Conservation and degradation of cytoplasmic and chloroplast ribosomes in Chlamydomonas reinhardtii

Siersma, Peter; Chiang, Kwen‐Sheng

doi:10.1016/0022-2836(71)90239-7

Cited by 82 publications

(47 citation statements)

References 15 publications

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“…For standardization, equal amounts of RNA were loaded and the 18S rRNA abundance was examined. Although C. reinhardtii ribosomes turn over following N deprivation (Siersma and Chiang, 1971;Martin et al, 1976), their abundance drops no lower than 50% (see below). AMT4 mRNA was absent from the uninduced cells and present at a high level in N-limited or N-deprived cells under the conditions tested.…”

Section: Defining Conditions For N Deprivation Of C Reinhardtiimentioning

confidence: 99%

“…Decades ago, N deprivation of C. reinhardtii was found to result in degradation and resynthesis of both cytoplasmic and chloroplast ribosomes (Siersma and Chiang, 1971;Martin et al, 1976). Both the rRNA and proteins of the ribosomes were turned over under the conditions of N deprivation that also induce gamete differentiation.…”

Section: Effects On Genes Of N Metabolism and Protein Biosynthesismentioning

confidence: 99%

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Changes in Transcript Abundance in Chlamydomonas reinhardtii following Nitrogen Deprivation Predict Diversion of Metabolism

et al. 2010

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Like many microalgae, Chlamydomonas reinhardtii forms lipid droplets rich in triacylglycerols when nutrient deprived. To begin studying the mechanisms underlying this process, nitrogen (N) deprivation was used to induce triacylglycerol accumulation and changes in developmental programs such as gametogenesis. Comparative global analysis of transcripts under induced and noninduced conditions was applied as a first approach to studying molecular changes that promote or accompany triacylglycerol accumulation in cells encountering a new nutrient environment. Towards this goal, high-throughput sequencing technology was employed to generate large numbers of expressed sequence tags of eight biologically independent libraries, four for each condition, N replete and N deprived, allowing a statistically sound comparison of expression levels under the two tested conditions. As expected, N deprivation activated a subset of control genes involved in gametogenesis while down-regulating protein biosynthesis. Genes for components of photosynthesis were also down-regulated, with the exception of the PSBS gene. N deprivation led to a marked redirection of metabolism: the primary carbon source, acetate, was no longer converted to cell building blocks by the glyoxylate cycle and gluconeogenesis but funneled directly into fatty acid biosynthesis. Additional fatty acids may be produced by membrane remodeling, a process that is suggested by the changes observed in transcript abundance of putative lipase genes. Inferences on metabolism based on transcriptional analysis are indirect, but biochemical experiments supported some of these deductions. The data provided here represent a rich source for the exploration of the mechanism of oil accumulation in microalgae.

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Section: Defining Conditions For N Deprivation Of C Reinhardtiimentioning

confidence: 99%

Section: Effects On Genes Of N Metabolism and Protein Biosynthesismentioning

confidence: 99%

Changes in Transcript Abundance in Chlamydomonas reinhardtii following Nitrogen Deprivation Predict Diversion of Metabolism

et al. 2010

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“…The most prominent changes at the molecular level have been demonstrated for the ribosomes. Cytoplasmic and chloroplast ribosomes decrease in number (7,8,13) and new ribosomes appear that exhibit decreased translational accuracy (2), altered susceptibility to antibiotics (9), and ribosomal proteins with different electrophoretic mobilities (9). Morphologically, the acquisition of two new organelles, a mating structure and a special type of Golgi-derived vesicle are most prominent (3, 7).…”

Section: Introductionmentioning

confidence: 99%

Gametic Differentiation of Chlamydomonas reinhardtii

Beck

Acker²

1992

Plant Physiol.

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Gametic differentiation of the unicellular green alga Chiamydomonas reinhardtii proceeds in two steps controlled by the extrinsic signals nitrogen deficiency and light. Nitrogen deprivation induces the differentiation of vegetative cells to sexually immature pregametes. A light signal is required to convert the pregametes to gametes. Both signals are also required for the maintenance of mating competence. Two converging signal transduction chains are proposed to control gamete formation. For the differentiation of pregametes to gametes, a fluence ratedependent reaction, requiring continuous irradiation, is suggested by photobiological experiments.By gametic differentiation, Chlamydomonas reinhardtii vegetative cells are transformed into mating-competent cells. This differentiation has been shown to be associated with changes in the cell's biochemistry and subcellular morphology. The most prominent changes at the molecular level have been demonstrated for the ribosomes. Cytoplasmic and chloroplast ribosomes decrease in number (7,8,13) and new ribosomes appear that exhibit decreased translational accuracy (2), altered susceptibility to antibiotics (9), and ribosomal proteins with different electrophoretic mobilities (9). Morphologically, the acquisition of two new organelles, a mating structure and a special type of Golgi-derived vesicle are most prominent (3, 7). These and other changes, e.g. the appearance of sexual agglutinins (1,11,19) and the synthesis of gametic autolysin (12,16) suggest that gametic differentiation is based on changes in the pattern of gene expression. Characteristic differences in the rates of synthesis of individual proteins (15)

