Dimers of the N-terminal domain of phytochrome B are functional in the nucleus

Matsushita, Tomonao; Mochizuki, Naoki; Nagatani, Akira

doi:10.1038/nature01837

Cited by 286 publications

(368 citation statements)

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“…To evaluate the contribution of cytoplasmic P fr signaling into the circadian system, we introduced the G767R mutation into the YHB allele (YHB-G767R). Phys containing the G767R mutation are retained in the cytoplasm (Wagner and Quail, 1995;Ni et al, 1999;Matsushita et al, 2003). This has been attributed to the inability of the G767R mutant to interact with PIF3 and then be imported into the nucleus (Pfeiffer et al, 2012).…”

Section: Cytosolic Yhb Has Little Effect On Clock Gene Expression or mentioning

confidence: 99%

A Constitutively Active Allele of Phytochrome B Maintains Circadian Robustness in the Absence of Light

Jones

Litthauer

et al. 2015

Plant Physiology

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The sensitivity of the circadian system to light allows entrainment of the clock, permitting coordination of plant metabolic function and flowering time across seasons. Light affects the circadian system via both photoreceptors, such as phytochromes and cryptochromes, and sugar production by photosynthesis. In the present study, we introduce a constitutively active version of phytochrome B-Y276H (YHB) into both wild-type and phytochrome null backgrounds of Arabidopsis (Arabidopsis thaliana) to distinguish the effects of photoreceptor signaling on clock function from those of photosynthesis. We find that the YHB mutation is sufficient to phenocopy red light input into the circadian mechanism and to sustain robust rhythms in steady-state mRNA levels even in plants grown without light or exogenous sugars. The pace of the clock is insensitive to light intensity in YHB plants, indicating that light input to the clock is constitutively activated by this allele. Mutation of YHB so that it is retained in the cytoplasm abrogates its effects on clock function, indicating that nuclear localization of phytochrome is necessary for its clock regulatory activity. We also demonstrate a role for phytochrome C as part of the red light sensing network that modulates phytochrome B signaling input into the circadian system. Our findings indicate that phytochrome signaling in the nucleus plays a critical role in sustaining robust clock function under red light, even in the absence of photosynthesis or exogenous sources of energy.

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Section: Cytosolic Yhb Has Little Effect On Clock Gene Expression or mentioning

confidence: 99%

A Constitutively Active Allele of Phytochrome B Maintains Circadian Robustness in the Absence of Light

Jones

Litthauer

et al. 2015

Plant Physiology

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“…Autophosphorylation is a common property of all photosensory pigments including phytochromes and phototropins (Christie 2007). However, it also appears that the autokinase activity is dispensable for both phytochrome (Matsushita et al 2003) and phototropin (Kagawa et al 2004) functions. It was found that both AtCRY1 and AtCRY2 are phosphorylated in vivo upon blue light exposure (Shalitin et al 2002;.…”

Section: Protein-protein Interactionsmentioning

confidence: 99%

Structure and Function of Animal Cryptochromes

Öztürk

Song²,

Özgür³

et al. 2007

Cold Spring Harbor Symposia on Quantitative Biology

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Cryptochrome (CRY) is a photolyase-like flavoprotein with no DNA-repair activity but with known or presumed blue-light receptor function. Animal CRYs have DNA-binding and autokinase activities, and their flavin cofactor is reduced by photoinduced electron transfer. In Drosophila, CRY is a major circadian photoreceptor, and in mammals, the two CRY proteins are core components of the molecular clock and potential circadian photoreceptors. In mammals, CRYs participate in cell cycle regulation and the cellular response to DNA damage by controlling the expression of some cell cycle genes and by directly interacting with checkpoint proteins. in response to blue light (Koornneef et al. 1980), was isolated and sequenced, it revealed high sequence homology with Escherichia coli photolyase, and hence, it was in retrospect, correctly speculated that HY4 encoded a blue light photoreceptor and not a signal transducer involved in blue light response (Ahmad and Cashmore 1993). Later, this protein was named cryptochrome 1 (Lin et al. 1995, and a second Arabidopsis protein that has high homology with CRY1 identified by genomics was named CRY2 . The role of CRY in Arabidopsis growth (CRY1) and differentiation (CRY2) was well established by 1995 (see Guo et al. 1998). However, as late as 1997, it was thought that CRY had no role in circadian photoreception in plants (Millar and Kay 1997).The first report implicating CRY in the circadian clock of any organism, plant or animal, came about from the study of DNA repair, in particular, the repair of UV damage in humans by photolyase. This issue had been controversial for nearly 25 years when Li et al. (1993) conducted an exhaustive study with a highly specific and sensitive assay, concluding that humans, like all placental mammals, lacked photolyase (Li et al. 1993). However, a 1995 release of a human expressed sequence tag (EST) list contained a "photolyase ortholog" entry (Adams et al. 1995). In light of this finding and the discovery of a photolyase in Drosophila and rattlesnake (Todo et al. 1993Kim et al. 1996) that repairs the minor UV-induced lesion, the (6-4) photoproduct, in contrast to the classic photolyase that repairs cyclobutane pyrimidine dimers (CPDs), the earlier conclusion regarding the lack of photolyase in humans needed reevaluation. This was done by Hsu et al. (1996) who, in addition to the "photolyase ortholog" in public databases, discovered a second human photolyase gene. Human cells expressing both genes and recombinant proteins encoded by both genes were tested for CPD and (6-4) photolyase activities and were found to lack both. Moreover, the proteins encoded by these genes, like most photolyases (Johnson et al. 1988) and Arabidopsis CRY (Lin et al. 1995; Malhorta et al. 1995), contained FAD (flavin-adenine dinucleotide) and a pterin cofactor. Therefore, it was concluded that these proteins were not repair enzymes but that, like Arabidopsis CRYs, they performed non-repair-related blue light functions and were named human CRY1 and 2 (Hsu et al. 1996). In humans ...

