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First published online November 26, 2002; 10.1105/tpc.005306 American Society of Plant Biologists A Phytochrome-Associated Protein Phosphatase 2A Modulates Light Signals in Flowering Time Control in Arabidopsis
a Kumho Life and Environmental Science Laboratory, 1 Oryong-dong, Buk-gu, Kwangju 500-712, Korea 3 To whom correspondence should be addressed. E-mail pssong{at}kkpc.com or cmpark{at}snu.ac.kr; fax 82-2-889-1568
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 Fe2+ or Zn2+ 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.
Plant growth and development are not only regulated by intrinsic developmental programs but also are affected greatly by various environmental signals (Fankhauser and Chory, 1997  ). Light is the most critical environmental factor, and it plays two major roles in plants. Plants are photosynthetic and acquire virtually all of the biochemical energy required for survival and propagation solely from light energy. In addition, they constantly monitor the intensity, wavelength, direction, and duration of environmental light. The light signals are integrated subsequently into diverse growth and developmental processes throughout the whole life span, from seed germination to flowering, to achieve optimized growth under a given light condition (Neff et al., 2000; Ma et al., 2001). The light-regulated plant growth and developmental processes collectively are called photomorphogenesis.
Light signaling cascades that govern plant photomorphogenesis have been investigated widely by molecular biological and genetic analyses of various photomorphogenic mutants with altered light responses, mostly in Arabidopsis. A variety of light-signaling mediators, including the photoreceptors, have been identified, and their physiological roles have been elucidated in detail. A currently accepted scheme for plant photomorphogenesis suggests that light signals perceived by the photoreceptors are transmitted through a series of signaling mediators, such as phytochrome-interacting factors (Ni et al., 1998
The red and far-red light–sensing phytochromes and the blue light–sensing cryptochromes are two principal photoreceptors in plant photomorphogenesis. In some cases, an individual photoreceptor is sufficient to trigger a specific light response. However, recent genetic analyses of double and triple photoreceptor mutants have shown that the photoreceptors function in a mode of finely tuned coactions (Neff and Chory, 1998
The phytochrome photoreceptors are light-regulated Ser/Thr-specific protein kinases (Yeh and Lagarias, 1998 In this work, we used a series of molecular biological, genetic, and biochemical approaches to demonstrate that reversible protein phosphorylation is a key component of phytochrome-mediated light signal transduction. A Ser/Thr-specific protein phosphatase 2A (designated FyPP for flower- specific, phytochrome-associated protein phosphatase) associates with and dephosphorylates the phytochromes in a light wavelength–dependent manner. Arabidopsis plants with reduced FyPP levels exhibited early flowering, whereas those with increased FyPP levels flowered later than control plants. The expression patterns of the circadian clock genes were altered accordingly. In agreement with these findings, the FyPP gene was expressed predominantly in floral organs and influenced significantly by daylength. These results indicate that phytochrome-mediated light signals are further modulated by protein phosphorylation/dephosphorylation in flowering time control, providing direct molecular evidence for the function of protein phosphorylation in phytochrome kinase signaling.
Phytochromes Associate with a Protein Phosphatase 2A To search for the protein phosphatase that interacts specifically with the phytochrome kinases, we conducted yeast two-hybrid screens using the C-terminal half (residues 667 to 1122) of the Arabidopsis phytochrome A as bait. We first screened cDNA libraries constructed from Arabidopsis plants but failed to isolate a gene encoding such a phytochrome-interacting protein phosphatase, possibly because its transcript is rare, if it exists, in the mRNA pools used to construct the cDNA libraries. As an alternative, we chose a cDNA library constructed from dark-grown pea seedlings (Kang et al., 2001 ).
