TY - JOUR
T1 - Changes in Phenolic Compounds and Cellular Ultrastructure of Arctic and Antarctic Strains of Zygnema (Zygnematophyceae, Streptophyta) after Exposure to Experimentally Enhanced UV to PAR Ratio
AU - Pichrtová, Martina
AU - Remias, Daniel
AU - Lewis, Louise A.
AU - Holzinger, Andreas
N1 - Funding Information:
We thank Prof. Ursula Lütz-Meindl, University of Salzburg, Austria, for access to her high-pressure freezing device and Mag. Ancuela Andosch for the technical help in the high-pressure and freeze substitution process. Then, we would like to thank MSc. Siegfried Aigner, University of Innsbruck, and Shelley Olm, University of Connecticut, for the technical assistance. Prof. Jeffrey G. Duckett and Dr. Silvia Pressel, Natural History Museum, London, are acknowledged for helpful discussions. We also thank Dr. Tomáš Hájek, Academy of Sciences of the Czech Republic, for his advice on statistical analyses and valuable comments that improved the manuscript. The study was conducted during a research stay of M.P. at the University of Innsbruck funded by Österreichischer Austauschdienst scholarship (program AKTION). Support was granted as a long-term research development project of the Academy of Sciences of the Czech Republic RVO 67985939. The study was supported by the Tyrolean Science Fund (Project AP 717029) and the Austrian Science Fund (FWF—Project 24242) to A.H. and in part by the USA National Aeronautics and Space Administration (NASA) Exobiology NNX08AX20G grant to L.A.L.
PY - 2013/1
Y1 - 2013/1
N2 - Ultraviolet (UV) radiation has become an important stress factor in polar regions due to anthropogenically induced ozone depletion. Although extensive research has been conducted on adaptations of polar organisms to this stress factor, few studies have focused on semi-terrestrial algae so far, in spite of their apparent vulnerability. This study investigates the effect of UV on two semi-terrestrial arctic strains (B, G) and one Antarctic strain (E) of the green alga Zygnema, isolated from Arctic and Antarctic habitats. Isolates of Zygnema were exposed to experimentally enhanced UV A and B (predominant UV A) to photosynthetic active radiation (PAR) ratio. The pigment content, photosynthetic performance and ultrastructure were studied by means of high-performance liquid chromatography (HPLC), chlorophyll a fluorescence and transmission electron microscopy (TEM). In addition, phylogenetic relationships of the investigated strains were characterised using rbcL sequences, which determined that the Antarctic isolate (E) and one of the Arctic isolates (B) were closely related, while G is a distinct lineage. The production of protective phenolic compounds was confirmed in all of the tested strains by HPLC analysis for both controls and UV-exposed samples. Moreover, in strain E, the content of phenolics increased significantly (p = 0.001) after UV treatment. Simultaneously, the maximum quantum yield of photosystem II photochemistry significantly decreased in UV-exposed strains E and G (p < 0.001), showing a clear stress response. The phenolics were most probably stored at the cell periphery in vacuoles and cytoplasmic bodies that appear as electron-dense particles when observed by TEM after high-pressure freeze fixation. While two strains reacted moderately on UV exposure in their ultrastructure, in strain G, damage was found in chloroplasts and mitochondria. Plastidal pigments and xanthophyll cycle pigments were investigated by HPLC analysis; UV A- and UV B-exposed samples had a higher deepoxidation state as controls, particularly evident in strain B. The results indicate that phenolics are involved in UV protection of Zygnema and also revealed different responses to UV stress across the three strains, suggesting that other protection mechanisms may be involved in these organisms.
AB - Ultraviolet (UV) radiation has become an important stress factor in polar regions due to anthropogenically induced ozone depletion. Although extensive research has been conducted on adaptations of polar organisms to this stress factor, few studies have focused on semi-terrestrial algae so far, in spite of their apparent vulnerability. This study investigates the effect of UV on two semi-terrestrial arctic strains (B, G) and one Antarctic strain (E) of the green alga Zygnema, isolated from Arctic and Antarctic habitats. Isolates of Zygnema were exposed to experimentally enhanced UV A and B (predominant UV A) to photosynthetic active radiation (PAR) ratio. The pigment content, photosynthetic performance and ultrastructure were studied by means of high-performance liquid chromatography (HPLC), chlorophyll a fluorescence and transmission electron microscopy (TEM). In addition, phylogenetic relationships of the investigated strains were characterised using rbcL sequences, which determined that the Antarctic isolate (E) and one of the Arctic isolates (B) were closely related, while G is a distinct lineage. The production of protective phenolic compounds was confirmed in all of the tested strains by HPLC analysis for both controls and UV-exposed samples. Moreover, in strain E, the content of phenolics increased significantly (p = 0.001) after UV treatment. Simultaneously, the maximum quantum yield of photosystem II photochemistry significantly decreased in UV-exposed strains E and G (p < 0.001), showing a clear stress response. The phenolics were most probably stored at the cell periphery in vacuoles and cytoplasmic bodies that appear as electron-dense particles when observed by TEM after high-pressure freeze fixation. While two strains reacted moderately on UV exposure in their ultrastructure, in strain G, damage was found in chloroplasts and mitochondria. Plastidal pigments and xanthophyll cycle pigments were investigated by HPLC analysis; UV A- and UV B-exposed samples had a higher deepoxidation state as controls, particularly evident in strain B. The results indicate that phenolics are involved in UV protection of Zygnema and also revealed different responses to UV stress across the three strains, suggesting that other protection mechanisms may be involved in these organisms.
KW - Antarctic Regions
KW - Arctic Regions
KW - Chlorophyll/analysis
KW - Chlorophyll A
KW - Chromatography, High Pressure Liquid
KW - DNA, Plant/genetics
KW - Microscopy, Electron, Transmission
KW - Phenols/analysis
KW - Photosynthesis/radiation effects
KW - Photosystem II Protein Complex/radiation effects
KW - Phylogeny
KW - Streptophyta/chemistry
KW - Ultraviolet Rays
KW - Xanthophylls/analysis
UR - http://www.scopus.com/inward/record.url?scp=84872356068&partnerID=8YFLogxK
U2 - 10.1007/s00248-012-0096-9
DO - 10.1007/s00248-012-0096-9
M3 - Article
C2 - 22903087
AN - SCOPUS:84872356068
SN - 0095-3628
VL - 65
SP - 68
EP - 83
JO - Microbial Ecology
JF - Microbial Ecology
IS - 1
ER -
