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Robert K. Jansen - One of the best experts on this subject based on the ideXlab platform.
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coevolution between nuclear encoded dna replication recombination and repair genes and Plastid Genome complexity
Genome Biology and Evolution, 2016Co-Authors: Jin Zhang, John C Blazier, Maolun Weng, Robert K. Jansen, Jamal S. M. Sabir, Tracey A Ruhlman, Seongjun ParkAbstract:Disruption of DNA replication, recombination, and repair (DNA-RRR) systems has been hypothesized to cause highly elevated nucleotide substitution rates and Genome rearrangements in the Plastids of angiosperms, but this theory remains untested. To investigate nuclear-Plastid Genome (plastome) coevolution in Geraniaceae, four different measures of plastome complexity (rearrangements, repeats, nucleotide insertions/deletions, and substitution rates) were evaluated along with substitution rates of 12 nuclear-encoded, Plastid-targeted DNA-RRR genes from 27 Geraniales species. Significant correlations were detected for nonsynonymous (dN) but not synonymous (dS) substitution rates for three DNA-RRR genes (uvrB/C, why1, and gyrA) supporting a role for these genes in accelerated Plastid Genome evolution in Geraniaceae. Furthermore, correlation between dN of uvrB/C and plastome complexity suggests the presence of nucleotide excision repair system in Plastids. Significant correlations were also detected between plastome complexity and 13 of the 90 nuclear-encoded organelle-targeted genes investigated. Comparisons revealed significant acceleration of dN in Plastid-targeted genes of Geraniales relative to Brassicales suggesting this correlation may be an artifact of elevated rates in this gene set in Geraniaceae. Correlation between dN of Plastid-targeted DNA-RRR genes and plastome complexity supports the hypothesis that the aberrant patterns in angiosperm plastome evolution could be caused by dysfunction in DNA-RRR systems.
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reconstruction of the ancestral Plastid Genome in geraniaceae reveals a correlation between Genome rearrangements repeats and nucleotide substitution rates
Molecular Biology and Evolution, 2014Co-Authors: Maolun Weng, John C Blazier, Madhumita Govindu, Robert K. JansenAbstract:Geraniaceae Plastid Genomes are highly rearranged, and each of the four genera already sequenced in the family has a distinct Genome organization. This study reports Plastid Genome sequences of six additional species, Francoa sonchifolia, Melianthus villosus, and Viviania marifolia from Geraniales, and Pelargonium alternans, California macrophylla, and Hypseocharis bilobata from Geraniaceae. These Genome sequences, combined with previously published species, provide sufficient taxon sampling to reconstruct the ancestral Plastid Genome organization of Geraniaceae and the rearrangements unique to each genus. The ancestral Plastid Genome of Geraniaceae has a 4 kb inversion and a reduced, Pelargonium-like small single copy region. Our ancestral Genome reconstruction suggests that a few minor rearrangements occurred in the stem branch of Geraniaceae followed by independent rearrangements in each genus. The genomic comparison demonstrates that a series of inverted repeat boundary shifts and inversions played a major role in shaping Genome organization in the family. The distribution of repeats is strongly associated with breakpoints in the rearranged Genomes, and the proportion and the number of large repeats (>20 bp and >60 bp) are significantly correlated with the degree of Genome rearrangements. Increases in the degree of Plastid Genome rearrangements are correlated with the acceleration in nonsynonymous substitution rates (dN) but not with synonymous substitution rates (dS). Possible mechanisms that might contribute to this correlation, including DNA repair system and selection, are discussed.