Sequence analysis of the positive cDNA clones (his3+ and lacZ+) identified a group of cDNA clones that contained an uninterrupted open reading frame encoding the catalytic subunit of a Ser/Thr-specific protein phosphatase 2A (PP2A). The deduced polypeptide consists of 303 residues with an estimated molecular mass of 34.7 kD (Figure 1)
. It contains all of the structural elements (blocks I to IV) highly conserved among PP2A family members (Virshup, 2000
A putative FyPP gene ortholog also was isolated from Arabidopsis by reverse transcription (RT)–PCR amplification using degenerate primers and poly(A) mRNA (AtFyPP3; Figure 1). It was located on chromosome 3 by sequence comparison with the Arabidopsis genome sequence. Interestingly, further database searches identified one additional Arabidopsis gene on chromosome 1 encoding a polypeptide (designated AtFyPP1) with a sequence identity of >98% to FyPP and AtFyPP3, even with most of the substitutions conserved biochemically among the three FyPP members, such as E69D, I167V, and S219T. The two Arabidopsis polypeptides differ only at two residues, Glu or Asp at position 70 and His or Tyr at position 100 in AtFyPP1 and AtFyPP3, respectively (Figure 1), suggesting that they are FyPP orthologs in Arabidopsis. The phytochrome–FyPP interaction was examined further by yeast coexpression (Figure 2A) and by in vitro pulldown assays using a recombinant FyPP–glutathione S-transferase (GST) fusion protein and purified native oat phytochrome A (Figure 2B) or recombinant Arabidopsis phytochrome B (Figure 2C). Phytochrome B was expressed in Escherichia coli cells and reconstituted in vitro with phycocyanobilin for the assays. AtFyPP3 also was included in the assays to examine the molecular equivalence between FyPP and AtFyPPs. FyPP associated with both phytochromes A and B, but it associated 1.4 times more efficiently with the latter (Figure 2A). AtFyPP3 also associated with the phytochromes in patterns identical to that of FyPP. For in vitro pulldown assays, a FyPP-GST fusion protein, in which the GST was fused to the C terminus of the full-size FyPP, was generated and purified in E. coli cells. The FyPP-GST fusion protein efficiently bound oat phytochrome A (Figure 2B) and phytochrome B (Figure 2C). The AtFyPP3-GST fusion protein also showed identical results (data not shown). Therefore, it is evident that FyPP and its putative Arabidopsis orthologs (AtFyPPs) bind both phytochromes A and B, but with an obvious preference for the latter.
We then examined whether the phytochrome–FyPP interaction was affected by the spectral conformation and phosphorylation status of the phytochromes. FyPP bound the Pfr phytochrome  30% more efficiently than the Pr form. Phytochrome phosphorylation status also influenced the interactions. FyPP associated more efficiently with the phosphorylated phytochromes than with the unphosphorylated forms. Phytochrome B also bound FyPP in similar patterns (Figure 2C). These observations indicate that the phytochrome–FyPP interaction is modulated by light wavelength, signifying a role for FyPP in phytochrome-mediated light signaling.
FyPP Is Localized in the Cytoplasm in Floral Organs
Another clue to FyPP's function was provided by its subcellular localization. Nucleocytoplasmic translocation of the phytochromes is a critical step in phytochrome function. Phytochromes A and B are localized in the cytoplasm under far-red light but translocated into the nucleus under red light (Kircher et al., 1999 ; Nagy et al., 2000). To examine the subcellular localization of FyPP in plant cells, a green fluorescent protein (GFP) coding sequence was fused in frame to the 3' end of the FyPP gene. The FyPP-GFP fusion protein was expressed transiently in Arabidopsis protoplasts. Bright-field and fluorescence microscopy images revealed that FyPP is localized constitutively in the cytoplasm, unlike the phytochromes (Figure 4)
. The GFP-FyPP fusion protein, in which the GFP was fused to the N terminus of the full-size FyPP, and the FyPP-GUS fusion protein also were localized exclusively in the cytoplasm of onion epidermal cells when expressed transiently (data not shown). These observations indicate that FyPP regulates phytochrome phosphorylation in the cytoplasm, which may be important for the nuclear translocation and/or cytoplasmic function of the phytochromes.
Additionally, we observed that the FyPP-GFP and FyPP-GUS fusion proteins were unusually unstable. The fusions were visible for only a short time (<1 h) at 7 to 8 h after particle bombardment, and the fluorescent images disappeared completely after that. These findings suggest that FyPP could become stable as it binds the phytochromes or that the phytochrome–FyPP interaction is a subtle step during phytochrome signaling.
Phytochrome Dephosphorylation by FyPP Is Regulated by Light Wavelength
FyPP efficiently dephosphorylated the phosphorylated oat phytochrome A, but only in the presence of Fe2+ or Zn2+ (Figure 5A)
. Zn2+ was more catalytic than Fe2+ on FyPP activity. By contrast, other cations showed only marginal effects. These results indicate that FyPP is biochemically unique among PP2A family members (Virshup, 2000
We then tried to determine whether FyPP differentially dephosphorylated the Pfr and Pr phytochromes. The Pfr phytochrome was dephosphorylated more readily than the Pr form by FyPP (Figures 5C and 5D). These findings are related to the facts that the Pfr phytochrome is a physiologically active form in most photomorphogenic responses (Roux, 1994 ) and that phosphorylation status is important for phytochrome function (Fankhauser, 2000). AtFyPPs also exhibited the same enzymatic activity and cation requirement as FyPP (data not shown). The oat phytochrome A and FyPP proteins themselves were unaffected under the assay conditions used (Figures 6A and 6B , bar graphs at bottom).
