Statoliths in Phycomyces : spectrofluorometric characterization of octahedral protein crystals

Fries, Volker; Krockert, Tanja; Grolig, Franz; Galland, Paul

doi:10.1078/0176-1617-00603

Cited by 11 publications

(11 citation statements)

References 24 publications

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“…The statoliths of P. blakesleeanus are identical with the previously described vacuolar protein crystals that display a paracrystalline structure (Ootaki and Wolken, 1973). The protein crystals are made up of of three proteins that contain noncovalently bound pterin-and flavin-like pigments Fries et al, 2002). Stage-1 sporangiophores (without sporangium) possess an apical aggregate of large lipid globules, which migrate in the subsequent developmental stages 2 to 4 into the columella (the central part of the sporangium, which does not contain spores).…”

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confidence: 50%

Optospectroscopic Detection of Primary Reactions Associated with the Graviperception of Phycomyces. Effects of Micro- and Hypergravity

Schmidt

Galland

2004

Plant Physiology

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The graviperception of sporangiophores of the fungus Phycomyces blakesleeanus involves gravity-induced absorbance changes (GIACs) that represent primary responses of gravitropism (Schmidt and Galland, 2000). GIACs (ΔA460–665) of sporangiophores were measured in vivo with a micro-dual wavelength spectrometer at 460 and 665 nm. Sporangiophores that were placed horizontally displayed an instant increase of the GIACs while the return to the vertical position elicited an instant decrease. The GIACs are specific for graviperception, because they were absent in a gravitropism mutant with a defective madJ gene. During parabola flights hypergravity (1.8g) elicited a decrease of the GIACs, while microgravity (0 ± 3 × 10−2 g) elicited an instant increase. Hypergravity that was generated in a centrifuge (1.5–6.5g) elicited also a decrease of the GIACs that saturated at about 5g. The GIACs have a latency of about 20 ms or shorter and are thus the fastest graviresponses ever measured for fungi, protists, and plants. The threshold for eliciting the GIACs is near 3 × 10−2 g, which coincides numerically with the threshold for gravitropic bending. In contrast to gravitropic bending, which requires long-term stimulation, GIACs can be elicited by stimuli as short as 20 to 100 ms, leading to an extremely low threshold dose (acceleration × time) of about 3 × 10−3 g s, a value, which is four orders of magnitude below the ones described for other organisms and which makes the GIACs of Phycomyces blakesleeanus the most sensitive gravi-response in literature.

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confidence: 50%

Optospectroscopic Detection of Primary Reactions Associated with the Graviperception of Phycomyces. Effects of Micro- and Hypergravity

Schmidt

Galland

2004

Plant Physiology

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“…The maximum of the excitation spectrum at 345 nm is compatible with a pterin-like pigment or even with NAD(P)H 2 ; the minor maxima at 390/415 and 470 nm resemble those of flavins. Aqueous mixtures of monapterin and riboflavin that contain the two pigments in ratios of about 6:1 resemble rather closely the in vivo fluorescence spectra of the sporangiophores (Fries et al 2002).…”

Section: Resultsmentioning

confidence: 98%

Light-induced fluorescence changes in Phycomyces : evidence for blue light-receptor associated flavo-semiquinones

Galland

Tölle

2003

Planta

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Light-induced fluorescence changes (LIFCs) were detected in sporangiophores of the blue-light-sensitive fungus Phycomyces blakesleeanus (Burgeff). The LIFCs can be utilized as a spectrophotometric assay for blue-light photoreceptors and for the in vivo characterization of their photochemical primary reactions. Blue-light irradiation of sporangiophores elicited a transient decrease and subsequent regeneration of flavin-like fluorescence emission at 525 nm. The signals recovered in darkness in about 120 min. In contrast to blue light, near-UV (370 nm) caused an increase in the fluorescence emission at 525 nm. Because the LIFCs were altered in a light-insensitive madC mutant with a defective photoreceptor, the fluorescence changes must be associated with early photochemical events of the transduction chain. Action spectra for the fluorescence changes at 525 nm showed major peaks near 470 and 600 nm. Double-pulse experiments involving two consecutive pulses of either blue and near-UV, blue and red, or near-UV and red showed that the responses depended on the sequence in which the different wavelengths were applied. The results indicate a blue-light receptor with intermediates in the near-UV, blue and red spectral regions. We explain the results in the framework of a general model, in which the three redox states of the flavin photoreceptor, the oxidized flavin (Fl), the flavo-semiquinone (FlH*), and the flavo-hydroquinone (FlH2) are each acting as chromophores with their own characteristic photochemical primary reactions. These consist of the photoreduction of the oxidized flavin generating semiquinone, the photoreduction of the semiquinone generating hydroquinone, and the photooxidation of the flavo-hydroquinone regenerating the pool of oxidized flavins. The proposed mechanism represents a photocycle in which two antagonistic photoreceptor forms, Fl and FlH2, determine the pool size of the biological effector molecule, the flavo-semiquinone. The redox changes that are associated with the photocycle are maintained by redox partners, pterins, that function in the near-UV as secondary chromophores.

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“…It is thus feasible that they contain in situ reduced or half-reduced flavins (FMN or FAD) and pterins which could bind to the tonoplast upon reorientation of the sporangiophore. Alternatively, they may interact with redox partners present in the tonoplast or, for example, with Ca 2+ (Fries et al, 2002). In this work we tested whether or not the crystals could be possibly involved in the sensitivity of gravitropism and growth toward Ca 2+ .…”

Section: Octahedral Protein Crystalsmentioning

confidence: 98%

“…The octahedral crystals contain three major proteins of relative molecular masses of 16, 46.5 and 55 kDa (Eibel et al, 2000). We had previously proposed that the crystals may not act primarily via exerting pressure on the vacuolar membrane (tonoplast), but rather by contact that allows ''chemical'' interaction with the membrane and the hypothetical gravireceptor (Eibel et al, 2000;Fries et al, 2002). Evidence for a gravisensing mechanism that relies on contact of statoliths with the gravireceptor rather than on pressure has been recently presented for the rhizoids of Chara (Limbach et al, 2005).…”

Section: Octahedral Protein Crystalsmentioning

confidence: 99%

Gravireception of the sporangiophore of Phycomyces blakesleeanus

Galland

Fries

Grolig

et al. 2007

Advances in Space Research

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Statoliths in Phycomyces : spectrofluorometric characterization of octahedral protein crystals

Cited by 11 publications

References 24 publications

Optospectroscopic Detection of Primary Reactions Associated with the Graviperception of Phycomyces. Effects of Micro- and Hypergravity

Optospectroscopic Detection of Primary Reactions Associated with the Graviperception of Phycomyces. Effects of Micro- and Hypergravity

Light-induced fluorescence changes in Phycomyces : evidence for blue light-receptor associated flavo-semiquinones

Gravireception of the sporangiophore of Phycomyces blakesleeanus

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