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Implications of the Plastid Genome Sequence of Typha (Typhaceae, Poales) for Understanding Genome Evolution in Poaceae
Journal of Molecular Evolution, 2010Co-Authors: Mary M. Guisinger, Jeffrey L. Boore, Jennifer V. Kuehl, Timothy W. Chumley, Robert K. JansenAbstract:Plastid Genomes of the grasses (Poaceae) are unusual in their organization and rates of sequence evolution. There has been a recent surge in the availability of grass Plastid Genome sequences, but a comprehensive comparative analysis of Genome evolution has not been performed that includes any related families in the Poales. We report on the Plastid Genome of Typha latifolia , the first non-grass Poales sequenced to date, and we present comparisons of Genome organization and sequence evolution within Poales. Our results confirm that grass Plastid Genomes exhibit acceleration in both genomic rearrangements and nucleotide substitutions. Poaceae have multiple structural rearrangements, including three inversions, three genes losses ( accD , ycf1 , ycf2 ), intron losses in two genes ( clpP , rpoC 1), and expansion of the inverted repeat (IR) into both large and small single-copy regions. These rearrangements are restricted to the Poaceae, and IR expansion into the small single-copy region correlates with the phylogeny of the family. Comparisons of 73 protein-coding genes for 47 angiosperms including nine Poaceae genera confirm that the branch leading to Poaceae has significantly accelerated rates of change relative to other monocots and angiosperms. Furthermore, rates of sequence evolution within grasses are lower, indicating a deceleration during diversification of the family. Overall there is a strong correlation between accelerated rates of genomic rearrangements and nucleotide substitutions in Poaceae, a phenomenon that has been noted recently throughout angiosperms. The cause of the correlation is unknown, but faulty DNA repair has been suggested in other systems including bacterial and animal mitochondrial Genomes.
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Extensive Reorganization of the Plastid Genome of Trifolium subterraneum (Fabaceae) Is Associated with Numerous Repeated Sequences and Novel DNA Insertions
Journal of Molecular Evolution, 2008Co-Authors: Mary Guisinger, John C Blazier, Jennifer V. Kuehl, Elizabeth Ruck, Vanity Mcmurtry, Jeffrey Boore, Robert K. JansenAbstract:The Plastid Genome of Trifolium subterraneum is 144,763 bp, about 20 kb longer than those of closely related legumes, which also lost one copy of the large inverted repeat (IR). The Genome has undergone extensive genomic reconfiguration, including the loss of six genes ( accD, infA, rpl22, rps16, rps18 , and ycf1 ) and two introns ( clpP and rps12 ) and numerous gene order changes, attributable to 14–18 inversions. All endpoints of rearranged gene clusters are flanked by repeated sequences, tRNAs, or pseudogenes. One unusual feature of the Trifolium subterraneum Genome is the large number of dispersed repeats, which comprise 19.5% (ca. 28 kb) of the Genome (versus about 4% for other angiosperms) and account for part of the increase in Genome size. Nine genes ( psbT , rbcL , clpP , rps3 , rpl23 , atpB , psbN , trnI -cau, and ycf3 ) have also been duplicated either partially or completely . rpl23 is the most highly duplicated gene, with portions of this gene duplicated six times. Comparisons of the Trifolium Plastid Genome with the Plant Repeat Database and searches for flanking inverted repeats suggest that the high incidence of dispersed repeats and rearrangements is not likely the result of transposition. Trifolium has 19.5 kb of unique DNA distributed among 160 fragments ranging in size from 30 to 494 bp, greatly surpassing the other five sequenced legume Plastid Genomes in novel DNA content. At least some of this unique DNA may represent horizontal transfer from bacterial Genomes. These unusual features provide direction for the development of more complex models of Plastid Genome evolution.