FyPP Modulates Phytochrome Signals in Flowering Time Control To explore the physiological role of the phytochrome–FyPP interaction, a full-size FyPP gene was introduced into Arabidopsis plants in both the sense and antisense orientations, and homozygotic transgenic lines were obtained. FyPP transgenic plants did not show any discernible phenotypic alterations during the seed germination and seedling growth stages. However, adult plants exhibited a marked phenotypic change. Sense transgenic plants displayed delayed flowering, whereas antisense transgenic plants flowered earlier than control plants in long days (Figure 6A). By contrast, in short days, antisense transgenic plants flowered slightly earlier than control plants, but sense transgenic plants were not noticeably different (Figure 6B). These results demonstrate that FyPP plays a major role in the photoperiodic control of flowering time in long days. The specific role of FyPP in flowering time control also is consistent with its predominant expression in floral organs (Figure 3). FyPP transgenic plants did not show any variations in plant morphology and flower architecture other than altered flowering times, indicating that the primary role of FyPP is to control flowering initiation and that it is not involved directly in other growth and developmental processes.
Interestingly, the delayed flowering phenotype of sense transgenic plants was very similar to that of the phytochrome A null mutant (phyA), whereas the accelerated flowering phenotype of antisense transgenic plants was similar to that of the phytochrome B null mutant (phyB) (Bagnall et al., 1995 The high amino acid sequence homology (98%) with FyPP (Figure 1), the specific interactions with the phytochromes in a manner similar to that of FyPP (Figure 2), and the similar expression profiles (Figure 3) all strongly supported the idea that AtFyPPs are structurally and functionally homologous with FyPP. To further examine this possibility, the expression patterns of the FyPP transgene and intrinsic AtFyPP genes were analyzed in FyPP transgenic plants. RT-PCR, rather than RNA gel blot analysis, was used to distinguish their expression, because the two AtFyPP gene sequences share 92% identity. PCR primers were designed based on the sequence regions that are most divergent between the two gene sequences, and the expected sizes of the PCR products also were different from each other: 529 bp for AtFyPP1 and 448 bp for AtFyPP3. In antisense transgenic plants that showed early flowering, the two Arabidopsis genes as well as the FyPP antisense transgene were suppressed drastically (Figure 7A) . By contrast, expression of the intrinsic AtFyPP genes was unaffected in sense transgenic plants. Together with the observation that AtFyPP genes are expressed predominantly in floral organs, like FyPP (Figure 3D), this result indicates that AtFyPPs are functionally equivalent to FyPP.
To demonstrate unequivocally the functional equivalence, an AtFyPP3-deficient Arabidopsis mutant was isolated from a T-DNA insertion pool (ecotype Wassilewskija-2). DNA sequencing revealed that a T-DNA was inserted in the third intron of the AtFyPP3 gene (Figure 7B, top). The absence of AtFyPP3 gene expression in the knockout mutant was verified by RT-PCR (data not shown). The knockout mutant also exhibited an accelerated flowering phenotype (Figure 7B). However, it was not as prominent as that observed in antisense FyPP transgenic plants (Figure 6), possibly because the parental ecotype used to generate the T-DNA insertion pool was Wassilewskija-2, an early-flowering ecotype. Therefore, we conclude that FyPP and its functional orthologs, the AtFyPPs, play a common role in flowering time control.
FyPP Functions Primarily through the Long-Day Flowering Pathway
CONSTANS (CO) gene expression is regulated by the circadian clock with a peak between 12 h after dawn and subsequent dawn (Suárez-López et al., 2001
In addition to altered CO gene expression (Figure 8A), those of other flowering time genes also were influenced (Figure 8B). The transcript levels of the GIGANTEA and FLOWERING LOCUS T (FT) genes increased approximately threefold in antisense transgenic plants but decreased to a detectable level in sense transgenic plants. This finding also is consistent with their roles in flowering (Weigel et al., 1992 ; Bradley et al., 1997; Blázquez and Weigel, 2000).