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“…In addition, cells were allowed to differentiate into gametes after transformation but before selection was applied. During the differentiation of vegetative cells into gametes induced by nitrogen starvation, Chlamydomonas cells degrade up to 90% of their ribosomal protein (44). RNA blots from differentiating and dedifferentiating cells probed with the CRY1 cDNA clone showed that the level of the CRY1 transcript slowly decreased about twofold over 24 h after the removal of nitrogen, and the transcript level increased about twofold within 1 h after the readdition of ammonium to the medium (42).…”

Section: Resultsmentioning

confidence: 99%

The CRY1 gene in Chlamydomonas reinhardtii: structure and use as a dominant selectable marker for nuclear transformation.

Nelson¹,

Savereide²,

Lefebvre³

1994

Mol. Cell. Biol.

135

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We have cloned and sequenced the CRY] gene, encoding ribosomal protein S14 in Chkimydomonas reinhardtii, and found that it is highly similar to S14/rp59 proteins from other organisms, including mammals, Drosophila melanogaster, and Saccharomyces cerevisiae. We isolated a mutant strain resistant to the eukaryotic translational inhibitors cryptopleurine and emetine in which the resistance was due to a missense mutation (CRY)-I) in the CRY) gene; resistance was dominant in heterozygous stable diploids. Cotransformation experiments using the CRY)-) gene and the gene for nitrate reductase (NIT)) produced a low level of resistance to cryptopleurine and emetine. Resistance levels were increased when the CRY)-) gene was placed under the control of a constitutive promoter from the ribulose bisphosphate carboxylase/oxygenase small subunit 2 (RBCS2) gene. We also found that the 5' untranslated region of the CRY) gene was required for expression of the CRY)-) transgene. Direct selection of emetine-resistant transformants was possible when transformed cells were first induced to differentiate into gametes by nitrogen starvation and then allowed to dedifferentiate back to vegetative cells before emetine selection was applied. With this transformation protocol, the RBCS2/CRYI-I dominant selectable marker gene is a powerful tool for many molecular genetic applications in C. reinhardtii.Chlamydomonas reinhardtii has been an excellent model organism for many areas of research, particularly for the study of flagellar structure and function (25), chloroplast function (1), and cell-cell interactions during mating (9). The development of reliable nuclear transformation procedures (18) opened the Chlamydomonas field to techniques such as insertional mutagenesis (47) and homologous recombination (46). One limitation, however, has been a shortage of selectable marker genes. Heterologous genes are very poorly expressed when transformed into C. reinhardtii. A few reports of selection using heterologous genes have appeared (11,13,38), although no heterologous gene has allowed efficient recovery of transformants. Several C. reinhardtii genes corresponding to auxotrophic mutants, including the genes for nitrate reductase (NITJ) (7,19), argininosuccinate lyase (ARG7) (4), and oxygen-evolving enhancer protein 1 (OEEI) (29), have been cloned and characterized for use as efficient transformation markers. Dominant C. reinhardtii mutations that confer resistance to herbicides and other drugs are promising candidates for providing selectable marker genes. We identified a mutation in the ribosomal protein S14 gene of C. reinhardtii that produced resistance to the eukaryotic translation inhibitors cryptopleurine and emetine, providing an easily clonable selectable marker gene. Mutations in the ribosomal protein S14/rp59 genes of Cricetulus griseus (Chinese hamster ovary cells) and Saccharomyces cerevisiae are responsible for resistance to emetine and cryptopleurine, respectively (31, 37), and these and other S14 genes have been sequenced and found to...

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Conservation and degradation of cytoplasmic and chloroplast ribosomes in Chlamydomonas reinhardtii

Cited by 82 publications

References 15 publications

Changes in Transcript Abundance in Chlamydomonas reinhardtii following Nitrogen Deprivation Predict Diversion of Metabolism

Changes in Transcript Abundance in Chlamydomonas reinhardtii following Nitrogen Deprivation Predict Diversion of Metabolism

Gametic Differentiation of Chlamydomonas reinhardtii

The CRY1 gene in Chlamydomonas reinhardtii: structure and use as a dominant selectable marker for nuclear transformation.

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