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complete Plastid Genome sequence of the chickpea cicer arietinum and the phylogenetic distribution of rps12 and clpp intron losses among legumes leguminosae
Molecular Phylogenetics and Evolution, 2008Co-Authors: Robert K. Jansen, Martin F Wojciechowski, Elumalai Sanniyasi, Henry DaniellAbstract:Chickpea (Cicer arietinum, Leguminosae), an important grain legume, is widely used for food and fodder throughout the world. We sequenced the complete Plastid Genome of chickpea, which is 125,319 bp in size, and contains only one copy of the inverted repeat (IR). The Genome encodes 108 genes, including 4 rRNAs, 29 tRNAs, and 75 proteins. The genes rps16, infA, and ycf4 are absent in the chickpea Plastid Genome, and ndhB has an internal stop codon in the 5′exon, similar to other legumes. Two genes have lost their introns, one in the 3′exon of the transpliced gene rps12, and the one between exons 1 and 2 of clpP; this represents the first documented case of the loss of introns from both of these genes in the same Plastid Genome. An extensive phylogenetic survey of these intron losses was performed on 302 taxa across legumes and the related family Polygalaceae. The clpP intron has been lost exclusively in taxa from the temperate “IR-lacking clade” (IRLC), whereas the rps12 intron has been lost in most members of the IRLC (with the exception of Wisteria, Callerya, Afgekia, and certain species of Millettia, which represent the earliest diverging lineages of this clade), and in the tribe Desmodieae, which is closely related to the tribes Phaseoleae and Psoraleeae. Data provided here suggest that the loss of the rps12 intron occurred after the loss of the IR. The two new genomic changes identified in the present study provide additional support of the monophyly of the IR-loss clade, and resolution of the pattern of the earliest-branching lineages in this clade. The availability of the complete chickpea Plastid Genome sequence also provides valuable information on intergenic spacer regions among legumes and endogenous regulatory sequences for Plastid genetic engineering.
Pál Maliga - One of the best experts on this subject based on the ideXlab platform.
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New Tools for Engineering the Arabidopsis Plastid Genome.
Plant Physiology, 2019Co-Authors: Lisa M. Lamanna, Megan E. Kelly, Kerry Lutz, Pál MaligaAbstract:New transformation-competent Arabidopsis lines, with new Plastid transformation vectors and a protocol for measuring Plastid transformation efficiency, will advance the engineering of the Plastid Genome in Arabidopsis.
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Next generation synthetic vectors for transformation of the Plastid Genome of higher plants
Plant Molecular Biology, 2009Co-Authors: Sugey Ramona Sinagawa-garcía, Tarinee Tungsuchat-huang, Octavio Paredes-lópez, Pál MaligaAbstract:Plastid transformation vectors are E. coli plasmids carrying a Plastid marker gene for selection, adjacent cloning sites and flanking Plastid DNA to target insertions in the Plastid Genome by homologous recombination. We report here on a family of next generation Plastid vectors carrying synthetic DNA vector arms targeting insertions in the rbcL-accD intergenic region of the tobacco ( Nicotiana tabacum ) Plastid Genome. The pSS22 plasmid carries only synthetic vector arms from which the undesirable restriction sites have been removed by point mutations. The pSS24 vector carries a c-Myc tagged spectinomycin resistance ( aadA ) marker gene whereas in vector pSS30 aadA is flanked with loxP sequences for post-transformation marker excision. The synthetic vectors will enable direct manipulation of passenger genes in the transformation vector targeting insertions in the rbcL-accD intergenic region that contains many commonly used restriction sites.
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Identification of functional lox sites in the Plastid Genome
Plant Journal, 2003Co-Authors: Sylvie Corneille, Kerry Lutz, Arun K. Azhagiri, Pál MaligaAbstract:Summary Our objective was to test whether or not cyclization recombination (CRE), the P1 phage site-specific recombinase, induces Genome rearrangements in Plastids. Testing was carried out in tobacco plants in which a DNA sequence, located between two inversely oriented locus of X-over of P1 (loxP) sites, underwent repeated cycles of inversions as a means of monitoring CRE activity. We report here that CRE mediates deletions between loxP sites and Plastid DNA sequences in the 3′rps12 gene leader (lox-rps12) or in the psbA promoter core (lox-psbA). We also observed deletions between two directly oriented lox-psbA sites, but not between lox-rps12 sites. Deletion via duplicated rRNA operon promoter (Prrn) sequences was also frequent in CRE-active plants. However, CRE-mediated recombination is probably not directly involved, as no recombination junction between loxP and Prrn could be observed. Tobacco plants carrying deleted Genomes as a minor fraction of the Plastid Genome population were fertile and phenotypically normal, suggesting that the absence of deleted Genome segments was compensated by gene expression from wild-type copies. The deleted Plastid Genomes disappeared in the seed progeny lacking CRE. Observed Plastid Genome rearrangements are specific to engineered Plastid Genomes, which contain at least one loxP site or duplicated psbA promoter sequences. The wild-type Plastid Genome is expected to be stable, even if CRE is present in the Plastid.
