Inverted repeat of Olisthodiscus luteus chloroplast DNA contains genes for both subunits of ribulose-1,5-bisphosphate carboxylase and the 32,000-dalton Q _B protein: Phylogenetic implications

Abstract

The chloroplast DNA of the chromophytic alga Olisthodiscus luteus has been physically mapped with four restriction enzymes. An inverted repeat of 22 kilobase pairs is present in this 150-kilobase-pair plastid genome. The inverted repeat contains the genes for the large and small subunit polypeptides of ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) and also codes for the 32,000-dalton QB protein.These observations demonstrate that significant differences exist in chloroplast genome structure and organization among major plant taxa.In recent years, the concept of an endosymbiotic origin for chloroplasts has been generally accepted. Data

Analysis of Chromophytic and Rhodophytic Ribulose-1,5-Bisphosphate Carboxylase Indicates Extensive Structural and Functional Similarities among Evolutionarily Diverse Algae

“…The rbcS gene is encoded in the nuclear genome of land plants (3) and in the alga Chlamydomonas reinhardtii (14). In contrast, data obtained from Olisthodiscus luteus demonstrates that the rbcS gene is located 3' to rbcL in the chloroplast of this goldenbrown eukaryotic alga (36). Unexpectedly, the rbcS gene encodes a polypeptide with a predicted amino acid sequence that is most similar to the Rubisco SS of the chemolithotrophic bacterium, Alcaligenes eutrophus (5).…”

Structural, Functional, and Evolutionary Analysis of Ribulose-1,5-Bisphosphate Carboxylase from the Chromophytic Alga Olisthodiscus luteus

“…These data demonstrate that a high degree of RuBPCase conservation occurs among widely divergent photoautotrophs regardless of small subunit coding site. Photoautotrophy in eukaryotic cells is hypothesized to have occurred approximately 1.5 billion years ago when a colorless host cell phagocytosed and maintained a photosynthetic prokaryote as a symbiont. Controversy exists on whether this early host/prokaryotic relationship occurred in a monophyletic or polyphyletic manner (4,20). A monophyletic scheme suggests that the symbiotic event which took place in early evolutionary time involved a single ancestor-host interaction whereas a polyphyletic origin implies that more than one type of ancestral symbiont existed and thus many different host-symbiont associations could have occurred.…”

“…Speculation on whether chloroplast DNA (ctDNA) coding profile and gene arrangement are similar or vastly different among these phylogenetic groups has been hampered by a paucity of information on ctDNA in nonchlorophytic plants. Recent studies in our laboratory have focused on an analysis of the coding site of the important photosynthetic enzyme RuBPCase.2 Although all chlorophytes code for the LS and SS of this enzyme in the nucleus and chloroplast, respectively (11,30), in the chromophytic alga Olisthodiscus luteus, immunoprecipitation of protein products synthesized in the presence of the cytoplasmic ribosome inhibitor cycloheximide gives evidence that both subunits of RuBPCase are synthesized in the chloroplast (20). Expression of the LS and SS polypeptides in a linked transcription-translation system using a cloned 0. luteus ctDNA fragment demonstrates (20) definitively that both genes are encoded on the plastid genome.…”

“…Recent studies in our laboratory have focused on an analysis of the coding site of the important photosynthetic enzyme RuBPCase.2 Although all chlorophytes code for the LS and SS of this enzyme in the nucleus and chloroplast, respectively (11,30), in the chromophytic alga Olisthodiscus luteus, immunoprecipitation of protein products synthesized in the presence of the cytoplasmic ribosome inhibitor cycloheximide gives evidence that both subunits of RuBPCase are synthesized in the chloroplast (20). Expression of the LS and SS polypeptides in a linked transcription-translation system using a cloned 0. luteus ctDNA fragment demonstrates (20) definitively that both genes are encoded on the plastid genome. The rbcL and rbcS genes are present on a large 20 kb inverted repeat which also contains psbA and ribosomal RNA cistrons (20) (TP Delaney, RA Cattolico, unpublished data).…”

Characterisation of a chloroplast‐encoded sec Y homologue and atpH from a chromophytic alga Evidence for a novel chloroplast genome organisation

“…The chloroplasl genomes of algae show a greater diversity of size, ranging from 84 kb to 600 kb [2] whereas those of the chromophytic algae for which there is much less information available, fall within the range of t00 to 160 kb [2]. There are indications, based on nucleotide sequence data for the Rubisco genes, rbcL and rbcS, that the chromophytic alga contain several genes that are similar to prokaryotic genes but which are not present in higher plant and green algal chloroplast DNA [3]. Some genes involved in protein translocation have also been retained on the chloroplast genome of eukaryotic algae outside of the chlorophyta [4][5][6].…”