Spectral Dependence of Photoregulation of Inorganic Nitrogen Metabolism in <i>Chlamydomonas reinhardii</i>

Azuara, María P.; Aparicio, Pedro J.

doi:10.1104/pp.77.1.95

Cited by 27 publications

(21 citation statements)

References 17 publications

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“…From these and previous results (3,14,15), it can be inferred that in green algae blue light is activating as many as three key steps oftheir inorganic nitrogen metabolism, namely (a) cell uptake of both nitrate and nitrite, (b) nitrate reductase activity, and (c) biosynthesis of nitrite reductase. In these photoregulatory processes, flavins might play an outstanding role as photosensitizers, although molybdopterins might also be involved (9).…”

Section: Resultssupporting

confidence: 60%

“…Con appears to be fully operative under any circumstance (10). While nitrate reductase is generally considered a cytosolic enzyme, nitrite reductase is probably located inside the chloroplast (8,17,21 (1,3). In Monoraphidium braunii, the action spectrum of this photoactivation showed two main bands (15), one in the blue with two peaks at 450 and 480 nm, and the other in the UVA region with a maximum at 365 nm.…”

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confidence: 99%

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Blue Light, a Positive Switch Signal for Nitrate and Nitrite Uptake by the Green Alga Monoraphidium braunii

Aparicio¹,

Quiñones²

1991

Plant Physiol.

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Section: Resultssupporting

confidence: 60%

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confidence: 99%

Blue Light, a Positive Switch Signal for Nitrate and Nitrite Uptake by the Green Alga Monoraphidium braunii

Aparicio¹,

Quiñones²

1991

Plant Physiol.

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“…Because nitrogen metabolism is similarly affected by blue light in Chlamydomonas and Chlorella (1,10), the observed blue light effects on cell division are obviously not mediated by effects on nitrogen metabolism.…”

Section: Discussionmentioning

confidence: 99%

“…There is evidence for the presence of phytochrome (19) and at least one blue light receptor (1,2,4,6,7,9,11,14,24) in Chlamydomonas. Our data clearly demonstrate that the light/dark control of cell division is not mediated by phytochrome but that the light-induced delay of cell division is a blue light effect.…”

Section: Discussionmentioning

confidence: 99%

Blue Light Regulation of Cell Division in Chlamydomonas reinhardtii

Münzner

Voigt²

1992

Plant Physiol.

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A delay in cell division was observed when synchronized cultures of the unicellular green alga Chiamydomonas reinhardtii growing under heterotrophic conditions were exposed to white light during the second half of the growth period. This effect was also observed when photosynthesis was blocked by addition of the photosystem 11 inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Light pulses of 10 minutes were sufficient to induce a delay in cell division in the presence or absence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. A delay in cell division was induced by blue light but not by illumination with red or far-red light. The equal intensity action spectrum revealed two peaks at 400 and 500 nm.Photoautotrophically growing cultures of unicellular green algae can be synchronized by alternating periods of light and darkness (18,20,23). In the case of Chlamydomonas reinhardtii, synchronization by light/dark cycling was also achieved in the presence of acetate (8,26), which is metabolized by this phytoflagellate. C reinhardtii cultures synchronized in the presence of acetate continue to divide synchronously for one cell cycle period when transferred to heterotrophic growth conditions (26). This finding enabled us to investigate the differential effects of light on cell growth and cell division. Illumination at the beginning of the growth period caused an increased growth rate. As a consequence, the cells entered the division phase earlier than dark-grown cells (26). However, when the cultures were exposed to light after the cells had doubled their mass, a considerable delay in cell division was observed, which was accompanied by an extended growth period (26). The light-induced delay in cell division was also observed in the presence of DCMU, an inhibitor of PSII.These observations indicate that the transition from cell growth to cell division is regulated by a light/dark-responsive cell cycle switch in C. reinhardtii (26) and that photosynthesis is apparently not involved in this process. Therefore, we have investigated which wavelengths and intensities of light are effective in inducing a delay in cell division. The aim of these 'Supported by a grant (Vo 327/1) from the Deutsche Forschungsgemeinschaft.

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“…), probably to avoid its toxic effects (Vennesland & Guerrero 1979). The most frequent cause of this imbalance is the Limitation of NH4+ fixation due to a n insufficient carbon skeleton production rate (Eisele & Ullrich 1977, Azuara & Aparicio 1985. The low concentration factor for NH,' may be interpreted as the result of a large turnover of internal NH,'.…”

Section: Internal and External Nitrate Nitrite And Ammonium Concentrmentioning

confidence: 99%

Seasonal cycle of the gametophytic form of Porphyra umbilicalis: nitrogen and carbon

Hernández¹,

Corzo²,

R³

et al. 1993

Mar. Ecol. Prog. Ser.

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Seasonal variations in environmental factors (irradiance, seawater concentration of NO,, NOp-and NH4+, temperature) and in physiological variables of Porphyra umbiljcalis (L.) Kiitzing (intracellular NOn-, NO2-and NH; concentrations, nitrate reductase activity, amino acids, soluble proteins, total C, total N, C:N:P ratio) were determined during winter 1991-92 at a site in Lagos (Malaga, southern coast of Spam). In the western Mediterranean Sea, the leafy thallus of P. urnbd~cahs occurs only during winter (mid-December to mid-March). Maximal % cover (80 %) was reached in the first part of February. Conditions of low temperature (14.7 _+ 0.6OC), short days (10 h daylight) and low global solar irradiance (2.5 to 3 4 kWh m-2) prevailed during the period of increase in ?/o cover. The period of decrease in % cover was characterized by long days (12 h), higher irradiance (3.4 to 5 kWh m-2), and slightly higher water temperature (15.5 f 1.34 "C). NO, concentration in seawater ([NO,],) at the study site ranged from 1 to 6.7 FM, [NOz-], was always lower than l pM, and [NH,'],, the largest source of inorganic nitrogen, ranged from 6.8 to 17.6 pM. Intracellular concentration of NO, ([NO,],) ranged from 2.8 to 51.3 mm01 1-' cell water (11.7 to 210.6 ymol g -' dry wt), which represents a concentration factor of up to 4.2 X 104 with respect to the seawater. [NO,-], ranged from 0.2 to 0.7 mm01 1-' cell water and [NH;], from 0.016 to 2.2 mm01 1-' cell water. Nitrate reductase (NR) activity varied widely during the winter cycle (between 1.2 and 9.4 pm01 NOp-g-' fresh wt h-'). It was found to be a very sensit.ive parameter for indicating when NOT is being used as the N source for growth. Therefore, low NR activity levels coincided with the highest [NO

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Spectral Dependence of Photoregulation of Inorganic Nitrogen Metabolism in Chlamydomonas reinhardii

Cited by 27 publications

References 17 publications

Blue Light, a Positive Switch Signal for Nitrate and Nitrite Uptake by the Green Alga Monoraphidium braunii

Blue Light, a Positive Switch Signal for Nitrate and Nitrite Uptake by the Green Alga Monoraphidium braunii

Blue Light Regulation of Cell Division in Chlamydomonas reinhardtii

Seasonal cycle of the gametophytic form of Porphyra umbilicalis: nitrogen and carbon

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