Recent molecular genetic studies have shown that multiple input signals are integrated via the so-called floral pathway integrators, such as LEAFY (LFY), FT, and AGL20, that are regulated by GA as well as by light (Kobayashi et al., 1999
To determine whether GA or other factors are related to the light signals mediated by the phytochrome–FyPP interaction, the expression of the GA1 and SPY genes involved in GA biosynthesis and signaling (Blázquez, 2000 We then examined whether AtFyPP gene expression was regulated by daylength, as observed with CO gene expression. Interestingly, AtFyPP3 was expressed at a higher level in long days than in short days, like CO, whereas AtFyPP1 did not exhibit such differential expression (Figure 8D). These observations suggest that although AtFyPPs are biochemically equivalent, they play distinct roles in flowering time control. AtFyPP1 may be functional in both long-day and short-day conditions, but AtFyPP3 is required for phytochrome-mediated light signaling specifically in long days. In conclusion, it is evident that a phytochrome kinase–associated PP2A modulates light signals in the photoperiodic control of flowering time in Arabidopsis. The phytochrome–FyPP interaction is specific to the long-day flowering pathway but is not related directly to other genetic pathways in flowering time control. It also is clear that protein phosphorylation is a key molecular event in phytochrome kinase–mediated light signaling in plants, as demonstrated in various eukaryotic kinase signaling pathways.
Phytochrome Kinases Interact Functionally with a PP2A Reversible protein phosphorylation is a feedback-control mechanism in various eukaryotic kinase signaling cascades (Stone et al., 1994 ; Westphal et al., 1998; Keyse, 2000). Recent molecular biological and biochemical evidence indicates that coordinated interactions between coupled protein kinases and phosphatases also play important roles in plants, especially in cell cycle control, in which a set of cyclin-dependent kinases and protein phosphatases are involved (Meszaros et al., 2000; Boniotti and Griffith, 2002). It also has been suggested that protein phosphorylation is an essential step in light signal transduction in plants and that protein phosphatase(s) possibly is involved in this process (Sheen, 1993; Harter et al., 1994; Chandok and Sopory, 1996; Fankhauser, 2000).
The eukaryotic phytochromes are unique red/far-red light receptors in that they perceive environmental light through the N-terminal chromophore binding domain and exert regulatory roles through the C-terminal domain. The C-terminal domain possesses structural elements required for interactions with downstream signaling mediators (Ni et al., 1998
Cryptochrome phosphorylation by the phytochrome kinases is regulated by light wavelength and required for the photoactivation of blue light responses (Ahmad et al., 1998
Our experimental data demonstrate that FyPP and its functional orthologs in Arabidopsis, the AtFyPPs, are protein phosphatases that dephosphorylate the phytochrome kinases, providing molecular evidence for the presence of functional phytochrome kinase–phosphatase coupling in light signal transduction in plants. The phytochrome–FyPP interaction is influenced by the spectral conformation and phosphorylation status of the phytochromes. FyPP binds both phytochromes A and B, but with a relatively higher affinity for the latter (Figure 2). Transgenic plants with overexpressed or suppressed FyPP levels exhibit delayed- or early-flowering phenotypes (Figure 6) that mimic those observed in the phyA or phyB null mutant, respectively. All of these observations suggest that FyPP modulates both phytochrome A and B signals in flowering time control. However, it seems that FyPP has an opposite effect in each signaling pathway, a negative regulatory role in the former and a positive regulatory role in the latter. This finding may be related to the antagonistic roles played by phytochromes A and B in flowering time control (Mockler et al., 1999 It is unlikely that FyPP is the only protein phosphatase that interacts directly with the phytochromes. Because the phytochromes regulate various aspects of plant photomorphogenesis, it is highly possible that more than one protein phosphatase would be involved, each for a specific photomorphogenic process. It will be interesting to determine whether multiple protein phosphatases interact with the same structural motif or with distinct motifs in the phytochrome molecule. This hypothesis reflects the fact that multiple phytochrome-interacting factors with apparently distinct roles interact with the phytochromes.
Reversible Protein Phosphorylation Is a Primary Switch That Initiates Phytochrome Signaling
How does FyPP regulate the phytochrome signals? FyPP is localized in the cytoplasm, indicating that FyPP-mediated dephosphorylation of the phytochromes occurs in the cytoplasm. Phytochrome dephosphorylation by FyPP would mediate the light-induced nuclear localization of the phytochromes, as has been suggested (Ni et al., 1998
The physiologically active Pfr phytochrome is more readily dephosphorylated by FyPP (Figure 5). The Pfr phytochrome with an unphosphorylated Ser-598 residue has a reduced affinity for PKS1 (Fankhauser et al., 1999
FyPP Exerts a Flowering-Specific Role Analyses of transgenic Arabidopsis plants with the FyPP gene demonstrate that the expression level of the FyPP or AtFyPP gene is in inverse proportion to the timing of flowering. Transgenic plants with reduced FyPP levels showed accelerated flowering, whereas those with increased FyPP levels showed delayed flowering, indicating that FyPP negatively regulates flowering initiation. The altered flowering phenotypes observed in antisense and sense transgenic plants are very similar to those seen in the phyA and phyB mutants, respectively (Figure 6). Although the possibility that either phyA or phyB signal is regulated specifically by FyPP still exists, it is more likely that both signals are regulated by FyPP.
