Physiological bluelight reception

Schmidt, Werner

doi:10.1007/3-540-09958-1_1

Cited by 46 publications

(28 citation statements)

References 146 publications

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“…In one set of experiments, a fluence of 1 jMmolmM2 sec-1 saturated the pulse-induced response and a 100-sec pulse (equivalent to two consecutive 50-sec pulses) did not cause any detectable further increases in conductance. However, if sufficient time elapsed between two pulses, an increase in the total area below the conductance curve became apparent.…”

Section: Methodsmentioning

confidence: 91%

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Kinetic properties of the blue-light response of stomata

Iino

Ogawa

Zeiger

1985

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

113

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The stomatal response to blue light was analyzed with gas-exchange techniques in Commelina communis L. leaves by using high-fluence-rate short pulses. Pulses of blue light were given under a background of high-fluencerate red light, which maintained photosynthesis at near saturation and stomatal conductance at a steady state. A single blue light pulse of 1-100 sec induced an increase in stomatal conductance, which peaked after 15 min and then returned to the initial steady-state level within 50-60 min after the pulse. The response could be repeatedly induced in the same leaf. Red light pulses on a red background did not induce any comparable response. The stomatal response quantified by integrating the conductance increases after pulse application approached saturation with increasing pulse duration (t l2 =9 sec with 250 smol-m-2.sec' of blue light). After a saturating pulse, sensitivity to a second pulse was restored slowly. This recovery response, quantified from the conductance increases caused by the two pulses, approached saturation with a t 1/2 of W9 min. These results were used to test a model in which a molecular component in the sensory transduction process is considered to exist in two interconvertible forms, A and B. If B is the physiologically active form inducing stomatal opening, then A is the inactive form. The A to B conversion is a light-induced reaction and the B to A conversion is a thermal reaction. Rate constants for these reactions were estimated from single-and double-pulse experiments (at a fluence rate of 250Lmo'm-2-sec-1, k, = 0.075 sec'1; thermal rate constant kd = 0.0014 sec'1), allowing the calculation of steady-state concentration of B under continuous irradiation. (9). These properties provide a basis for the quantitative analyses of the early sensory reactions by measuring stomatal movement.Many of the BL responses can be induced by a short pulse of BL (10-13). In previous work with stomata, a rapid transient increase in transpiration in Avena leaves caused by a BL pulse as short as 3 sec has been reported (14). In the present study, we have characterized kinetic properties ofthe stomatal response to BL by using pulse stimulation. The responses were quantified in attached leaves of Commelina communis by using gas-exchange techniques. Background irradiation with high-fluence-rate red light (RL) was used to saturate and thereby minimized the component of the stomatal response to BL depending on photosynthesis in guard cells and the underlying mesophyll cells. The obtained results allowed us to test a kinetic model, which predicted the steady-state values of stomatal conductance under continuous BL. MATERIALS AND METHODSPlants of C. communis were grown from seed in pots of soil (Goldstrike potting soil, Master Nurserymen's Assoc., Concord, CA) in a greenhouse. Plants were watered daily, fertilized weekly with a solution of Spoonit (Plantsmith, Mountain View, CA) at ==3 g/liter, and used for experimentation when 4-6 weeks old.Stomatal conductance to water vapor and rates of C...

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Section: Methodsmentioning

confidence: 91%

“…It is currently thought that flavins are the photosensing pigments in many of the BL-sensitive responses (1,2). The precise nature of the photoreceptor and the primary photoreactions, however, remain unknown.…”

mentioning

confidence: 99%

Kinetic properties of the blue-light response of stomata

Iino

Ogawa

Zeiger

1985

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

113

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“…Carotenoids and other pigments cannot, however, be ruled out. Also, there might well be a variety of receptors triggering different responses in different organisms (2,6,(19)(20)(21)(22)(23). The action spectra of blue-light photoresponses can be approximated by flavin absorption spectra, provided one assumes that the molecular environment of the chromophore alters its energy levels enough to account for the fine structure of the peaks.…”

Section: Introductionmentioning

confidence: 99%

Elevated Riboflavin Requirement for Postphotoinductive Events in Sporulation of a Trichoderma Auxotroph

Horwitz

Gressel²

1983

Plant Physiol.

