Ultraviolet radiation stimulated activity of extracellular carbonic anhydrase in the marine diatom Skeletonema costatum

2009 ◽  
Vol 36 (2) ◽  
pp. 137 ◽  
Author(s):  
Hongyan Wu ◽  
Kunshan Gao
Keyword(s):  
Carbonic Anhydrase ◽  
Ultraviolet Radiation ◽  
Uv Radiation ◽  
Carbon Fixation ◽  
Skeletonema Costatum ◽  
Marine Phytoplankton ◽  
Marine Diatom ◽  
Redox Activity ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon

Previous studies have shown that reduced levels of solar UV radiation (280–400 nm) can enhance photosynthetic carbon fixation of marine phytoplankton, but the mechanisms are not known. The supply of CO2 for photosynthesis is facilitated by extracellular (periplasmic) carbonic anhydrase (CAe) in most marine phytoplankton species. The present study showed that the CAe activity of Skeletonema costatum (Greville) Cleve was stimulated when treated with UV-A (320–395 nm) or UV-A + UV-B (295–320 nm) in addition to visible radiation. The presence of UV-A and UV-B enhanced the activity by 28% and 24%, respectively, at a low irradiance (PAR 161, UV-A 28, UV-B 0.9 W m−2) and by 21% and 19%, respectively, at a high irradiance (PAR 328, UV-A 58, UV-B 1.9 W m−2) level after exposure for 1 h. Ultraviolet radiation stimulated CAe activity contributed up to 6% of the photosynthetic carbon fixation as a result of the enhanced supply of CO2, as revealed using the CAe inhibitor (acetazolamide). As a result, there was less inhibition of photosynthetic carbon fixation compared with the apparent quantum yield of PSII. The UV radiation stimulated CAe activity coincided with the enhanced redox activity at the plasma membrane in the presence of UV-A and/or UV-B. The present study showed that UV radiation can enhance CAe activity, which plays an important role in counteracting UV inhibition of photosynthesis.

scholarly journals Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation

2017 ◽  
Author(s):  
Shanying Tong ◽  
David A. Hutchins ◽  
Kunshan Gao
Keyword(s):  
Ocean Acidification ◽  
Uv Radiation ◽  
Carbon Fixation ◽  
Co2 Concentration ◽  
Emiliania Huxleyi ◽  
Marine Phytoplankton ◽  
Negative Effects ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon ◽  
Increasing Temperature

Abstract. Marine phytoplankton such as bloom-forming, calcite-producing coccolithophores, are naturally exposed to solar UV radiation (UVR, 280–400 nm) in the ocean's upper mixed layers. Nevertheless, effects of increasing CO2-induced ocean acidification and warming have rarely been investigated in the presence of UVR. We examined calcification and photosynthetic carbon fixation performance in the most cosmopolitan coccolithophorid, Emiliania huxleyi, grown under high (1000 μatm, HC; pHT: 7.70) and low (400 μatm, LC; pHT: 8.02) CO2 levels, at 15 °C (LT), 20 °C (MT) and 24 °C (HT) with or without UVR. The HC treatment didn't affect photosynthetic carbon fixation at 15 °C, but significantly enhanced it with increasing temperature. Exposure to UVR inhibited photosynthesis, with higher inhibition by UVA (320–395 nm) than UVB (295–320 nm), except in the HC and 24 °C-grown cells, in which UVB caused more inhibition than UVA. Reduced thickness of the coccolith layer in the HC-grown cells appeared to be responsible for the UV-induced inhibition, and an increased repair rate of UVA-derived damage in the HCHT-grown cells could be responsible for lowered UVA-induced inhibition. While calcification was reduced with the elevated CO2 concentration, exposure to UVB or UVA affected it differentially, with the former inhibiting and the latter enhancing it. UVA-induced stimulation of calcification was higher in the HC-grown cells at 15 and 20 °C, whereas at 24 °C, observed enhancement was not significant. The calcification to photosynthesis ratio (Cal / Pho ratio) was lower in the HC treatment, and increasing temperature also lowered the value. However, at 20 and 24 °C, exposures to UVR significantly increased the Cal / Pho ratio, especially in HC-grown cells, by up to 100 %. This implies that UVR can counteract the negative effects of the greenhouse treatment on the Cal / Pho ratio, and so may be a key stressor when considering the impacts of future greenhouse conditions on E. huxleyi.

scholarly journals Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation

2019 ◽  
Vol 16 (2) ◽  
pp. 561-572 ◽  
Author(s):  
Shanying Tong ◽  
David A. Hutchins ◽  
Kunshan Gao
Keyword(s):  
Ocean Acidification ◽  
Carbon Fixation ◽  
Co2 Concentration ◽  
Emiliania Huxleyi ◽  
Marine Phytoplankton ◽  
Negative Effects ◽  
Solar Ultraviolet Radiation ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon ◽  
Increasing Temperature

