Reappraisal of the Genetic Map of Chlamydomonas reinhardtii

Dutcher, Susan K.; Power, Joy M.; Galloway, Ruth E.; Porter, Mary E.

doi:10.1093/oxfordjournals.jhered.a111089

Cited by 24 publications

(14 citation statements)

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“…The Chlamydomonas nic15-1 mutant is tightly linked to MAA1 on LGXII/XIII [22]. The nic15-1 strain (See Materials and Methods) contains a single nucleotide change C 1376 T that predicts a S 459 F change in the predicted protein (Figure 3A).…”

Section: Resultsmentioning

confidence: 99%

“…We tested whether the remaining NIC loci encode the enzymes of the de novo aspartate NAD + synthesis pathway. The nic mutant loci define six different loci and map to six different linkage groups (LG) [19]: NIC1 maps to LG XV; NIC2 maps to LG II; NIC7 maps to LG VI; NIC11 maps to LG IV; NIC13 maps to LG X; and NIC15 maps to LG XII/XIII [[20], [ 22]–[25]; see Materials and Methods for linkage group to chromosome translation]. In our study, phenotypic characterization and genetic crosses of nic11 strains obtained from the Chlamydomonas Center indicate that the Nic − phenotype of these nic11 strains (sensitivity to 3-AP or a growth defect on medium lacking NAM) can no longer be scored.…”

Section: Introductionmentioning

confidence: 99%

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Synthesizing and Salvaging NAD+: Lessons Learned from Chlamydomonas reinhardtii

2010

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The essential coenzyme nicotinamide adenine dinucleotide (NAD+) plays important roles in metabolic reactions and cell regulation in all organisms. Bacteria, fungi, plants, and animals use different pathways to synthesize NAD+. Our molecular and genetic data demonstrate that in the unicellular green alga Chlamydomonas NAD+ is synthesized from aspartate (de novo synthesis), as in plants, or nicotinamide, as in mammals (salvage synthesis). The de novo pathway requires five different enzymes: L-aspartate oxidase (ASO), quinolinate synthetase (QS), quinolate phosphoribosyltransferase (QPT), nicotinate/nicotinamide mononucleotide adenylyltransferase (NMNAT), and NAD+ synthetase (NS). Sequence similarity searches, gene isolation and sequencing of mutant loci indicate that mutations in each enzyme result in a nicotinamide-requiring mutant phenotype in the previously isolated nic mutants. We rescued the mutant phenotype by the introduction of BAC DNA (nic2-1 and nic13-1) or plasmids with cloned genes (nic1-1 and nic15-1) into the mutants. NMNAT, which is also in the de novo pathway, and nicotinamide phosphoribosyltransferase (NAMPT) constitute the nicotinamide-dependent salvage pathway. A mutation in NAMPT (npt1-1) has no obvious growth defect and is not nicotinamide-dependent. However, double mutant strains with the npt1-1 mutation and any of the nic mutations are inviable. When the de novo pathway is inactive, the salvage pathway is essential to Chlamydomonas for the synthesis of NAD+. A homolog of the human SIRT6-like gene, SRT2, is upregulated in the NS mutant, which shows a longer vegetative life span than wild-type cells. Our results suggest that Chlamydomonas is an excellent model system to study NAD+ metabolism and cell longevity.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synthesizing and Salvaging NAD+: Lessons Learned from Chlamydomonas reinhardtii

2010

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“…Gametes can be crossed to yield diploid zygotes that sporulate to produce four products of meiosis, allowing routine tetrad analysis. Over the past 50 years, hundreds of mutations have been isolated; more than 200 genetic loci have been mapped to 17 linkage groups (28,29,45,46,52). Mutations induced by chemical or UV mutagenesis have been supplemented recently by mutations induced by transposition of one of several transposable element families in the genome (17,34,130,133) or by insertional mutagenesis (13,101,149).…”

