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

Kawamoto N, Sasabe M, Endo M, Machida Y, Araki T - Sci Rep (2015)

Bottom Line: The kinase activity was calcium-dependent.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.

View Article: PubMed Central - PubMed

Affiliation: Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

Expression of CPK6 and CPK33 in backgrounds with altered flowering regulators.Relative levels of CPK6 (a), CPK33 (b), and FLC (c) mRNA in shoot apices. Expression levels were quantified by quantitative RT-PCR analysis. TUBULIN2/3 (TUB) was used as an internal control. Relative levels to that of Col (defined as 1) are indicated. Results of a single set of experiments are shown. Plants were grown under LD condition for 7 days. FRI-Sf2 is a Col line with a FRI allele (FRI-Sf2) from San Feliu-2 accession.
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f6: Expression of CPK6 and CPK33 in backgrounds with altered flowering regulators.Relative levels of CPK6 (a), CPK33 (b), and FLC (c) mRNA in shoot apices. Expression levels were quantified by quantitative RT-PCR analysis. TUBULIN2/3 (TUB) was used as an internal control. Relative levels to that of Col (defined as 1) are indicated. Results of a single set of experiments are shown. Plants were grown under LD condition for 7 days. FRI-Sf2 is a Col line with a FRI allele (FRI-Sf2) from San Feliu-2 accession.

Mentions: Expression of CPK6 and CPK33 in wild-type, FRI-Sf2 (San Feliu-2 allele of FRIGIDA), gigantea (gi), and constans (co) backgrounds were examined by quantitative reverse transcription-PCR (qRT-PCR). In a FRI-Sf2 background, expression of FLOWERING LOCUS C (FLC), a negative regulator of florigen production and response through repression of FT and FD expression41, was greatly up-regulated (Fig. 6). GI and CO are key components of the photoperiod pathway upstream of FT and TSF. Expression of CPK6 and CPK33 was affected in none of the tested backgrounds (Fig. 6), indicating that these genes are not under the control of these regulators of florigen production and response.


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

Kawamoto N, Sasabe M, Endo M, Machida Y, Araki T - Sci Rep (2015)

Expression of CPK6 and CPK33 in backgrounds with altered flowering regulators.Relative levels of CPK6 (a), CPK33 (b), and FLC (c) mRNA in shoot apices. Expression levels were quantified by quantitative RT-PCR analysis. TUBULIN2/3 (TUB) was used as an internal control. Relative levels to that of Col (defined as 1) are indicated. Results of a single set of experiments are shown. Plants were grown under LD condition for 7 days. FRI-Sf2 is a Col line with a FRI allele (FRI-Sf2) from San Feliu-2 accession.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4321167&req=5

f6: Expression of CPK6 and CPK33 in backgrounds with altered flowering regulators.Relative levels of CPK6 (a), CPK33 (b), and FLC (c) mRNA in shoot apices. Expression levels were quantified by quantitative RT-PCR analysis. TUBULIN2/3 (TUB) was used as an internal control. Relative levels to that of Col (defined as 1) are indicated. Results of a single set of experiments are shown. Plants were grown under LD condition for 7 days. FRI-Sf2 is a Col line with a FRI allele (FRI-Sf2) from San Feliu-2 accession.
Mentions: Expression of CPK6 and CPK33 in wild-type, FRI-Sf2 (San Feliu-2 allele of FRIGIDA), gigantea (gi), and constans (co) backgrounds were examined by quantitative reverse transcription-PCR (qRT-PCR). In a FRI-Sf2 background, expression of FLOWERING LOCUS C (FLC), a negative regulator of florigen production and response through repression of FT and FD expression41, was greatly up-regulated (Fig. 6). GI and CO are key components of the photoperiod pathway upstream of FT and TSF. Expression of CPK6 and CPK33 was affected in none of the tested backgrounds (Fig. 6), indicating that these genes are not under the control of these regulators of florigen production and response.

Bottom Line: The kinase activity was calcium-dependent.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.

View Article: PubMed Central - PubMed

Affiliation: Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus