Ultrafast E to Z photoisomerization dynamics of the Cph1 phytochrome

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

Duanmu

Martin

et al. 2014

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163

180

Plant phytochromes are photoswitchable red/far-red photoreceptors that allow competition with neighboring plants for photosynthetically active red light. In aquatic environments, red and far-red light are rapidly attenuated with depth; therefore, photosynthetic species must use shorter wavelengths of light. Nevertheless, phytochrome-related proteins are found in recently sequenced genomes of many eukaryotic algae from aquatic environments. We examined the photosensory properties of seven phytochromes from diverse algae: four prasinophyte (green algal) species, the heterokont (brown algal) Ectocarpus siliculosus, and two glaucophyte species. We demonstrate that algal phytochromes are not limited to red and far-red responses. Instead, different algal phytochromes can sense orange, green, and even blue light. Characterization of these previously undescribed photosensors using CD spectroscopy supports a structurally heterogeneous chromophore in the far-red–absorbing photostate. Our study thus demonstrates that extensive spectral tuning of phytochromes has evolved in phylogenetically distinct lineages of aquatic photosynthetic eukaryotes.

Section: Discussioncontrasting

confidence: 41%

Eukaryotic algal phytochromes span the visible spectrum

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

Duanmu

Martin

et al. 2014

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163

180

“…The first was the cyanobacterial phytochrome Cph1 from Synechocystis sp. PCC 6803, a well‐characterized model protein for understanding phytochrome structure and function (Hughes et al ., ; Yeh et al ., ; Borucki et al ., ; Fischer & Lagarias, ; Fischer et al ., ; Strauss et al ., ; Hahn et al ., ; Rohmer et al ., ; Essen et al ., ; Rockwell et al ., ; Song et al ., ,b; Kim et al ., , , ,b). Cph1 exhibits considerable heterogeneity.…”

Section: Resultsmentioning

confidence: 99%

The phycocyanobilin chromophore of streptophyte algal phytochromes is synthesized by HY2

Martin

et al. 2017

New Phytologist

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Summary Land plant phytochromes perceive red and far-red light to control growth and development, using the linear tetrapyrrole (bilin) chromophore phytochromobilin (PΦB). Phytochromes from streptophyte algae, sister species to land plants, instead use phycocyanobilin (PCB). PCB and PΦB are synthesized by different ferredoxin-dependent bilin reductases (FDBRs): PΦB is synthesized by HY2, whereas PCB is synthesized by PcyA. The pathway for PCB biosynthesis in streptophyte algae is unknown. We used phylogenetic analysis and heterologous reconstitution of bilin biosynthesis to investigate bilin biosynthesis in streptophyte algae.Phylogenetic results suggest that PcyA is present in chlorophytes and prasinophytes but absent in streptophytes. A system reconstituting bilin biosynthesis in Escherichia coli was modified to utilize HY2 from the streptophyte alga Klebsormidium flaccidum (KflaHY2). The resulting bilin was incorporated into model cyanobacterial photoreceptors and into phytochrome from the early-diverging streptophyte alga Mesostigma viride (MvirPHY1).All photoreceptors tested incorporate PCB rather than PΦB, indicating that KflaHY2 is sufficient for PCB synthesis without any other algal protein. MvirPHY1 exhibits a red–far-red photocycle similar to those seen in other streptophyte algal phytochromes.These results demonstrate that streptophyte algae use HY2 to synthesize PCB, consistent with the hypothesis that PΦB synthesis arose late in HY2 evolution.

“…the multicomponent global analysis formalism that has been successfully applied to characterizing the photodynamics of other CBCR systems. 16,22,23,[26][27][28][35][36][37] The complete methodology of this approach is described elsewhere, 38 but the gist involves decomposing the transient data into a set of distinct populations with time-independent spectra and timedependent amplitudes. For the data discussed here, the constituent populations are assumed to evolve via activated barrier-crossing dynamics, which can be described by first-order kinetics:…”

Section: 34mentioning

confidence: 99%

“…Depending on the spectral properties of the incident light and the secondary dynamics (>10 ns) coupling these primary dynamics to the terminal 15,16,22,23,[25][26][27] the secondary dynamics (10 ns -10 ms) of CBCRs have attracted less attention, with only four so characterized: AnPixJg2 from Nostoc sp. strain PCC 7120, 29,30 Slr1393g3 from Synechocystis sp.…”

mentioning

confidence: 99%

“…In the primary (100 fs-10 ns) photodynamics of most phytochromes [17][18][19][20][21][22] and CBCRs [22][23][24][25][26][27][28] characterized to date, a single primary intermediate is typically resolved after the photoexcitation of the respective dark-adapted states. However, forward reaction photodynamics of RcaE are unique, with three primary intermediates observed after excitation of…”

mentioning

confidence: 99%

See 1 more Smart Citation

Tracking the secondary photodynamics of the green/red cyanobacteriochrome RcaE from Fremyella diplosiphon

Chang

Gottlieb

Chemical Physics Letters

et al. 2016

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(100 words)Cyanobacteriochrome RcaE regulates Type III complementary chromatic adaption in the cyanobacterium Fremyella diplosiphon by photoswitching between a green-absorbing dark state Meta-G o1 and Meta-G o2 intermediates, with a protonation reaction occurring at the final step on the millisecond timescale. Reverse reaction dynamics were characterized and reveal an unusually long-lived Lumi-R f photoproduct and a blue-shifted Meta-R y intermediate.