Studies On C-phycocyanin Operon And Rubisco Gene Of Arthrospira Platensis FACHB341 And Molecular Phylogenetics In Arthrospira And Spirulina

The C-phycocyanin (cpc) operon of blue-green alga (or cyanobacteria) Arthrospira platensis FACHB341 was cloned, sequenced and characterized by using chromoseme walking method. The sequence includes cpcB gene (519 bp), cpcA gene (489 bp), cpcH gene (357 bp), and upstream sequence of cpcB (427 bp) and upstream sequence of cpcH genes (184 bp), 111 bp of phycocyanin intergenetic spacer (PC- IGS). Upstream sequence of cpcB gene was ligated into promoter-probe vector pEGFP-1 and transformed into three systems: E. coli, Synechocystis PCC 6803 and A. platensis FACHB341 by supersonic and electrophoresis methods. Green fluorescence of GFP was detected in Synechocysistis PCC 6803, which displays that this fragment has promoter activity. Five putative promoter sequences was predicted, four lie in the upstream sequence of cpcB gene and one in the upstream sequence of cpcH gene. Further analysis showed that there are regulatory elements, including TATA box and CAAT box, etc.PC-IGS fragments were cloned and sequenced from five strains of Arthrospira (A. platensis FACHB341, A. platensis FACHB439, A. platensis OUQDS6, A. maxima OUQDSM and A. platensis FACHB791) and two strains of Spirulina (S. subsalsa FACHB351 and Spirulina FACHB440). The cloned fragment includes 494 bp of cpcB, 252 bp of cpcAand 111 bp of PC-IGS sequence. Similarity analysis shows that some results were incongruent with the traditional taxonomy, e.g. S. subsalsa FACHB351 is more similar with Arthrospira than that with Spirulina, and A. platensis FACHB439 has a higher similarity with Spirulina FACHB440 than with the other strains.rbcL gene was cloned, sequenced and characterized in A. platensis FACHB341, A. platensis FACHB439, A. maxima OUQDSM and Spirulina sp. FACHB440. Resultsshowed that GC content of the gene in strain Spirulina sp. FACHB440 was higher than that in the others. Alignment based on deduced amino acid sequences indicated that Spirulina FACHB440 was different from that in other three samples of Arthrospira. Nucleotide sequence similarity among the three strains of the genus of Arthrospira (96.5-99.6%) was higher than that between Arthrospira and Spirulina (78.1-78.5%). Phylogenetic tree was constructed and displayed that A. platensis FACHB341, A. maxima OUQDSM and A. platensis FACHB439 formed the monophyletic linage, which was fully supported by bootstrap values (1000), while Spirulina FACHB440 and Anabaena PCC7120 clustered in another linage with the bootstrap value of 909.2073 bp fragment of rubisco was cloned, sequenced and analyzed from A. platensis FACHB341, including partial sequence of rbcL gene, rbcX gene and rbcS gene. There are two transcription stem-loop termination structures downstream of the 3' sequence of rbcL gene. The deduced amino acid sequence of rbcL and rbcS includes 13.14% acidic amino acid and 14.51% aliphatic amino acid, the hydrophobic amino acid is 42.16%. The similarity of rbcL gene with homologous gene sequences in Agmenellum quadruplicatum, Synechocystis PCC6803, Synechococcus PCC6301, Prochlorothrix hollandica and Anabaena PCC7120 is 77.2%, 81.7%, 74.8%, 79.9% and 76.1%, respectively. Similarities of rbcS gene with homologous gene in four Anabaena sp. sequences are all 67.6%, but it is 30.1% with one Synechococcus sp. and 63.8% with the other one.