Structure and light regulation of genes encoding phycocyanin and allophycocyanin from Spirulina platensis C1
1997
Morakot Tanticharoen | Suchada Chaisawadi | Marsac, Nicole Tandeau De | Pinthipya Nomsawai | Wattana Jeamton | Dauenpen Meesupyodsuk | Supapon Cheevadhanarak(King Mongkut's Institute of Technology Thonburi, Bangkok (Thailand). School of Bioresources and Technology)
Gene clones encoding phycocyanin and allophycocyanin, phycobiliproteins comprising phycobilisomes of Spirulina platensis C1, were isolated from lambdaDASHII library using PCR fragments of phycocyanin (cpc) gene and allophycocyanin (apc) of S. platensis C1 as homologous probes. Both cpc and apc genes appeared to be present in only one copy per genome and were organized in the form of operons in order as cpcB-cpcA and apcA-apcB, respectively. Using specific probes, Northern analysis revealed that the transcripts of these two genes accumulated to high levels in low light grown cells and low levels in high light grown cells. It was found that in low light irridiance cpc genes were transcribed to give 3 types of transcripts with the abundance of 1.4, 1.5 kilobase (kb) RNAs and a less prominent 3.5 kb, while in high light, the 3.5 kb disappeared completely. In high light irridiance, the decrease in size of phycobilisomes could be observed of which the result was in accordance with the disappearance of the 3.5 kb transcript of cpc genes. In contrast to cpc genes, the 2 types of transcripts of apc genes, a 1.4 kb predominant RNA and a minor 1.7 kb, were observed in both low light and high light grown cells. These findings established the occurrence of transcription regulation for the expression of both cpc and apc operons as well as modulation of the size of phycobilisomes in response to light intensity changes.
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