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confidence: 99%

“…Most loss-of-function phyB alleles are defective in phyB localization to large photobodies and are taller than the wild type (Kircher et al, 2002;Chen et al, 2003;Matsushita et al, 2003;Nito et al, 2013), whereas in gain-of-function phyB mutants, phyB localizes to large photobodies under dim light and hypocotyl elongation is more restricted than in the wild type (Ádám et al, 2011;Medzihradszky et al, 2013;Zhang et al, 2013). In the most extreme case, phyB Y276H (YHB), a constitutively active phyB mutant, localizes to large photobodies regardless of light conditions and can inhibit hypocotyl growth even in the dark (Su and Lagarias, 2007).…”

mentioning

confidence: 99%

“…Studies of photobody localization using Arabidopsis phyB have shown that the C-terminal domain of phyB is involved in dimerization and is sufficient for both nuclear and photobody localization (Matsushita et al, 2003;Chen et al, 2005). When the C-terminal domain of phyB is replaced with a dimerization domain, a Simian Vacuolating Virus40 nuclear localization signal, and GFP, the chimeric protein, NGB (for the N-terminal half of phyB fused to GFP), does not localize to photobodies (Matsushita et al, 2003). However, NGB is hyperactive in inhibiting hypocotyl growth in the light, suggesting that photobodies are dispensable and might even play a negative role in the photoinhibition of hypocotyl elongation in the light (Matsushita et al, 2003;Palágyi et al, 2010).…”

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confidence: 99%

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Photobody Localization of Phytochrome B Is Tightly Correlated with Prolonged and Light-Dependent Inhibition of Hypocotyl Elongation in the Dark

et al. 2014

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Photobody localization of Arabidopsis (Arabidopsis thaliana) phytochrome B (phyB) fused to green fluorescent protein (PBG) correlates closely with the photoinhibition of hypocotyl elongation. However, the amino-terminal half of phyB fused to green fluorescent protein (NGB) is hypersensitive to light despite its inability to localize to photobodies. Therefore, the significance of photobodies in regulating hypocotyl growth remains debatable. Accumulating evidence indicates that under diurnal conditions, photoactivated phyB persists into darkness to inhibit hypocotyl elongation. Here, we examine whether photobodies are involved in inhibiting hypocotyl growth in darkness by comparing the PBG and NGB lines after the red light-to-dark transition. Surprisingly, after the transition from 10 mmol m 22 s 21 red light to darkness, PBG inhibits hypocotyl elongation three times longer than NGB. The disassembly of photobodies in PBG hypocotyl nuclei correlates tightly with the accumulation of the growth-promoting transcription factor PHYTOCHROME-INTERACTING FACTOR3 (PIF3). Destabilizing photobodies by either decreasing the light intensity or adding monochromatic far-red light treatment before the light-to-dark transition leads to faster PIF3 accumulation and a dramatic reduction in the capacity for hypocotyl growth inhibition in PBG. In contrast, NGB is defective in PIF3 degradation, and its hypocotyl growth in the dark is nearly unresponsive to changes in light conditions. Together, our results support the model that photobodies are required for the prolonged, light-dependent inhibition of hypocotyl elongation in the dark by repressing PIF3 accumulation and by stabilizing the far-red light-absorbing form of phyB. Our study suggests that photobody localization patterns of phyB could serve as instructive cues that control light-dependent photomorphogenetic responses in the dark.

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Dimers of the N-terminal domain of phytochrome B are functional in the nucleus

Cited by 286 publications

References 30 publications

A Constitutively Active Allele of Phytochrome B Maintains Circadian Robustness in the Absence of Light

A Constitutively Active Allele of Phytochrome B Maintains Circadian Robustness in the Absence of Light

Structure and Function of Animal Cryptochromes

Photobody Localization of Phytochrome B Is Tightly Correlated with Prolonged and Light-Dependent Inhibition of Hypocotyl Elongation in the Dark

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