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engineering the Plastid Genome of higher plants
Current Opinion in Plant Biology, 2002Co-Authors: Pál MaligaAbstract:The Plastid Genome of higher plants is an attractive target for engineering because it provides readily obtainable high protein levels, the feasibility of expressing multiple proteins from polycistronic mRNAs and gene containment through the lack of pollen transmission. A chloroplast-based expression system that is suitable for the commercial production of recombinant proteins in tobacco leaves has been developed recently. This expression system includes vectors, expression cassettes and site-specific recombinases for the selective elimination of marker genes. Progress in expressing proteins that are biomedically relevant, in engineering metabolic pathways, and in manipulating photosynthesis and agronomic traits is discussed, as are the problems of implementing the technology in crops.
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efficient elimination of selectable marker genes from the Plastid Genome by the cre lox site specific recombination system
Plant Journal, 2001Co-Authors: Sylvie Corneille, Kerry Lutz, Zora Svab, Pál MaligaAbstract:Summary Incorporation of a selectable marker gene during transformation is essential to obtain transformed Plastids. However, once transformation is accomplished, having the marker gene becomes undesirable. Here we report on adapting the P1 bacteriophage CRE-lox site-specific recombination system for the elimination of marker genes from the Plastid Genome. The system was tested by the elimination of a negative selectable marker, codA, which is flanked by two directly oriented lox sites (>codA>). Highly efficient elimination of >codA> was triggered by introduction of a nuclear-encoded Plastid-targeted CRE by Agrobacterium transformation or via pollen. Excision of >codA> in tissue culture cells was frequently accompanied by a large deletion of a Plastid Genome segment which includes the tRNA-ValUAC gene. However, the large deletions were absent when cre was introduced by pollination. Thus pollination is our preferred protocol for the introduction of cre. Removal of the >codA> coding region occurred at a dramatic speed, in striking contrast to the slow and gradual build-up of transgenic copies during Plastid transformation. The nuclear cre gene could subsequently be removed by segregation in the seed progeny. The modified CRE-lox system described here will be a highly efficient tool to obtain marker-free transplastomic plants.
Tsuneyoshi Kuroiwa - One of the best experts on this subject based on the ideXlab platform.
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Complete sequence and analysis of the Plastid Genome of the unicellular red alga Cyanidioschyzon merolae.
DNA Research, 2003Co-Authors: Niji Ohta, Motomichi Matsuzaki, Osami Misumi, Shin-ya Miyagishima, Hisayoshi Nozaki, Kan Tanaka, Tadasu Shin-i, Yuji Kohara, Tsuneyoshi KuroiwaAbstract:The complete nucleotide sequence of the Plastid Genome of the unicellular primitive red alga Cyanidioschyzon merolae 10D (Cyanidiophyceae) was determined. The Genome is a circular DNA composed of 149,987 bp with no inverted repeats. The G + C content of this Plastid Genome is 37.6%. The C. merolae Plastid Genome contains 243 genes, which are distributed on both strands and consist of 36 RNA genes (3 rRNAs, 31 tRNAs, tmRNA, and a ribonuclease P RNA component) and 207 protein genes, including unidentified open reading frames. The striking feature of this Genome is the high degree of gene compaction; it has very short intergenic distances (approximately 40% of the protein genes were overlapped) and no genes have introns. This Genome encodes several genes that are rarely found in other Plastid Genomes. A gene encoding a subunit of sulfate transporter (cysW) is the first to be identified in a Plastid Genome. The cysT and cysW genes are located in the C. merolae Plastid Genome in series, and they probably function together with other nuclear-encoded components of the sulfate transport system. Our phylogenetic results suggest that the Cyanidiophyceae, including C. merolae, are a basal clade within the red lineage Plastids.
