Photosynthesis of the Cyanidioschyzon merolae cells in blue, red, and white light

Kinga Kania,Tomasz Krupnik,Eugeniusz Parys,Elżbieta Romanowska,Ilona Kułak

doi:10.1007/s11120-020-00796-x

Abstract

Photosynthesis and respiration rates, pigment contents, CO2 compensation point, and carbonic anhydrase activity in Cyanidioschizon merolae cultivated in blue, red, and white light were measured. At the same light quality as during the growth, the photosynthesis of cells in blue light was significantly lowered, while under red light only slightly decreased as compared with white control. In white light, the quality of light during growth had no effect on the rate of photosynthesis at low O2 and high CO2 concentration, whereas their atmospheric level caused only slight decrease. Blue light reduced markedly photosynthesis rate of cells grown in white and red light, whereas the effect of red light was not so great. Only cells grown in the blue light showed increased respiration rate following the period of both the darkness and illumination. Cells grown in red light had the greatest amount of chlorophyll a, zeaxanthin, and β-carotene, while those in blue light had more phycocyanin. The dependence on O2 concentration of the CO2 compensation point and the rate of photosynthesis indicate that this alga possessed photorespiration. Differences in the rate of photosynthesis at different light qualities are discussed in relation to the content of pigments and transferred light energy together with the possible influence of related processes. Our data showed that blue and red light regulate photosynthesis in C. merolae for adjusting its metabolism to unfavorable for photosynthesis light conditions.

Highlights

Taxonomic position, classification, and physiology of Cyanidioschyzon merolaeThe Cyanidioschyzon merolae is a member of Cyanidiales, and order of red algae, it is a small (1.5 × 3.5 μm in size) thermo-acidophilic unicellular alga isolated from an Italian volcanic hot springs (Merola et al 1981)
We describe the findings of experiments with C. merolae cells which show that the photosynthetic activity depended on the light quality during growth and on its quality during photosynthesis
The CO2 uptake of C. merolae during photosynthesis (Pn) revealed that the pattern of CO2 fixation by the cells suspended in Allen medium and illuminated with white light (100 μmol photons m −2 s−1) was the same as that by the leaves of C3 plants in the atmosphere of air O2 (21% O 2) or low O 2 (i.e., 1–2%)

Summary

Introduction

The Cyanidioschyzon merolae is a member of Cyanidiales, and order of red algae, it is a small (1.5 × 3.5 μm in size) thermo-acidophilic unicellular alga isolated from an Italian volcanic hot springs (Merola et al 1981). It grows best at a pH of 1.5 and a temperature of 45 °C (Albertano et al 2000). The cell has an extremely simple structure, with one nucleus, one mitochondrion, and one chloroplast (Kuroiwa et al 1994). There is coordinated gene expression between the chloroplast and the mitochondrion, and the expressions of genes of both

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