A study of chlorophyll-like and phycobilin pigments in the C endosymbiont of the apple- snail Pomacea canaliculata

Pigments present in the brown-greenish C morph of an intracellular endosymbiont of Pomacea canaliculata were investigated. Acetone extracts of the endosymbiotic corpuscles showed an absorption spectrum similar to that of chlorophylls. Three fractions obtained from silica gel column chromatography of the acetone extracts (C I, C II and C III), were studied by positive ion fast atom bombardment-mass spectrometry (FAB-MS) and hydrogen-nuclear magnetic resonance (H-NMR). Results indicated the presence of (1) a sterol in the yellow colored C I fraction; (2) a mixture of pheophorbides a and b in the major green fraction, C II; and (3) a modified pheophorbide a in the smaller green fraction, C III. Aqueous extracts of the C endosymbiont did not show evidence of the occurrence of C-phycocyanin, allophycocyanin or phycoerithrin (light absorption, fluorescence emission, and electrophoresis of the protein moieties) while cyanobacterial cells (Nostoc sp.) showed evidence of C-phycocyanin and allophycocyanin. The possible phylogenetic and functional significance of the pigments present in the C endosymbiont is discussed.

The upstream sequence of the phycocyanin b subunit gene from Arthrospira platensis regulates expression of gfp gene in response to light intensity

In cyanobacteria, few details are known of the mechanisms through which the expression of the light-harvesting pigment c-phycocyanin is regulated. In the present study, a 419 bp upstream sequence of the phycocyanin b subunit (cpcB) gene from Arthrospira platensis FACHB341 was fused with green fluorescent protein (gfp) gene, and a heterologous reporting system was built up to investigate the influence of light intensity on the expression of gfp gene, and the regulation function of different region of the upstream sequence of cpcB gene. Results showed that the upstream sequence of cpcB gene could drive the expression of gfp gene in Synechococcus sp. strain PCC7942, and the expression was influenced by light intensity, the lower the light intensity, the higher the GFP level. Deletion analysis revealed that a light-responsive element was located in the region -276 to-218, a promoter sequence was in the region -85 to -1, and two positive cis elements were in the -419 to -276 and the -218 to -130 regions, respectively.