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Physical map of the Plastid Genome of the unicellular red alga Cyanidium caldarium strain RK-1.
Current Genetics, 1994Co-Authors: Niji Ohta, Shigeyuki Kawano, Tsuneyoshi KuroiwaAbstract:The physical map of the Plastid Genome of the unicellular red alga Cyanidium caldarium strain RK-1 was constructed. The 150-kbp Genome was circular and had an inverted repeat region (IR) which contained the genes for 16 s and 23 s ribosomal RNAs, as is usually seen in most Plastid Genomes. Since C. caldarium is a very “primitive” alga, the results suggest that the ancestral cyanobacteria lost most of its Genome as an endosymbiont comparatively early in the process of Plastid formation. After that, several genes seem to have been lost from Plastid Genomes, step by step, during the course of evolution.
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The trpA gene on the Plastid Genome of Cyanidium caldarium strain RK-1.
Current Genetics, 1994Co-Authors: Niji Ohta, Shigeyuki Kawano, Naoki Sato, Tsuneyoshi KuroiwaAbstract:The trpA gene (for the α subunit of tryptophan synthase) was found on the Plastid Genome of the “primitive” unicellular red alga Cyanidium caldarium strain RK-1. This is the first example of an actively-transcribed gene for tryptophan synthase encoded on a Plastid Genome. In contrast to trpA, trpB (the gene for the β subunit of tryptophan synthase) was encoded in the cell nucleus. Considering the primitive characteristics of C. caldarium, trpB must have been lost from the Plastid Genome before trpA.
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Plastid Genome of Cyanidium caldarium Strain RK-1 Encodes trpA
Cytologia, 1993Co-Authors: Niji Ohta, Shigeyuki Kawano, Tsuneyoshi KuroiwaAbstract:We examined the organization of organelle DNA in the two algae, Cyanidium caldarium RK-1 and C. caldrium M-8 with epifluorescence microscopy and molecular-biological techniques. The Plastid nucleus (pt-nucleus, a complex of DNA and proteins) is located in the central area of the Plastid in C. caldarium RK-1, while the ring-shaped pt-nucleus is located at the periphery of the petal-like Plastid in C. caldarium M-8. The results suggest that C. caladarium RK-1 markedly differs from C. caldarium M-8 in an evolutionary tree.To confirm the result, we examined the fragment that contained rbcL. The trpA (the gene for the α subunit of the tryptophan synthase), which was located on the vicinity of the rbcL, was found on the Plastid Genome of the “primitive” unicellular red alga, C. caldarium RK-1, while the gene could not be found on the Plastid Genome of the C. calardium M-8 (Galdieria sulphuraria). This is the first example of typtophan synthase encoded on the Plastid Genome. The results suggest that the trpA gene may have relocated from the Plastid Genome to the cellnuclear Genome for longer ago than the genes that have been considered to date to have been lost from Plastid Genomes in the advanced members of plants.
Niji Ohta - One of the best experts on this subject based on the ideXlab platform.
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Complete sequence and analysis of the Plastid Genome of the unicellular red alga Cyanidioschyzon merolae.