Long days represent a critical and sufficient environmental factor that initiates flowering in Arabidopsis. AtFyPP3 is expressed to a higher level in long days than in short days, as observed with CO (Suárez-López et al., 2001
Plant Materials and Growth Conditions Arabidopsis thaliana plants (ecotypes Columbia and Wassilewskija-2) were grown in a controlled culture room at 22°C with a photoperiod of 16 h and RH of 70%. Agrobacterium tumefaciens–mediated transformation was performed by a modified floral-dip method (Clough and Bent, 1998 ). An Arabidopsis AtFyPP3-deficient mutant was isolated from a pool of T-DNA insertion lines (ecotype Wassilewskija-2; Wisconsin Arabidopsis Knockout Facility, Madison, WI). It had a T-DNA insertion in the third intron of the AtFyPP3 gene, as determined by DNA sequencing. For light treatments, plants were grown in the dark or under various light wavelengths. Continuous white light was provided by fluorescent FLR40D/A tubes (Osram, Seoul, Korea) at 15 µmol·m-2·s-1. Red and far-red light (10 and 7 µmol·m-2·s-1, respectively) were provided by red and far-red light-emitting diodes equipped in a red/far-red E-30LED1 growth chamber (Percival Scientific, Boone, IA).
Yeast Two-Hybrid Screening
RNA Gel Blot Analysis and Comparative Reverse Transcription–PCR Comparative reverse transcription (RT)–PCR was used for some quantitative purposes. Total RNA samples were pretreated extensively with RNase-free DNaseI to eliminate contaminating genomic DNA. Primary cDNA was prepared from 2 µg of total RNA using Pfu Turbo polymerase (Stratagene, La Jolla, CA) in a 20-µL reaction volume, and 2 µL of the reaction mixture was used for subsequent RT-PCR in a 50-µL reaction volume. The RT-PCR runs were 15 to 28 cycles, depending on the linear range of PCR amplification for each gene, each cycle at 94°C for 1 min, 58°C for 30 s, and 72°C for 1 min. One additional cycle at 72°C for 7 min was performed after the last run to allow for trimming of incomplete polymerizations.
Preparation of Phytochrome Photoreceptors
The full-size Arabidopsis phytochrome B gene was cloned into the pGEM3Z(+) vector and subsequently subjected to in vitro translation using the TNT Quick Coupled Transcription/Translation System according to the procedure provided by the manufacturer (Promega, Madison, WI). One microgram of template DNA and 20 µCi of 35S-Met (catalog No. AG1094; Amersham, Piscataway, NJ) were used in a 50-µL reaction volume. ATP was included at a final concentration of 1 µM. The reaction mixture was incubated at 30°C for 90 min. In vitro reconstitution with phycocyanobilin (PCB) was performed on ice under green safety light as described (Park et al., 2000b
In Vitro Pulldown Assays
The in vitro pulldown assays were performed essentially as described previously (Kang et al., 2001 In vitro pulldown assays with phytochrome B were performed in a manner similar to those with oat phytochrome A but using 5 µL of the in vitro translation mixture, which had been reconstituted in vitro with PCB.
Protein Phosphatase Assays Upon request, all novel materials described in this article will be made available in a timely manner for noncommercial research purposes.
Accession Numbers
We thank Il-Ha Lee and Jung-Mook Kim for critical reading of the manuscript. We also thank Joanne Chory and Kunhua Chen for scientific communications. This work was supported by Kumho Petrochemical Co., Ltd. (Publication 59), and by grants from the Korea Research Foundation (to C.-M.P.) and the Korea Institute of Science and Technology Evaluation and Planning and Rural Development Administration (to P.-S.S.).
Article, publication date, and citation information can be found at www.plantcell.org/cgi/doi/10.1105/tpc.005306.
1 These authors contributed equally to this work.
2 Current address: Graduate School of Chemistry and Molecular Engineering, Seoul National University, Seoul 151-742, Korea. Received June 13, 2002; accepted September 13, 2002.
