Arctic, antarctic, and temperate green algae Zygnema spp. under UV-B stress: Vegetative cells perform better than pre-akinetes.
    
    
        
    
    
        
        Protoplasma 255, 1239-1252 (2018)
    
    
    
      
      
	
	    Species of Zygnema form macroscopically visible mats in polar and temperate terrestrial habitats, where they are exposed to environmental stresses. Three previously characterized isolates (Arctic Zygnema sp. B, Antarctic Zygnema sp. C, and temperate Zygnema sp. S) were tested for their tolerance to experimental UV radiation. Samples of young vegetative cells (1 month old) and pre-akinetes (6 months old) were exposed to photosynthetically active radiation (PAR, 400–700 nm, 400 μmol photons m −2 s −1 ) in combination with experimental UV-A (315–400 nm, 5.7 W m −2 , no UV-B), designated as PA, or UV-A (10.1 W m −2 ) + UV-B (280–315 nm, 1.0 W m −2 ), designated as PAB. The experimental period lasted for 74 h; the radiation period was 16 h PAR/UV-A per day, or with additional UV-B for 14 h per day. The effective quantum yield, generally lower in pre-akinetes, was mostly reduced during the UV treatment, and recovery was significantly higher in young vegetative cells vs. pre-akinetes during the experiment. Analysis of the deepoxidation state of the xanthophyll-cycle pigments revealed a statistically significant (p < 0.05) increase in Zygnema spp. C and S. The content of UV-absorbing phenolic compounds was significantly higher (p < 0.05) in young vegetative cells compared to pre-akinetes. In young vegetative Zygnema sp. S, these phenolic compounds significantly increased (p < 0.05) upon PA and PAB. Transmission electron microscopy showed an intact ultrastructure with massive starch accumulations at the pyrenoids under PA and PAB. A possible increase in electron-dense bodies in PAB-treated cells and the occurrence of cubic membranes in the chloroplasts are likely protection strategies. Metabolite profiling by non-targeted RP-UHPLC-qToF-MS allowed a clear separation of the strains, but could not detect changes due to the PA and PAB treatments. Six hundred seventeen distinct molecular masses were detected, of which around 200 could be annotated from databases. These results indicate that young vegetative cells can adapt better to the experimental UV-B stress than pre-akinetes.
	
	
	    
	
       
      
	
	    
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        Publication type
        Article: Journal article
    
 
    
        Document type
        Scientific Article
    
 
    
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        Keywords
        Uv-a ; Uv-b ; Uv Simulation ; Green Algae ; Ultrastructure ; Metabolomics
    
 
    
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        Publication Year
        2018
    
 
    
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        HGF-reported in Year
        2018
    
 
    
    
        ISSN (print) / ISBN
        0033-183X
    
 
    
        e-ISSN
        1615-6102
    
 
    
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	    Volume: 255,  
	    Issue: 4,  
	    Pages: 1239-1252 
	    Article Number: ,  
	    Supplement: ,  
	
    
 
    
        
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            Springer
        
 
        
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        Reviewing status
        Peer reviewed
    
 
     
    
        POF-Topic(s)
        30202 - Environmental Health
    
 
    
        Research field(s)
        Environmental Sciences
    
 
    
        PSP Element(s)
        G-504991-001
G-504800-001
    
 
    
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        Erfassungsdatum
        2018-06-14