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confidence: 99%

Molecular Map of theChlamydomonas reinhardtiiNuclear Genome

et al. 2003

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We have prepared a molecular map of the Chlamydomonas reinhardtii genome anchored to the genetic map. The map consists of 264 markers, including sequence-tagged sites (STS), scored by use of PCR and agarose gel electrophoresis, and restriction fragment length polymorphism markers, scored by use of Southern blot hybridization. All molecular markers tested map to one of the 17 known linkage groups of C. reinhardtii. The map covers approximately 1,000 centimorgans (cM). Any position on the C. reinhardtii genetic map is, on average, within 2 cM of a mapped molecular marker. This molecular map, in combination with the ongoing mapping of bacterial artificial chromosome (BAC) clones and the forthcoming sequence of the C. reinhardtii nuclear genome, should greatly facilitate isolation of genes of interest by using positional cloning methods. In addition, the presence of easily assayed STS markers on each arm of each linkage group should be very useful in mapping new mutations in preparation for positional cloning.Studies using the unicellular eukaryotic alga Chlamydomonas reinhardtii have yielded important insights into many cellular processes including photosynthesis (45, 123), flagellar assembly and motility (24,28,86,112,114,124,137,140), basal body assembly and positioning (115), gametogenesis and fertilization (35,42,167), DNA repair (109), phototaxis (49, 139), cell wall assembly (1), circadian rhythms (91, 162), and the regulation of metabolic pathways (3,14,31,50).A major strength of C. reinhardtii as an experimental system is its usefulness for genetic experiments (45,47,74). Vegetative cells are haploid, facilitating the analysis of mutant phenotypes, but stable diploid strains can be easily produced for dominance and complementation tests. Gametes can be crossed to yield diploid zygotes that sporulate to produce four products of meiosis, allowing routine tetrad analysis. Over the past 50 years, hundreds of mutations have been isolated; more than 200 genetic loci have been mapped to 17 linkage groups (28,29,45,46,52). Mutations induced by chemical or UV mutagenesis have been supplemented recently by mutations induced by transposition of one of several transposable element families in the genome (17,34,130,133) or by insertional mutagenesis (13,101,149).Insertional mutagenesis has become the favored method for generating mutations since the development of procedures for efficient transformation of the nuclear genome (59, 132). Upon transformation, plasmid DNA inserts in random positions into the nuclear genome, facilitating cloning of affected genes by using the transforming plasmid as a hybridization probe. This method of gene tagging has led to the isolation of numerous genes identified by mutation over the past several years. Despite its usefulness, the insertional-mutagenesis approach has drawbacks, including the inability to clone essential genes, difficulty in analyzing the large deletions that occur in some cases, and a limitation in the types of phenotypes that can be found by using a method that genera...

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“…gave close to 50% recombination, which indicates nonlinkage (Table 1). However, data from crosses between metl and each of the three markers, cry-2, maa-4, and agg-1 revealed a map distance of less than 48%, and all of these three markers had been previously mapped to linkage group XIV (Harris 1989, Dutcher et al 1991 …”

Section: Terminal Phenotypementioning

confidence: 99%

Themet1 mutation inChlamydomonas reinhardtii causes arrest at mitotic metaphase with persisting p34cdc2-like H1 histone kinase activity that can promote mitosis when injected into higher-plant cells

Hepler

John

1997

Protoplasma

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Summary.The metl mutation in Chlamydomonas reinhardtii causes metaphase arrest. Arrested cells have disassembled cortical microtubules, a fully assembled spindle, condensed and aligned metaphase chromosomes and abundant mitotic phosphoproteins recognised by MPM-2 antibody in the nuclear region. Protein purified by affinity for the mitotic protein p 13 s~cl contains p34Cd~2-1ike H 1 histone kinase activity at times when control cells have inactivated this enzyme. The active enzyme, when microinjected into Tradescantia stamen hair cells, accelerated progress through prophase to normal completion of mitosis, indicating that the mutation did not disable the mitotic Cdc2 protein kinase enzyme complex. The mutation prevented the normal lowering of this kinase activity that accompanies anaphase. A defect at time of mitosis rather than earlier in the cycle was indicated by temperature shifting of synchronous cells, which identified the earliest faulty progress as occurring near the beginning of mitosis and the time at which the essential function is completed near the end of mitosis. The metl gene mapped approximately 33 cM from ery-2 and extended the known limits of the linkage group XIV.

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Reappraisal of the Genetic Map of Chlamydomonas reinhardtii

Cited by 24 publications

References 1 publication

Synthesizing and Salvaging NAD+: Lessons Learned from Chlamydomonas reinhardtii

Synthesizing and Salvaging NAD+: Lessons Learned from Chlamydomonas reinhardtii

Molecular Map of theChlamydomonas reinhardtiiNuclear Genome

Themet1 mutation inChlamydomonas reinhardtii causes arrest at mitotic metaphase with persisting p34cdc2-like H1 histone kinase activity that can promote mitosis when injected into higher-plant cells

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