Ahmad, M., Jarillo, J.A., Smirnova, O., and Cashmore, A.R. (1998). The CRY1 blue light receptor of Arabidopsis interacts with phytochrome A in vitro. Mol. Cell 1, 939–948.[CrossRef][Web of Science][Medline] Bagnall, D.J., King, R.W., Whitelam, G.C., Boylan, M.T., Wagner, D., and Quail, P.H. (1995). Flowering responses to altered expression of phytochrome in mutants and transgenic lines of Arabidopsis thaliana (L.) Heynh. Plant Physiol. 108, 1495–1503.[Abstract] Blázquez, M., Koornneef, M., and Putterill, J. (2001). Flowering on time: Genes that regulate the floral transition. Workshop on the molecular basis of flowering time control. EMBO Rep. 2, 1078–1082.[CrossRef][Web of Science][Medline]
Blázquez, M.A. (2000). Flower development pathways. J. Cell Sci. 113, 3547–3548. Blázquez, M.A., and Weigel, D. (2000). Integration of floral inductive signals in Arabidopsis. Nature 404, 889–892.[CrossRef][Medline]
Boniotti, M.B., and Griffith, M.E. (2002). "Cross-talk" between cell division and development in plants. Plant Cell 14, 11–16.
Bradley, D., Ratcliffe, O., Vincent, C., Carpenter, R., and Coen, E. (1997). Inflorescence commitment and architecture in Arabidopsis. Science 275, 80–83. Chandok, M.R., and Sopory, S.K. (1996). Phosphorylation/dephosphorylation steps are key events in the phytochrome-mediated enhancement of nitrate reductase mRNA levels and enzyme activity in maize. Mol. Gen. Genet. 251, 599–608.[Medline] Choi, G., Yi, H., Lee, J., Kwon, Y.-K., Soh, M.-S., Shin, B., Luka, Z., Hahn, T.-R., and Song, P.-S. (1999). Phytochrome signaling is mediated through nucleoside diphosphate kinase 2. Nature 401, 610–613.[CrossRef][Medline] Clough, S.J., and Bent, A.F. (1998). Floral dip: A simplified method for Agrobacterium-mediated transformation of Arabidopsis thaliana. Plant J. 16, 735–743.[CrossRef][Web of Science][Medline]
Colon-Carmona, A., Chen, D.L., Yeh, K.C., and Abel, S. (2000). Aux/IAA proteins are phosphorylated by phytochrome in vitro. Plant Physiol. 124, 1728–1738. Fankhauser, C. (2000). Phytochromes as light-modulated protein kinases. Semin. Cell Dev. Biol. 11, 467–473.[CrossRef][Medline] Fankhauser, C., and Chory, J. (1997). Light control of plant development. Annu. Rev. Cell Dev. Biol. 13, 203–229.[CrossRef][Web of Science][Medline] Fankhauser, C., and Chory, J. (1999). Light receptor kinases in plants. Curr. Biol. 9, R123–R126.[Medline]
Fankhauser, C., Yeh, K.-C., Lagarias, J.C., Zhang, H., Elich, T.D., and Chory, J. (1999). PKS1, a substrate phosphorylated by phytochrome that modulates light signaling in Arabidopsis. Science 284, 1539–1541.
Guo, H., Mockler, T., Duong, H., and Lin, C. (2001). SUB1, an Arabidopsis Ca2+-binding protein involved in cryptochrome and phytochrome coaction. Science 291, 487–490.
Harter, K., Frohnmeyer, H., Kircher, S., Kunkel, T., Muhlbauer, S., and Schäfer, E. (1994). Light induces rapid changes of the phosphorylation pattern in cytosol of evacuolated parsley protoplasts. Proc. Natl. Acad. Sci. USA 91, 5038–5042.
Hériché, J.-K., Lebrin, F., Rabilloud, T., Leroy, D., Chambaz, E.M., and Goldberg, Y. (1997). Regulation of protein phosphatase 2A by direct interaction with casein kinase 2 Kang, J.-G., Ju, Y., Kim, D.-H., Chung, K.-S., Fujioka, S., Kim, J.-I., Dae, H.-W., Yoshida, S., Takatsuto, S., Song, P.-S., and Park, C.-M. (2001). Light and brassinosteroid signals are integrated via a dark-induced small G-protein in etiolated seedling growth. Cell 105, 625–636.[CrossRef][Web of Science][Medline] Keyse, S.M. (2000). Protein phosphatases and the regulation of mitogen-activated protein kinase signaling. Curr. Opin. Cell Biol. 12, 186–192.[CrossRef][Web of Science][Medline]
Kircher, S., Kozma-Bognar, L., Kim, L., Adam, E., Harter, K., Schäfer, E., and Nagy, F. (1999). Light quality–dependent nuclear import of the plant photoreceptors phytochrome A and B. Plant Cell 11, 1445–1456.
