The small subunit of ribulose-1,5-bisphosphate carboxylase is plastid-encoded in the chlorophyll c-containing alga Cryptomonas ?

Abstract

The gene for the small subunit of ribulose-1,5-bisphosphate carboxylase (Rubisco) is located in the large single-copy region of the plastid genome of the chlorophyll c-containing alga Cryptomonas phi. The coding sequence is 417 base pairs long, encoding a protein of 139 amino acids, considerably longer than most other small subunit proteins. It is found 83 base pairs downstream from the gene for the large subunit and is cotranscribed with it. An 18 base pair perfect inverted repeat is located 8 base pairs beyond the termination codon. Sequence analysis shows the gene to be more closely related to cyanobacterial and cyanelle small-subunit genes than to those of green algae or land plants. This is the first reported sequence of a Rubisco small-subunit gene which is plastid-encoded and it exhibits a number of unique features. The derived amino acid sequence shows extensive similarity to a partial amino acid sequence from a brown alga, indicating that this gene will be of major interest as a probe for the small subunit genes in other algae and for determining possible evolutionary ancestors of algal plastids.

Rubisco genes indicate a close phylogenetic relation between the plastids of Chromophyta and Rhodophyta

“…The rbcS gene was detected downstream of the rbcL gene by sequence analysis. Both Rubisco genes were separated by an A/T-rich spacer of 178 bp which is comparable to the situation found in red algae [41,42], Cryptomonas ~P [7], Olisthodiscus luteus [ 2 ], Cyanophora paradoxa [ 36 ] and cyanobacteria [31,35]. Spacer lengths in these organisms vary between 48 bp (Cyanidium caldarium) and 545 bp (Anabaena 7120, Fig.…”

“…RbcS genes from chlorophyll a/b plants are clearly distinct from those of the aforesaid algae. The rbcS gene is nuclear-encoded in chlorophyll a/b plants [32] and resides on the plastid DNA (ptDNA) in all other plants analyzed so far [7,17,33,36,41,42]. As different mutation rates must be assumed in different genetic compartments analysis of a gene which is always ptDNAencoded is a prerequisite to further clarify the phylogenetic relationship between rhodoplasts and chloroplasts.…”

“…= Porphyridum aerugineum (Rhodophyta,[41]); Cryp. = Cryptomonas ~ (Cryptophyta,[7]); O.lut. = Olisthodiscus luteus (Chromophyta, Chrysophyceae,[2]); E. sil.…”

The plastid genome of Cryptomonas phi encodes an hsp70-like protein, a histone-like protein, and an acyl carrier protein.

“…The plastid genome of Cryptomonas 4) has been shown to be a circular DNA of 118 kilobase pairs (kbp), containing an inverted repeat of less than 6 kbp within which the plastid rRNA genes are located (14). Several genes of this genome have been described previously, including the rbcS gene, whose counterpart in plants is encoded in the nuclear genome (7). In this paper, we present the structures of three genes found in the plastid genome of Cryptomonas 4) that encode an hsp70-like heat shock protein, a histone-like protein, and an acyl carrier protein.t To date, so far as we know, these genes have not been reported for any other organellar genome, and each of them represents a functional class of organellar gene product not described previously.…”

Molecular systematics of the genera <i>Laurencia, Osmundea</i> and <i>Palisada</i> (Rhodophyta) from the Canary Islands - Analysis of rDNA and RUBISCO spacer sequences

“…for the spacer in the Laurencia, Osmundea and Palisada species ranges between 76-80%, which is similar to other algal species as Cryptomonas sp., Olisthodiscus luteus and Pylaeilla littoralis Douglas & Durnford, 1989;Delaney & Cattolico, 1989;Assali & al., 1991). Towards the 3' end of the spacer in all the Laurencia, Osmundea and Palisada species examined, there is a purine rich sequence ( 5' AAGGAG 3'…”