Complete Genome Structure of Gloeobacter violaceus PCC 7421, a Cyanobacterium that Lacks Thylakoids

Abstract

The nucleotide sequence of the entire genome of a cyanobacterium Gloeobacter violaceus PCC 7421 was determined. The genome of G. violaceus was a single circular chromosome 4,659,019 bp long with an average GC content of 62%. No plasmid was detected. The chromosome comprises 4430 potential protein-encoding genes, one set of rRNA genes, 45 tRNA genes representing 44 tRNA species and genes for tmRNA, B subunit of RNase P, SRP RNA and 6Sa RNA. Forty-one percent of the potential protein-encoding genes showed sequence similarity to genes of known function, 37% to hypothetical genes, and the remaining 22% had no apparent similarity to reported genes. Comparison of the assigned gene components with those of other cyanobacteria has unveiled distinctive features of the G. violaceus genome. Genes for PsaI, PsaJ, PsaK, and PsaX for Photosystem I and PsbY, PsbZ and Psb27 for Photosystem II were missing, and those for PsaF, PsbO, PsbU, and PsbV were poorly conserved. cpcG for a rod core linker peptide for phycobilisomes and nblA related to the degradation of phycobilisomes were also missing. Potential signal peptides of the presumptive products of petJ and petE for soluble electron transfer catalysts were less conserved than the remaining portions. These observations may be related to the fact that photosynthesis in G. violaceus takes place not in thylakoid membranes but in the cytoplasmic membrane. A large number of genes for sigma factors and transcription factors in the LuxR, LysR, PadR, TetR, and MarR families could be identified, while those for major elements for circadian clock, kaiABC were not found. These differences may reflect the phylogenetic distance between G. violaceus and other cyanobacteria.

slr1923 of Synechocystis sp. PCC6803 Is Essential for Conversion of 3,8-Divinyl(proto)chlorophyll(ide) to 3-Monovinyl(proto)chlorophyll(ide)

“…The results obtained in this study strongly suggest that the slr1923 gene product of Synechocystis 6803 is Nakamura et al, 2003). The sequence alignment among the homologues indicated that Gll0878 has higher sequence similarity with other cyanobacterial counterparts.…”

“…PCC6803 (Synechocystis 6803; Kaneko et al, 1996), Anabaena sp. PCC7120 (Kaneko et al, 2001), Thermosynechococcus elongatus BP-1 (Nakamura et al, 2002), and Gloeobacter violaceus PCC7421 (Nakamura et al, 2003), or the unicellular red alga Cyanidiochyzan merolae 10D (Matsuzaki et al, 2004). Based on the fact that these organisms synthesize MV-chl(ide), it is reasonable to assume that there exists an 8-vinyl reductase gene(s) whose amino acid sequence is rather different from those found in higher plants or C. tepidum.…”

The Histidine Kinase Hik34 Is Involved in Thermotolerance by Regulating the Expression of Heat Shock Genes in Synechocystis

“…WH8102 (Palenik et al, 2003), Prochlorococcus marinus MIT9313 (Rocap et al, 2003), P. marinus MED4 (Rocap et al, 2003), and P. marinus SS120 (Dufresne et al, 2003), as described by Mary and Vaulot (2003). Genes homologous to hik34 have also been found in the genomes of Gloeobacter violaceus PCC 7421 (Nakamura et al, 2003), Nostoc punctiforme (http://genome.jgi-psf. org/draft_microbes/nospu/nospu.home.html), and Trichodesmium erythraeum (http://genome.jgi-psf.org/ draft_ microbes/trier/trier.home.html).…”

PetC1 Is the Major Rieske Iron-Sulfur Protein in the Cytochrome b6f Complex of Synechocystis sp. PCC 6803

“…Although in many of the cyanobacterial genomes, such as in Synechococcus PCC 7002 and Anabaena PCC 7120, a petC gene family can be found, only the main petC gene, which is cotranscribed with petA, is present in the genomes of the thermophilic cyanobacterium Thermosynechococcus elongatus (39,40) and of the mesophilic cyanobacterium Gloeobacter violaceus PCC 7421 (41). Therefore, the occurrence of a petC gene family seems to be common but not obligatory in cyanobacteria.…”