Kobayashi, Y., Kaya, H., Goto, K., Iwabuchi, M., and Araki, T. (1999). A pair of related genes with antagonistic roles in mediating flowering signals. Science 286, 1960–1962. Koornneef, M., Alonso-Blanco, C., Peeters, A.J.M., and Soppe, W. (1998). Genetic control of flowering in Arabidopsis. Annu. Rev. Plant Physiol. Plant Mol. Biol. 49, 345–370.[CrossRef][Web of Science] Lapko, V.N., Jiang, X.Y., Smith, D.L., and Song, P.-S. (1999). Mass spectrometric characterization of oat phytochrome A: Isoforms and posttransformational modifications. Protein Sci. 8, 1032–1044.[Web of Science][Medline] Lapko, V.N., and Song, P.-S. (1995). A simple and improved method of isolation and purification for native oat phytochrome. Photochem. Photobiol. 62, 194–198.[Medline]
Lee, H., Suh, S.-S., Park, E., Cho, E., Ahn, J.H., Kim, S.-G., Lee, J.S., Kwon, Y.M., and Lee, I. (2000). The AGAMOUS-LIKE 20 MADS domain protein integrates floral inductive pathways in Arabidopsis. Genes Dev. 14, 2366–2376.
Levy, Y.Y., and Dean, C. (1998). The transition to flowering. Plant Cell 10, 1973–1989.
Ma, L., Li, J., Qu, L., Hager, J., Chen, Z., Zhao, H., and Deng, X.W. (2001). Light control of Arabidopsis development entails coordinated regulation of genome expression and cellular pathways. Plant Cell 13, 2589–2607.
Martinez-Hernandez, A., Lopez-Ochoa, L., Arguello-Astorge, G., and Herrera-Estrella, L. (2002). Functional properties and regulatory complexity of a minimal RBCS light-responsive unit activated by phytochrome, cryptochrome, and plastid signals. Plant Physiol. 128, 1223–1233. Más, P., Devlin, P.F., Panda, S., and Kay, S.A. (2000). Functional interaction of phytochrome B and cryptochrome 2. Nature 408, 207–211.[CrossRef][Medline]
Mazzella, M.A., Cerdán, P.D., Staneloni, R.J., and Casal, J.J. (2001). Hierarchical coupling of phytochromes and cryptochromes reconciles stability and light modulation of Arabidopsis development. Development 128, 2291–2299. Meszaros, T., Miskolczi, P., Ayaydin, F., Pettko-Szandtner, A., Peres, A., Magyar, Z., Horvath, G.V., Bako, L., Feher, A., and Dudits, D. (2000). Multiple cyclin-dependent kinase complexes and phosphatases control G2/M progression in alfalfa cells. Plant Mol. Biol. 43, 595–605.[CrossRef][Web of Science][Medline] Mockler, T.C., Guo, H., Yang, H., Duong, H., and Lin, C. (1999). Antagonistic actions of Arabidopsis cryptochromes and phytochrome B in the regulation of floral induction. Development 126, 2073–2082.[Abstract] Nagy, F., Kircher, S., and Schäfer, E. (2000). Nucleo-cytoplasmic partitioning of the plant photoreceptors phytochromes. Semin. Cell Dev. Biol. 11, 505–510.[CrossRef][Web of Science][Medline]
Neff, M.M., and Chory, J. (1998). Genetic interactions between phytochrome A, phytochrome B, and cryptochrome 1 during Arabidopsis development. Plant Physiol. 118, 27–36.
Neff, M.M., Fankhauser, C., and Chory, J. (2000). Light: An indicator of time and place. Genes Dev. 14, 257–271. Neuhaus, G., Bowler, C., Kern, R., and Chua, N.H. (1993). Calcium/calmodulin-dependent and -independent phytochrome signal transduction pathways. Cell 73, 937–952.[CrossRef][Web of Science][Medline] Ni, M., Tepperman, J.M., and Quail, P.H. (1998). PIF3, a phytochrome-interacting factor necessary for normal photoinduced signal transduction, is a novel basic helix-loop-helix protein. Cell 95, 657–667.[CrossRef][Web of Science][Medline] Ni, M., Tepperman, J.M., and Quail, P.H. (1999). Binding of phytochrome B to its nuclear signaling partner PIF3 is reversibly induced by light. Nature 400, 781–783.[CrossRef][Medline]
Okamoto, H., Matsui, M., and Deng, X.W. (2001). Overexpression of the heterotrimeric G-protein
Onouchi, H., Igeño, M.I., Périlleux, C., Graves, K., and Coupland, G. (2000). Mutagenesis of plants overexpressing CONSTANS demonstrates novel interactions among Arabidopsis flowering-time genes. Plant Cell 12, 885–900. Park, C.-M., Bhoo, S.-H., and Song, P.-S. (2000a). Inter-domain crosstalk in the phytochrome molecules. Semin. Cell Dev. Biol. 11, 449–456.[CrossRef][Web of Science][Medline] Park, C.-M., Shim, J.-Y., Yang, S.-S., Kang, J.-G., Kim, J.-I., Luka, Z., and Song, P.-S. (2000b). Chromophore-apoprotein interactions in Synechocystis sp. PCC6803 phytochrome Cph1. Biochemistry 39, 6349–6356.[CrossRef][Medline]
Piñeiro, M., and Coupland, G. (1998). The control of flowering time and floral identity in Arabidopsis. Plant Physiol. 117, 1–8.