Abstract. Marine phytoplankton such as bloom-forming, calcite-producing coccolithophores, are naturally exposed to solar ultraviolet radiation (UVR, 280–400 nm) in the ocean's upper mixed layers. Nevertheless, the effects of increasing carbon dioxide (CO2)-induced ocean acidification and warming have rarely been investigated in the presence of UVR. We examined calcification and photosynthetic carbon fixation performance in the most cosmopolitan coccolithophorid, Emiliania huxleyi, grown under high (1000 µatm, HC; pHT: 7.70) and low (400 µatm, LC; pHT: 8.02) CO2 levels, at 15 ∘C, 20 ∘C and 24 ∘C with or without UVR. The HC treatment did not affect photosynthetic carbon fixation at 15 ∘C, but significantly enhanced it with increasing temperature. Exposure to UVR inhibited photosynthesis, with higher inhibition by UVA (320–395 nm) than UVB (295–320 nm), except in the HC and 24 ∘C-grown cells, in which UVB caused more inhibition than UVA. A reduced thickness of the coccolith layer in the HC-grown cells appeared to be responsible for the UV-induced inhibition, and an increased repair rate of UVA-derived damage in the HC–high-temperature grown cells could be responsible for lowered UVA-induced inhibition. While calcification was reduced with elevated CO2 concentration, exposure to UVB or UVA affected the process differentially, with the former inhibiting it and the latter enhancing it. UVA-induced stimulation of calcification was higher in the HC-grown cells at 15 and 20 ∘C, whereas at 24 ∘C observed enhancement was not significant. The calcification to photosynthesis ratio (Cal ∕ Pho ratio) was lower in the HC treatment, and increasing temperature also lowered the value. However, at 20 and 24 ∘C, exposure to UVR significantly increased the Cal ∕ Pho ratio, especially in HC-grown cells, by up to 100 %. This implies that UVR can counteract the negative effects of the “greenhouse” treatment on the Cal ∕ Pho ratio; hence, UVR may be a key stressor when considering the impacts of future greenhouse conditions on E. huxleyi.

scholarly journals Ultraviolet Radiation Stimulates Activity of CO2 Concentrating Mechanisms in a Bloom-Forming Diatom Under Reduced CO2 Availability

2021 ◽  
Vol 12 ◽  
Author(s):  
Guang Gao ◽  
Wei Liu ◽  
Xin Zhao ◽  
Kunshan Gao
Keyword(s):  
Carbon Dioxide ◽  
Coastal Waters ◽  
Algal Blooms ◽  
Carbon Fixation ◽  
Skeletonema Costatum ◽  
Active Radiation ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon ◽  
Solar Uv ◽  
Co2 Concentrating Mechanisms

The diatom Skeletonema costatum is cosmopolitan and forms algal blooms in coastal waters, being exposed to varying levels of solar UV radiation (UVR) and reduced levels of carbon dioxide (CO2). While reduced CO2 availability is known to enhance CO2 concentrating mechanisms (CCMs) in this diatom and others, little is known on the effects of UV on microalgal CCMs, especially when CO2 levels fluctuate in coastal waters. Here, we show that S. costatum upregulated its CCMs in response to UVR (295–395 nm), especially to UVA (320–395 nm) in the presence and absence of photosynthetically active radiation (PAR). The intensity rise of UVA and/or UVR alone resulted in an increase of the activity of extracellular carbonic anhydrase (CAe); and the addition of UVA enhanced the activity of CCMs-related CAe by 23–27% when PAR levels were low. Such UV-stimulated CCMs activity was only significant at the reduced CO2 level (3.4 μmol L−1). In addition, UVA alone drove active HCO3− uptake although it was not as obvious as CAe activity, another evidence for its role in enhancing CCMs activity. In parallel, the addition of UVA enhanced photosynthetic carbon fixation only at the lower CO2 level compared to PAR alone. In the absence of PAR, carbon fixation increased linearly with increased intensities of UVA or UVR regardless of the CO2 levels. These findings imply that during S. costatum blooming period when CO2 and PAR availability becomes lower, solar UVR (mainly UVA) helps to upregulate its CCMs and thus carbon fixation, enabling its success of frequent algal blooms.

Sectioned rubisco crystals in TEM

1990 ◽  
Vol 48 (3) ◽  
pp. 664-665
Author(s):  
Gunnel Karlsson ◽  
Jan-Olov Bovin ◽  
Michael Bosma
Keyword(s):  
Plant Cell ◽  
Carbon Fixation ◽  
Unit Cell ◽  
Protein Crystals ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon

RuBisCO (D-ribulose-l,5-biphosphate carboxylase/oxygenase) is the most aboundant enzyme in the plant cell and it catalyses the key carboxylation reaction of photosynthetic carbon fixation, but also the competing oxygenase reaction of photorespiation. In vitro crystallized RuBisCO has been studied earlier but this investigation concerns in vivo existance of RuBisCO crystals in anthers and leaves ofsugarbeets. For the identification of in vivo protein crystals it is important to be able to determinethe unit cell of cytochemically identified crystals in the same image. In order to obtain the best combination of optimal contrast and resolution we have studied different staining and electron accelerating voltages. It is known that embedding and sectioning can cause deformation and obscure the unit cell parameters.

SYSTEMATICS OF PHOTOSYNTHETIC CARBON FIXATION PATHWAYS IN EUPHORBIA

Taxon ◽  
1975 ◽  
Vol 24 (1) ◽  
pp. 27-33 ◽  
Author(s):  
Grady L. Webster ◽  
Walter V. Brown ◽  
Bruce N. Smith
Keyword(s):  
Carbon Fixation ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon
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