CiteULike: llchristensens psba http://www.citeulike.org/user/llchristensen/tag/psba CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/llchristensen/article/2582808 <i>Plant Molecular Biology, Vol. 14, No. 1. (1 January 1990), pp. 81-92.</i><br /><br />The cyanobacterium Anabaena PCC 7120 contains a multigene family that encodes the D1 polypeptide of Photosystem II. This family consists of four members denoted psbAI-IV that are each unique but highly homologous. psbAII, III and IV are more closely related to each other than to psbAI. These three copies encode identical polypeptides that differ from the psbAI product by 21 amino acids. The transcription initiation site for psbAI has been mapped to 64–65 nucleotides upstream from the coding region. Primer extension assays performed with an oligonucleotide specific for psbAII, III and IV transcripts suggest that one or more of these genes is also expressed. Genomic mapping and chromosome walking experiments demonstrate that none of the four psbA copies is within 20 kbp of another member of the gene family. Characterization of a four-member psbA gene family from the cyanobacterium Anabaena PCC 7120 Jacqueline Vrba Stephanie Curtis doi:10.1007/BF00015657 Plant Molecular Biology, Vol. 14, No. 1. (1 January 1990), pp. 81-92. 2008-03-24T21:16:38-00:00 Plant Molecular Biology 14 1 81 92 anabaena fam psba http://www.citeulike.org/user/llchristensen/article/2582804 <i>Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol. 1757, No. 1. (January 2006), pp. 47-56.</i><br /><br />Cyanobacteria cope with UVB induced photoinhibition of Photosystem II by regulating multiple psbA genes to boost the expression of D1 protein (in Synechocystis sp. PCC6803), or to exchange the constitutive D1:1 protein to an alternate D1:2 isoform (in Synechococcus sp. PCC7942). To define more general patterns of cyanobacterial psbA expression, we applied moderately photoinhibitory UVB to Anabaena sp. PCC7120 and tracked the expression of its five psbA genes. psbAI, encoding a D1:1 protein isoform characterized by a Gln130, represented the majority of the psbA transcript pool under control conditions. psbAI transcripts decreased upon UVB treatment but the total psbA transcript pool increased 3.5 fold within 90 min as a result of sharply increased psbAII, psbAIV and psbAIII transcripts encoding an alternate D1:2 protein isoform characterized by Glu130, similar to that of Synechococcus. Upon UVB treatment the relaxation of flash induced chlorophyll fluorescence showed a characteristic acceleration of a decay phase likely associated with the exchange from the D1:1 protein isoform encoded by psbAI to the alternate D1:2 isoform encoded by psbAIV, psbAII and psbAIII. Throughout the UVB treatment the divergent psbA0 made only a trace contribution to the total psbA transcript pool. This suggests a similarity to the divergent psbAI gene from Synechocystis, whose natural expression we demonstrate for the first time at a trace level similar to psbA0 in Anabaena. These trace-expressed psbA genes in two different cyanobacteria raise questions concerning the functions of these divergent genes. Cyanobacterial psbA families in Anabaena and Synechocystis encode trace, constitutive and UVB-induced D1 isoforms Cosmin Sicora Sarah Appleton Christopher Brown Jonathon Chung Jillian Chandler Amanda Cockshutt Imre Vass Douglas Campbell doi:10.1016/j.bbabio.2005.11.002 Biochimica et Biophysica Acta (BBA) - Bioenergetics, Vol. 1757, No. 1. (January 2006), pp. 47-56. 2008-03-24T21:13:44-00:00 Biochimica et Biophysica Acta (BBA) - Bioenergetics 1757 1 47 56 fam psba uvb