DNA Research, 2003Co-Authors: Niji Ohta, Motomichi Matsuzaki, Osami Misumi, Shin-ya Miyagishima, Hisayoshi Nozaki, Kan Tanaka, Tadasu Shin-i, Yuji Kohara, Tsuneyoshi KuroiwaAbstract:The complete nucleotide sequence of the Plastid Genome of the unicellular primitive red alga Cyanidioschyzon merolae 10D (Cyanidiophyceae) was determined. The Genome is a circular DNA composed of 149,987 bp with no inverted repeats. The G + C content of this Plastid Genome is 37.6%. The C. merolae Plastid Genome contains 243 genes, which are distributed on both strands and consist of 36 RNA genes (3 rRNAs, 31 tRNAs, tmRNA, and a ribonuclease P RNA component) and 207 protein genes, including unidentified open reading frames. The striking feature of this Genome is the high degree of gene compaction; it has very short intergenic distances (approximately 40% of the protein genes were overlapped) and no genes have introns. This Genome encodes several genes that are rarely found in other Plastid Genomes. A gene encoding a subunit of sulfate transporter (cysW) is the first to be identified in a Plastid Genome. The cysT and cysW genes are located in the C. merolae Plastid Genome in series, and they probably function together with other nuclear-encoded components of the sulfate transport system. Our phylogenetic results suggest that the Cyanidiophyceae, including C. merolae, are a basal clade within the red lineage Plastids.
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Physical map of the Plastid Genome of the unicellular red alga Cyanidium caldarium strain RK-1.
Current Genetics, 1994Co-Authors: Niji Ohta, Shigeyuki Kawano, Tsuneyoshi KuroiwaAbstract:The physical map of the Plastid Genome of the unicellular red alga Cyanidium caldarium strain RK-1 was constructed. The 150-kbp Genome was circular and had an inverted repeat region (IR) which contained the genes for 16 s and 23 s ribosomal RNAs, as is usually seen in most Plastid Genomes. Since C. caldarium is a very “primitive” alga, the results suggest that the ancestral cyanobacteria lost most of its Genome as an endosymbiont comparatively early in the process of Plastid formation. After that, several genes seem to have been lost from Plastid Genomes, step by step, during the course of evolution.
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The trpA gene on the Plastid Genome of Cyanidium caldarium strain RK-1.
Current Genetics, 1994Co-Authors: Niji Ohta, Shigeyuki Kawano, Naoki Sato, Tsuneyoshi KuroiwaAbstract:The trpA gene (for the α subunit of tryptophan synthase) was found on the Plastid Genome of the “primitive” unicellular red alga Cyanidium caldarium strain RK-1. This is the first example of an actively-transcribed gene for tryptophan synthase encoded on a Plastid Genome. In contrast to trpA, trpB (the gene for the β subunit of tryptophan synthase) was encoded in the cell nucleus. Considering the primitive characteristics of C. caldarium, trpB must have been lost from the Plastid Genome before trpA.
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Plastid Genome of Cyanidium caldarium Strain RK-1 Encodes trpA
Cytologia, 1993Co-Authors: Niji Ohta, Shigeyuki Kawano, Tsuneyoshi KuroiwaAbstract:We examined the organization of organelle DNA in the two algae, Cyanidium caldarium RK-1 and C. caldrium M-8 with epifluorescence microscopy and molecular-biological techniques. The Plastid nucleus (pt-nucleus, a complex of DNA and proteins) is located in the central area of the Plastid in C. caldarium RK-1, while the ring-shaped pt-nucleus is located at the periphery of the petal-like Plastid in C. caldarium M-8. The results suggest that C. caladarium RK-1 markedly differs from C. caldarium M-8 in an evolutionary tree.To confirm the result, we examined the fragment that contained rbcL. The trpA (the gene for the α subunit of the tryptophan synthase), which was located on the vicinity of the rbcL, was found on the Plastid Genome of the “primitive” unicellular red alga, C. caldarium RK-1, while the gene could not be found on the Plastid Genome of the C. calardium M-8 (Galdieria sulphuraria). This is the first example of typtophan synthase encoded on the Plastid Genome. The results suggest that the trpA gene may have relocated from the Plastid Genome to the cellnuclear Genome for longer ago than the genes that have been considered to date to have been lost from Plastid Genomes in the advanced members of plants.
