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1 April 2003 Sensitivity of Cyanobacterial Antenna, Reaction Center and CO2 Assimilation Transcripts and Proteins to Moderate UVB: Light Acclimation Potentiates Resistance to UVB
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Abstract

We tested the hypothesis that cyanobacterial cells have sufficient acclimation potential to tolerate UVB when it is applied in a natural quantum ratio to growth photosynthetically active radiation (PAR). We grew Synechococcus under 50 (Low) or 300 (High) μmol PAR m−2·s−1 and then exposed the cells to 0.125 (Low) or 0.75 (High) μmol UVB m−2·s−1. The PAR:UVB quantum ratios were near natural for both the Low-PAR:Low-UVB and the High-PAR:High-UVB treatments, but UVB was in excess of typical aquatic PAR:UVB for Low-PAR:High-UVB treatments. The cellular light history determined the UVB responses of Synechococcus. High-PAR cells initially had fewer cpc transcripts encoding phycocyanin, lower phycocyanin content, and more psbAII/AIII transcripts encoding the D1:2 photosystem II (PSII) protein isoform. Higher PAR potentiated them to tolerate an appropriate UVB level without short-term inhibition of PSII or growth. Low-PAR cells rapidly altered psbAII/AIII and cpc gene expression and tolerated appropriate Low UVB. Low-PAR:High-UVB cells, in contrast, suffered short-term inhibition of PSII and growth. In all treatments UVB induced transient loss of cpc transcripts, possibly to free resources for psbAII/AIII expression, which is important for UVB resistance. The drop in cpc transcripts was not part of a general shock response because rbcL transcript pools were stable upon UVB exposure.

Tara M. MacDonald, Luc Dubois, Laura C. Smith, and Douglas A. Campbell "Sensitivity of Cyanobacterial Antenna, Reaction Center and CO2 Assimilation Transcripts and Proteins to Moderate UVB: Light Acclimation Potentiates Resistance to UVB," Photochemistry and Photobiology 77(4), 405-412, (1 April 2003). https://doi.org/10.1562/0031-8655(2003)077<0405:SOCARC>2.0.CO;2
Received: 30 August 2002; Accepted: 1 January 2003; Published: 1 April 2003
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