A phytochrome-associated protein phosphatase 2A modulates light signals in flowering time control in Arabidopsis.
Reversible protein phosphorylation, which is catalyzed by functionally coupled protein kinases and protein phosphatases, is a major signaling mechanism in eukaryotic cellular functions. The red and far-red light-absorbing phytochrome photoreceptors are light-regulated Ser/Thr-specific protein kinases that regulate diverse photomorphogenic processes in plants. Here, we demonstrate that the phytochromes functionally interact with the catalytic subunit of a Ser/Thr-specific protein phosphatase 2A designated FyPP. The interactions were influenced by phosphorylation status and spectral conformation of the phytochromes. Recombinant FyPP efficiently dephosphorylated oat phytochrome A in the presence of Fe(2+) or Zn(2+) in a spectral form-dependent manner. FyPP was expressed predominantly in floral organs. Transgenic Arabidopsis plants with overexpressed or suppressed FyPP levels exhibited delayed or accelerated flowering, respectively, indicating that FyPP modulates phytochrome-mediated light signals in the timing of flowering. Accordingly, expression patterns of the clock genes in the long-day flowering pathway were altered greatly. These results indicate that a self-regulatory phytochrome kinase-phosphatase coupling is a key signaling component in the photoperiodic control of flowering.
Kim
Dae-Hwan
DH
Kumho Life and Environmental Science Laboratory, 1 Oryong-dong, Buk-gu, Kwangju 500-712, Korea.
Kang
Jeong-Gu
JG
Yang
Song-Sook
SS
Chung
Kyung-Sook
KS
Song
Pill-Soon
PS
Park
Chung-Mo
CM
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D003593:Cytoplasm / Q000201:enzymology / Q000235:genetics / Q000528:radiation effects; D035264:Flowers / Q000201:enzymology* / Q000254:growth & development / Q000528:radiation effects; D008027:Light; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000235:genetics* / Q000378:metabolism* / Q000528:radiation effects; D010766:Phosphorylation / Q000528:radiation effects; D017440:Photoperiod; D010834:Phytochrome / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D054648:Protein Phosphatase 2; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D013997:Time Factors
D029681:Arabidopsis Proteins; D010834:Phytochrome; C472137:AtFyPP3 protein, Arabidopsis; C472138:FyPP protein, Arabidopsis; C472136:FyPP1 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2