Reeves, P.H., and Coupland, G. (2001). Analysis of flowering time control in Arabidopsis by comparison of double and triple mutants. Plant Physiol. 126, 1085–1091. Roux, S.J. (1994). Signal transduction in phytochrome responses. In Photomorphogenesis in Plants, 2nd ed, R.E. Kendrick and G.H.M. Kronenberg, eds (Dordrecht, The Netherlands: Martinus Nijhoff), pp. 187–209.
Samach, A., Onouchi, H., Gold, S.E., Ditta, G.S., Schwarz-Sommer, Z., Yanofsky, M.F., and Coupland, G. (2000). Distinct roles of CONSTANS target genes in reproductive development of Arabidopsis. Science 288, 1613–1616. Sheen, J. (1993). Protein phosphatase activity is required for light-inducible gene expression in maize. EMBO J. 12, 3497–3505.[Web of Science][Medline]
Simpson, G.G., and Dean, C. (2002). Arabidopsis, the Rosetta stone of flowering time? Science 296, 285–289.
Stone, J.M., Collinge, M.A., Smith, R.D., Horn, M.A., and Walker, J.C. (1994). Interaction of a protein phosphatase with an Arabidopsis serine-threonine receptor kinase. Science 266, 793–795. Suárez-López, P., Wheatley, K., Robson, F., Onouchi, H., Valverde, F., and Coupland, G. (2001). CONSTANS mediates between the circadian clock and the control of flowering in Arabidopsis. Nature 410, 1116–1120.[CrossRef][Medline]
Thompson, J.D., Higgins, D.G., and Gibson, T.J. (1994). CLUSTAL W: Improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choice. Nucleic Acids Res. 22, 4673–4680. Virshup, D.M. (2000). Protein phosphatase 2A: A panoply of enzymes. Curr. Opin. Cell Biol. 12, 180–185.[CrossRef][Web of Science][Medline]
Vishnivetskiy, S.A., Paz, C.L., Schubert, C., Hirsch, J.A., Sigler, P.B., and Gurevich, V.V. (1999). How does arrestin respond to the phosphorylated state of rhodopsin? J. Biol. Chem. 274, 11451–11454.
Wang, H., Ma, L.-G., Li, J.-M., Zhao, H.-Y., and Deng, X.W. (2001). Direct interaction of Arabidopsis cryptochromes with COP1 in light control development. Science 294, 154–158. Weigel, D., Alvarez, J., Smyth, D.R., Yanofsky, M.F., and Meyerowitz, E.M. (1992). LEAFY controls floral meristem identity in Arabidopsis. Cell 69, 843–859.[CrossRef][Web of Science][Medline]
Westphal, R.S., Anderson, K.A., Means, A.R., and Wadzinski, B.E. (1998). A signaling complex of Ca2+-calmodulin-dependent protein kinase IV and protein phosphatase 2A. Science 280, 1258–1261.
Yang, H.-Q., Tang, R.-H., and Cashmore, A.R. (2001). The signaling mechanism of Arabidopsis CRY1 involves direct interaction with COP1. Plant Cell 13, 2573–2587.
Yeh, K.C., and Lagarias, J.C. (1998). Eukaryotic phytochromes: Light-regulated serine/threonine protein kinases with histidine kinase ancestry. Proc. Natl. Acad. Sci. USA 95, 13976–13981. This article has been cited by other articles:
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Abstract
INTRODUCTION
Pfr phototransformation of the phytochromes. To obtain clues regarding FyPP's function, FyPP gene expression was examined in different plant organs. It was expressed predominantly in flowers and flowering stems, but the transcript level was relatively very low in other organs (
. Science 276, 952–955.