Jeffrey D Palmer - One of the best experts on this subject based on the ideXlab platform.
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function and evolution of a minimal Plastid Genome from a nonphotosynthetic parasitic plant
Proceedings of the National Academy of Sciences of the United States of America, 1992Co-Authors: Kenneth H. Wolfe, Clifford W. Morden, Jeffrey D PalmerAbstract:Abstract Complete nucleotide sequencing shows that the Plastid Genome of Epifagus virginiana, a nonphotosynthetic parasitic flowering plant, lacks all genes for photosynthesis and chlororespiration found in chloroplast Genomes of green plants. The 70,028-base-pair Genome contains only 42 genes, at least 38 of which specify components of the gene-expression apparatus of the Plastid. Moreover, all chloroplast-encoded RNA polymerase genes and many tRNA and ribosomal protein genes have been lost. Since the Genome is functional, nuclear gene products must compensate for some gene losses by means of previously unsuspected import mechanisms that may operate in all Plastids. At least one of the four unassigned protein genes in Epifagus Plastid DNA must have a nongenetic and nonbioenergetic function and, thereby, serve as the reason for the maintenance of an active Genome. Many small insertions in the Epifagus Plastid Genome create tandem duplications and presumably arose by slippage mispairing during DNA replication. The extensive reduction in Genome size in Epifagus reflects an intensification of the same processes of length mutation that govern the amount of noncoding DNA in chloroplast Genomes. Remarkably, this massive pruning occurred with a virtual absence of gene order change.
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Ins and outs of Plastid Genome evolution.
Current Opinion in Genetics & Development, 1991Co-Authors: Kenneth H. Wolfe, Clifford W. Morden, Jeffrey D PalmerAbstract:Recent findings have established cracks in the straight-laced image of the Plastid Genome as a molecule whose sole function is photosynthesis and whose gene content is highly conserved. Genes for numerous non-photosynthetic functions have been identified. Algal Plastid Genomes contain many genes with no homologs in angiosperms, and the recent transfer of genes from the Plastid to the nuclear Genome has been described. Wholesale abandonment of genes encoding photosynthetic and gene-expression functions has occurred in the Plastid Genomes of a non-green plant and alga. The origins of Plastid DNA, its use in phylogenetic studies, and the origins of Plastid introns are also reviewed.
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loss of photosynthetic and chlororespiratory genes from the Plastid Genome of a parasitic flowering plant
Nature, 1990Co-Authors: Claude W. Depamphilis, Jeffrey D PalmerAbstract:Photosynthesis is the hallmark of plant life and is the only Plastid metabolic process known to be controlled by Plastid genes. The complete loss of photosynthetic ability, however, has occurred on several independent occasions in parasitic flowering plants. Some of these plants are known to lack chlorophyll and certain photosynthetic enzymes, but it is not known to what extent changes have occurred in the genes encoding the photosynthetic apparatus or whether the plants even maintain a Plastid Genome. Here we report that the nonphotosynthetic root parasite Epifagus virginiana has a Plastid chromosome only 71 kilobases in size, far smaller than any previously characterized land plant Plastid Genome. The Epifagus Plastid Genome has lost most, if not all, of the 30 or more chloroplast genes for photosynthesis and most of a large family of Plastid genes, the ndh genes, whose products may be involved in a Plastid respiratory chain. The extensive changes in Epifagus Plastid gene content must have occurred in a relatively short time (5-50 x 10(6) yr), because Striga asiatica, a related photosynthetic parasite, has a typical complement of chloroplast genes for photosynthesis and chlororespiration. The Plastid Genome of Epifagus has retained transcribed ribosomal RNA and ribosomal protein genes, suggesting that it expresses one or more gene products for Plastid functions not related to photosynthesis.