Disease relevance of psbA1

• Nucleotide sequence of a member of the psbA multigene family from the unicellular cyanobacterium Synechocystis 6803 [1].
• However, the psbA1 gene product contained five extra amino acids, which were not found in PsbA proteins from five other cyanobacteria [2].
• Results indicated that SigE also contributes to light-induced transcription on the cpcBACD, psbA, petBD and psaAB promoters whose potential sequences are of the Escherichia coli sigma(70)-type [3].
• Cyanobacterial psbA families in Anabaena and Synechocystis encode trace, constitutive and UVB-induced D1 isoforms [4].

High impact information on psbA1

• The silent and divergent psbA1 copy of the psbA gene family was activated by exchanging part of its upstream region with a corresponding fragment of the psbA2 copy [5].
• Another mutant containing the activated psbA1 gene together with the psbA2 and psbA3 genes produced both the D1 and D1' proteins [5].
• Eight novel point mutations in the gene psbA, which encodes D1, were generated in the cyanobacterium Synechocystis PCC6803 by site-specific mutagenesis in vitro [6].
• The psbA gene codes for the D1 polypeptide of the photosystem II reaction center complex and is found in all photosynthetic organisms that carry out oxygenic photosynthesis [7].
• Here we describe the construction and characterization of a strain of the cyanobacterium Synechocystis sp PCC 6803 in which the three endogenous psbA genes are replaced by a single psbA gene from the chloroplast genome of the higher plant Poa annua [7].

Chemical compound and disease context of psbA1

• By activation of the silent and divergent psbA1 gene in the cyanobacterium Synechocystis 6803, a novel D1 protein, D1', was produced [Salih, G. & Jansson, C. (1997) Plant Cell 9, 869-878] [8].
• To test this hypothesis, we have changed Tyr-161 to phenylalanine by site-directed mutagenesis of a psbA gene in Synechocystis [9].
• Accumulation and stability of psbA and rbcL-S transcripts in Synechocystis 6803 was followed in the presence and absence of the photosynthesis inhibitors DCMU and methylviologen [10].
• Mutation in phenol-type herbicide resistance maps within the psbA gene in Synechocystis 6714 [11].
• A Synechocystis strain 6803 psbA mutant strain grows under light-pulsed conditions at rates similar to those for the glucose-tolerant strain, indicating that photosystem II is not required for growth [12].

Biological context of psbA1

• To understand the mechanisms underlying the light sensitivity of D1, we performed in vitro random mutagenesis of the psbA gene that codes for D1, transformed the unicellular cyanobacterium Synechocystis sp. PCC 6803 with mutated psbA, and selected phototolerant transformants that did not bleach in high intensity light [13].
• Accumulation of monomer and dimer photosystem (PS) II reaction center core complexes has been analyzed by two-dimensional Blue-native/SDS-PAGE in Synechocystis PCC 6803 wild type and in mutant strains lacking genes psbA, psbB, psbC, psbDIC/DII, or the psbEFLJ operon [14].
• We investigated the role of the redox state of the photosynthetic and respiratory electron transport chains on the regulation of psbA expression in Synechocystis PCC 6803 [15].
• Redox control of psbA gene expression in the cyanobacterium Synechocystis PCC 6803. Involvement of the cytochrome b(6)/f complex [15].
• We show that changes in the redox state of the intersystem electron transport chain induce modifications of psbA transcript production and psbA mRNA stability [15].

Anatomical context of psbA1

• Cytosolic ribosomes were attached to psbA transcripts in the dark, and translation continued up to a distinct pausing site [16].
• Subcellular localization of polysomes with bound psbA mRNAs suggested that the primary target of singlet oxygen might be the elongation step of translation [17].
• However, the degradation rate of psbA transcript, as well as of other transcripts encoding proteins of thylakoid complexes, is down-regulated in all conditions leading to the oxidation of the plastoquinone pool [18].
• Experiments to measure newly synthesized D1 incorporation into the thylakoid membranes during recovery in the presence of rifampicin showed that the initiation of transcription was not required for translation of psbA mRNA when photoinhibition was still reversible [19].

Associations of psbA1 with chemical compounds

• Novel psbA1 gene from a naturally occurring atrazine-resistant cyanobacterial isolate [2].
• Our data suggest that the redox state of one of the electron carriers between the plastoquinone pool and the photosystem I has opposite influences on psbA and psaE expression [20].
• Inhibition of the plastoquinone pool reduction by DCMU or its oxidation by DBMIB does not diminish the transcription of the psbA gene under growth conditions [18].
• The mutation found in the psbA gene (encoding the D 1 photosystem II protein) is at the same codon 266 as for the first ioxynil-resistant mutant IoxIA previously selected [G. Ajlani, I. Meyer, C. Vernotte, and C. Astier, FEBS Lett. 246, 207-210 (1989)] [21].

Other interactions of psbA1

• The light-regulated expression of the activated psbA1 gene showed that the inserted psbA2 segment contains the information necessary for light-dependent as well as high-light-stimulated transcription [5].

Analytical, diagnostic and therapeutic context of psbA1

• Northern- and western-blotting analyses demonstrated that salt stress inhibited the transcription and the translation of psbA genes, which encode D1 protein [22].
• Northern blotting analysis indicated that the accumulation of psbA mRNAs, which encode the D1 protein, was unaffected by the production of singlet oxygen [17].

References