is produced in l...

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Bibliographic Details
Published in:Scientific reports 2015-02, Vol.5 (1), p.8341-8341, Article 8341
Main Authors: Kawamoto, Nozomi, Sasabe, Michiko, Endo, Motomu, Machida, Yasunori, Araki, Takashi
Format: Article
Language:English
Subjects:
14-3-3 protein
Arabidopsis - genetics
Arabidopsis - metabolism
Arabidopsis Proteins - biosynthesis
Arabidopsis Proteins - genetics
Arabidopsis Proteins - metabolism
Breeding success
Calcium
Calcium-Calmodulin-Dependent Protein Kinases - biosynthesis
Calcium-Calmodulin-Dependent Protein Kinases - genetics
Flowers - genetics
Flowers - metabolism
Gene Expression Regulation, Enzymologic - physiology
Gene Expression Regulation, Plant - physiology
Kinases
Leucine zipper proteins
Meristem - genetics
Meristem - metabolism
Phosphorylation
Phosphorylation - physiology
Plant Shoots - genetics
Plant Shoots - metabolism
Protein kinase
Proteins
Threonine
Transcription factors
Transcription Factors - genetics
Transcription Factors - metabolism
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Summary:Appropriate timing of flowering is critical for reproductive success and necessarily involves complex genetic regulatory networks. A mobile floral signal, called florigen, is a key molecule in this process, and flowering locus T (FT) protein is its major component in Arabidopsis. FT is produced in leaves, but promotes the floral transition in the shoot apex, where it forms a complex with a basic region/leucine-zipper (bZIP) transcription factor, FD. Formation of the florigen complex depends on the supposed phosphorylation of FD; hitherto, however, the responsible protein kinase(s) have not been identified. In this study, we prepared protein extracts from shoot apices of plants around the floral transition, and detected a protein kinase activity that phosphorylates a threonine residue at position 282 of FD (FD T282), which is a crucial residue for the complex formation with FT via 14-3-3. The kinase activity was calcium-dependent. Subsequent biochemical, cellular, and genetic analyses showed that three calcium-dependent protein kinases (CDPKs) efficiently phosphorylate FD T282. Two of them (CPK6 and CPK33) are expressed in shoot apical meristem and directly interact with FD, suggesting they have redundant functions. The loss of function of one CDPK (CPK33) resulted in a weak but significant late-flowering phenotype.
ISSN:2045-2322
2045-2322
DOI:10.1038/srep08341