Blue Light Sensing and Signaling by the Phototropins

Christie, John M.; Briggs, Winslow R.

doi:10.1002/352760510x.ch13

Cited by 20 publications

(16 citation statements)

References 74 publications

(159 reference statements)

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“…Phototropins, the plant blue-light photoreceptors mediating phototropism, are the best photochemically and structurally studied LOV-domain-containing photoreceptors (Briggs and Huala 1999;Christie et al 1999;Crosson and Moffat 2001;Harper et al 2003;Christie and Briggs 2005). Like many other photoreceptors, phototropins undergo rapid photocycles in the dark after their light activation to return to the dark state (Salomon et al 2000), so that they can be repeatedly activated by light.…”

mentioning

confidence: 99%

Molecular mechanism of light responses in Neurospora: from light-induced transcription to photoadaptation

He¹,

Liu²

2005

Genes Dev.

193

239

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mentioning

confidence: 99%

Molecular mechanism of light responses in Neurospora: from light-induced transcription to photoadaptation

He¹,

Liu²

2005

Genes Dev.

193

239

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“…The past decade has witnessed the discovery of a large number of novel flavin-binding photoreceptors, notably the phototropins, the cryptochromes, and BLUF (blue-light sensing using FAD) domains (1). Phototropins are primarily found in plants and control several physiological responses such as phototropism, chloroplast movement, and stomatal opening (2), whereas cryptochromes are known to regulate growth and development in plants and circadian rhythms in plants and insects (3,4). BLUF domains are a distinct family of flavin-binding photoreceptors that show no significant relationship to other sensor proteins in sequence or structure.…”

mentioning

confidence: 99%

Hydrogen-bond switching through a radical pair mechanism in a flavin-binding photoreceptor

Gauden

Stokkum²,

Key³

et al. 2006

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

216

435

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BLUF (blue light sensing using FAD) domains constitute a recently discovered class of photoreceptor proteins found in bacteria and eukaryotic algae, where they control a range of physiological responses including photosynthesis gene expression, photophobia, and negative phototaxis. Other than in well known photoreceptors such as the rhodopsins and phytochromes, BLUF domains are sensitive to light through an oxidized flavin rather than an isomerizable cofactor. To understand the physicochemical basis of BLUF domain photoactivation, we have applied femtosecond transient absorption spectroscopy to the Slr1694 BLUF domain of Synechocystis PCC6803. We show that photoactivation of BLUF domains proceeds by means of a radical-pair mechanism, driven by electron and proton transfer from the protein to the flavin, resulting in the transient formation of anionic and neutral flavin radical species that finally result in the long-lived signaling state on a 100-ps timescale. A pronounced deuteration effect is observed on the lifetimes of the intermediate radical species, indicating that proton movements underlie their molecular transformations. We propose a photoactivation mechanism that involves a successive rupture of hydrogen bonds between a conserved tyrosine and glutamine by light-induced electron transfer from tyrosine to flavin and between the glutamine and flavin by subsequent protonation at flavin N5. These events allow a reorientation of the conserved glutamine, resulting in a switching of the hydrogen-bond network connecting the chromophore to the protein, followed by radicalpair recombination, which locks the glutamine in place. It is suggested that the redox potential of flavin generally defines the light sensitivity of flavin-binding photoreceptors.flavoprotein ͉ light sensing ͉ photochemistry ͉ reaction mechanism ͉ spectroscopy

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“…Plants are known to contain three classes of bluelight-specific receptors: the cryptochromes (Batschauer, 2005), the phototropins (Celaya and Liscum, 2005;Christie and Briggs, 2005), and FKF1 (flavin-binding, kelch repeat, F-box; Imaizumi et al, 2003), a member of the ZEITLUPE/ADAGIO putative family of photoreceptors (Schultz, 2005). Among these photoreceptors, the phototropins are known to mediate phototropism, chloroplast movements, stomatal opening, leaf expansion, and the rapid inhibition of growth of etiolated hypocotyls (Christie and Briggs, 2005).…”

mentioning

confidence: 99%

“…Among these photoreceptors, the phototropins are known to mediate phototropism, chloroplast movements, stomatal opening, leaf expansion, and the rapid inhibition of growth of etiolated hypocotyls (Christie and Briggs, 2005).…”

mentioning

confidence: 99%

Physiological Roles of the Light, Oxygen, or Voltage Domains of Phototropin 1 and Phototropin 2 in Arabidopsis

et al. 2006

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(E.K., S.S., J.M.C.)Phototropins (phot1 and phot2) are plant blue-light receptors that mediate phototropism, chloroplast movement, stomatal opening, rapid inhibition of growth of etiolated seedlings, and leaf expansion in Arabidopsis (Arabidopsis thaliana). Their N-terminal region contains two light, oxygen, or voltage (LOV) domains, which bind flavin mononucleotide and form a covalent adduct between a conserved cysteine and the flavin mononucleotide chromophore upon photoexcitation. The C-terminal region contains a serine/threonine kinase domain that catalyzes blue-light-activated autophosphorylation. Here, we have transformed the phot1 phot2 (phot1-5 phot2-1) double mutant with PHOT expression constructs driven by the cauliflower mosaic virus 35S promoter. These constructs encode either wild-type phototropin or phototropin with one or both LOV-domain cysteines mutated to block their photochemistry. We selected multiple lines in each of the eight resulting categories of transformants for further physiological analyses. Specifically, we investigated whether LOV1 and LOV2 serve the same or different functions for phototropism and leaf expansion. Our results show that the LOV2 domain of phot1 plays a major role in phototropism and leaf expansion, as does the LOV2 domain of phot2. No complementation of phototropism or leaf expansion was observed for the LOV1 domain of phot1. However, phot2 LOV1 was unexpectedly found to complement phototropism to a considerable level. Similarly, transformants carrying a PHOT transgene with both LOV domains inactivated developed strong curvatures toward high fluence rate blue light. However, we found that the phot2-1 mutant is leaky and produces a small level of full-length phot2 protein. In vitro experiments indicate that cross phosphorylation can occur between functional phot2 and inactivated phot1 molecules. Such a mechanism may occur in vivo and therefore account for the functional activities observed in the PHOT transgenics with both lov domains inactivated. The implications of this mechanism with respect to phototropin function are discussed.

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Blue Light Sensing and Signaling by the Phototropins

Cited by 20 publications

References 74 publications

Molecular mechanism of light responses in Neurospora: from light-induced transcription to photoadaptation

Molecular mechanism of light responses in Neurospora: from light-induced transcription to photoadaptation

Hydrogen-bond switching through a radical pair mechanism in a flavin-binding photoreceptor

Physiological Roles of the Light, Oxygen, or Voltage Domains of Phototropin 1 and Phototropin 2 in Arabidopsis

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