NUCLEOTIDE-SEQUENCE OF THE GENE FOR THE LARGE SUBUNIT OF RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE OXYGENASE FROM CRYPTOMONAS-PHI - EVIDENCE SUPPORTING THE POLYPHYLETIC ORIGIN OF PLASTIDS

The chloroplast-encoded gene for the large subunit of ribulose-1,5-bisphosphate carboxylase / oxygenase (Rubisco) from the marine chlorophyll c2-, phycobiliprotein-containing alga, Cryptomonas phi was cloned, sequenced and compared to representatives from other groups of photo-synthetic organisms. The coding sequence was 1464 base pairs (bp) and encoded a polypeptide of 488 amino acids. The small subunit of Rubisco was located 83 bp 3' to the large subunit and was co-transcribed. A 5 bp sequence, 5' of the initiator methionine codons of both the large and small subunits, may represent ribosomal binding sites. The start of transcription was identified by primer extension studies and putative promoter sequences were found. This study is the first report of the sequence for the large subunit of Rubisco from a chromophyte alga, and its potential as a phylogenetic indicator for algal plastids is discussed.