Photocontrol of subcellular partitioning of phytochrome‐B:GFP fusion protein in tobacco seedlings

Gil, Patricia; Kircher, Stefan; Ádám, Éva; Bury, Erik; Kozma‐Bognár, László; Schäfer, Eberhard; Nagy, Ferenc

doi:10.1046/j.1365-313x.2000.00730.x

Cited by 70 publications

(64 citation statements)

References 41 publications

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“…1). Published studies (16,20) and our own results from the phyB mislocalization screen further corroborate this conclusion. Mutations in the phyB apoprotein do not form NBs in high-fluence rates of R. However, all these mutants retain some phyB function (Fig.…”

Section: Discussionsupporting

confidence: 81%

“…phyA nuclear import is fast and induced by either FR or R; in contrast, phyB nuclear import is relatively slow, is induced only in R, and can be reversed by FR. Nuclear import of phyB also depends on the fluence rate of R (13)(14)(15)(16). In the nucleus, phytochromes localize to discrete subnuclear foci (13)(14)(15)17), which appear similar to nuclear bodies (NBs) defined in other systems (18,19).…”

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confidence: 99%

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Characterization of the requirements for localization of phytochrome B to nuclear bodies

Meng

Schwab

Chory

2003

Proc. Natl. Acad. Sci. U.S.A.

160

213

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Phytochromes are red-and far-red-sensing photoreceptors that detect the quantity, quality, and duration of light throughout the entire life cycle of plants. Phytochromes accumulate in the cytoplasm in the dark. As one of the earliest responses after light illumination, phytochromes localize to the nucleus where they become associated with discrete nuclear bodies (NBs). Here, we describe the steady-state dynamics of Arabidopsis phytochrome B (phyB) localization in response to different light conditions and define four phyB subnuclear localization patterns: diffuse nuclear localization, small and numerous NBs only, both small and large NBs, and large NBs only. We show that phyB nuclear import is not sufficient for phyB NB formation. Rather, phyB accumulation in NBs is mainly determined by the percentage of the total amount of phyB protein that is in the active phyB conformer, with large NBs always correlating with strong phyB responses. A genetic screen to identify determinants required for subnuclear localization of phyB resulted in several phyB mutants, mutants deficient in phytochrome chromophore biosynthesis, and mutations in at least one previously uninvestigated locus. This study lays the groundwork for future investigations to identify the molecular mechanisms of light-regulated partitioning of plant photoreceptors to discrete subnuclear domains.

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Section: Discussionsupporting

confidence: 81%

mentioning

confidence: 99%

Characterization of the requirements for localization of phytochrome B to nuclear bodies

Meng

Schwab

Chory

2003

Proc. Natl. Acad. Sci. U.S.A.

160

213

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“…Interactions of red light-absorbing phytochrome and blue light-absorbing cryptochrome signaling cascades have been reported (Casal and Boccalandro, 1995;Ahmad and Cashmore, 1997;Hennig et al, 1999). Furthermore, nuclear import of phyB was initiated by blue light, but not by light of 695 nm, which establishes a similar phytochrome photoequilibrium as blue light (Gil et al, 2000). Finally, cryptochromes were found to be required for phytochrome signaling to the circadian clock .…”

Section: Hypersensitivity Of Cry1-l407f To Various Light Qualities Rementioning

confidence: 84%

A Gain-of-Function Mutation of Arabidopsis CRYPTOCHROME1 Promotes Flowering

et al. 2010

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Plants use different classes of photoreceptors to collect information about their light environment. Cryptochromes are blue light photoreceptors that control deetiolation, entrain the circadian clock, and are involved in flowering time control. Here, we describe the cry1-L407F allele of Arabidopsis (Arabidopsis thaliana), which encodes a hypersensitive cryptochrome1 (cry1) protein. Plants carrying the cry1-L407F point mutation have elevated expression of CONSTANS and FLOWERING LOCUS T under short-day conditions, leading to very early flowering. These results demonstrate that not only the well-studied cry2, with an unequivocal role in flowering promotion, but also cry1 can function as an activator of the floral transition. The cry1-L407F mutants are also hypersensitive toward blue, red, and far-red light in hypocotyl growth inhibition. In addition, cry1-L407F seeds are hypersensitive to germination-inducing red light pulses, but the far-red reversibility of this response is not compromised. This demonstrates that the cry1-L407F photoreceptor can increase the sensitivity of phytochrome signaling cascades. Molecular dynamics simulation of wild-type and mutant cry1 proteins indicated that the L407F mutation considerably reduces the structural flexibility of two solvent-exposed regions of the protein, suggesting that the hypersensitivity might result from a reduced entropic penalty of binding events during downstream signal transduction. Other nonmutually exclusive potential reasons for the cry1-L407F gain of function are the location of phenylalanine-407 close to three conserved tryptophans, which could change cry1's photochemical properties, and stabilization of ATP binding, which could extend the lifetime of the signaling state of cry1.Light determines the plant's life, because light is the essential energy source for plant metabolism. The spatial, temporal, and spectral variability of light provides cues about the time of day, the season, and the presence of competitors for light. Sensitive and precise light perception, therefore, is essential to properly adjust plant development for maximal photosynthetic efficiency, to correlate vegetative and reproductive growth with favorable seasons, and eventually to maximize fitness. To cope with this task, plants have evolved several types of photoreceptors, including the phytochromes and cryptochromes (for review, see Banerjee and Batschauer, 2005;Josse et al., 2008;Mü ller and Carell, 2009). Phytochromes are red and far-red light receptors and regulate different aspects of plant development, such as hypocotyl elongation in red and far-red light and shade avoidance responses (Franklin et al., 2005). In addition, the two major phytochromes in Arabidopsis (Arabidopsis thaliana), phytochrome A (phyA) and phyB, are involved in flowering time control: phyA promotes flowering under short-day (SD) and long-day (LD) photoperiods (Johnson et al., 1994), while phyB acts as a floral inhibitor (Reed et al., 1993;Mockler et al., 1999).Cryptochromes are flavoproteins with two chromoph...

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“…In presence of light, the phyB-GFP fusion protein translocates into the nucleus and forms speckles in 2 h whereas phyA-GFP molecules are transported into the nucleus within 15 min in Arabidopsis, indicating that kinetics of nuclear localization and speckle formation vary with the type of phytochromes (Kircher et al, 1999;Kim et al, 2000). The nuclear accumulation and speckle formation of phyA-GFP were equally effective upon red, far-red and blue-light irradiation, whereas the phyB-GFP protein formed the speckles only under red-light (Gil et al, 2000;Kim et al, 2000). Phytochromes carrying missense mutations in the C-terminal PAS domain (and not in the HKRD domain) failed to form speckles inside the nucleus, indicating the importance of PAS domain region for speckle formation .…”

Section: Phytochromes and Nuclear Speckle Formationmentioning

confidence: 99%