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A riboflavin auxotroph of Trichoderma required more riboflavin for bluelight-induced conidiation than for growth. Colonies transferred after Mumination from 0.2 micromolar (limiting conidiation, not growth) to 3.5 micromolar riboflavin (nonlimiting), responded the same as those grown at 3.5 micromolar. The additional riboflavin is therefore not required as a photoreceptor. The data do not rule out the hypothesis that cryptochrome(s) is/are flavin(s).A flavin or flavoprotein is a favorite candidate for the elusive blue-light photoreceptor 'cryptochrome.' Carotenoids and other pigments cannot, however, be ruled out. Also, there might well be a variety of receptors triggering different responses in different organisms (2,6,(19)(20)(21)(22)(23). The action spectra of blue-light photoresponses can be approximated by flavin absorption spectra, provided one assumes that the molecular environment of the chromophore alters its energy levels enough to account for the fine structure of the peaks. Indirect evidence for a flavin chromophore is accumulating. Delbriick et al. (3) found, in Phycomyces, a minor action spectrum peak at 600 nm that they attributed to direct excitation of the flavin triplet state. Loser and Schafer (14) suggest that at least two distinct absorbing species (perhaps a photochromic pigment) are involved in Phycomyces. A shift in the Phycomyces phototropic action spectrum was caused by culturing in the presence of roseoflavin, a riboflavin analog with longer wavelength absorption bands (17). Although this result certainly fits the idea of a flavin photoreceptor, roseoflavin may have acted as an artificial photosensitizer, as do redox dyes such as methylene blue (12).Isolation of mutants specifically defective in photoreceptor would provide an additional tool for identifying cryptochrome(s). This approach is being applied to Phycomyces phototropism (1, 13), to blue light responses of Neurospora (10, 18), and to photoinduced conidiation in Trichoderma (Horwitz, Malkin, Gressel, unpublished). If the chromophore is a flavin, however, a mutation causing complete lack of photoreceptor would be lethal. One way to circumvent this problem partially is to work with a riboflavin-E

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“…The analogs 1-deazariboflavin and roseoflavin, which have red-shifted absorption, acted as photoreceptors for the photosuppression and phase shifting of circadian conidiation by 540 nm Hght, but were ineffective as photoreceptors for the induction of carotenoid synthesis. These results provide additional evidence impUcating a flavin photoreceptor for at least two blue Ught responses of Newrospora.In a number of organisms, blue light responses appear to be mediated by a flavin or flavoprotein photoreceptor (22,23). For the fungus Neurospora crassa, spectrophotometric studies have implicated a flavin-mediated photoreduction of a b-type Cyt in such responses (3,14).…”

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confidence: 99%

Modification of Blue Light Photoresponses by Riboflavin Analogs in Neurospora crassa

Paietta

Sargent²

1983

Plant Physiol.

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The effect of riboflavin analogs on blue Ught responses in a riboflavin mutant of Neurospora crassa was studied. The analogs 1-deazariboflavin and roseoflavin, which have red-shifted absorption, acted as photoreceptors for the photosuppression and phase shifting of circadian conidiation by 540 nm Hght, but were ineffective as photoreceptors for the induction of carotenoid synthesis. These results provide additional evidence impUcating a flavin photoreceptor for at least two blue Ught responses of Newrospora.In a number of organisms, blue light responses appear to be mediated by a flavin or flavoprotein photoreceptor (22,23). For the fungus Neurospora crassa, spectrophotometric studies have implicated a flavin-mediated photoreduction of a b-type Cyt in such responses (3,14). Recent studies with mutant strains of Neurospora have also indicated flavin-Cyt b involvement because a Cyt b (2, 4) or flavin (17, 18) deficiency correlates with a decreased sensitivity to light. The specific flavoprotein(s) involved has not yet been identified, but it does not appear to be nitrate reductase (19), which has been suggested as a potential blue light receptor for Neurospora (12).Another approach that has proven useful in photobiology is the replacement of natural chromophores by analogs. Examples include the use of retinal analogs in the study of Halobacterium membranes (25) and mammalian vision (6). Only a few studies, however, have utilized analogs in the study of blue light responses. Page (16) used L-lyxoflavin, a riboflavin analog, in studies which indicated a flavin photoreceptor for trophocyst formation in Pilobolus. Two recent studies have applied this approach using roseoflavin, a riboflavin analog with red-shifted absorption. In Phycomyces, roseoflavin acted as a photoreceptor for phototropism (15), while in Neurospora it was ineffective as a photoreceptor for carotenogenesis (24).The present work examines the effect of riboflavin analogs on three Neurospora blue light responses: the suppression and phase shifting of circadian conidiation, and the induction of carotenoid synthesis. Two analogs, 1-deazariboflavin and roseoflavin, which have red-shifted absorption (26) as compared to riboflavin (535, 505, and 445 nm absorption maxima, respectively) were chosen for study following preliminary experiments with 17 different analogs. Neurospora will not normally respond to wavelengths above 520 nm for the three photoresponses described above (8,9,21). A response, therefore, of an analog-supplemented culture to longer wavelengths of light (e.g. 540 nm) can be unambiguously interpreted to have been potentiated by the analog.'Present address:

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Physiological bluelight reception

Cited by 46 publications

References 146 publications

Kinetic properties of the blue-light response of stomata

Kinetic properties of the blue-light response of stomata

Elevated Riboflavin Requirement for Postphotoinductive Events in Sporulation of a Trichoderma Auxotroph

Modification of Blue Light Photoresponses by Riboflavin Analogs in Neurospora crassa

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