The
 ARG9
 Gene Encodes the Plastid-Resident
 N
 -Acetyl Ornithine Aminotransferase in the Green Alga
 Chlamydomonas reinhardtii

Remacle, Claire; Cline, Sara; Boutaffala, Layla; Gabilly, Stéphane T.; Larosa, Véronique; Barbieri, Marcello; Coosemans, Nadine; Hamel, Patrice

doi:10.1128/ec.00108-09

Cited by 32 publications

(14 citation statements)

References 9 publications

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“…The NAOAT encoding gene Arg9 was identified and characterized in the green alga Chlamydomonas reinhardtii ( Remacle et al, 2009 ). Plastidial localization of NAOAT was demonstrated by complementation studies as well as immunoblot analysis.…”

Section: Cyclic and Linear Pathways For Ornithine Synthesismentioning

confidence: 99%

Physiological implications of arginine metabolism in plants

et al. 2015

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Nitrogen is a limiting resource for plant growth in most terrestrial habitats since large amounts of nitrogen are needed to synthesize nucleic acids and proteins. Among the 21 proteinogenic amino acids, arginine has the highest nitrogen to carbon ratio, which makes it especially suitable as a storage form of organic nitrogen. Synthesis in chloroplasts via ornithine is apparently the only operational pathway to provide arginine in plants, and the rate of arginine synthesis is tightly regulated by various feedback mechanisms in accordance with the overall nutritional status. While several steps of arginine biosynthesis still remain poorly characterized in plants, much wider attention has been paid to inter- and intracellular arginine transport as well as arginine-derived metabolites. A role of arginine as alternative source besides glutamate for proline biosynthesis is still discussed controversially and may be prevented by differential subcellular localization of enzymes. Apparently, arginine is a precursor for nitric oxide (NO), although the molecular mechanism of NO production from arginine remains unclear in higher plants. In contrast, conversion of arginine to polyamines is well documented, and in several plant species also ornithine can serve as a precursor for polyamines. Both NO and polyamines play crucial roles in regulating developmental processes as well as responses to biotic and abiotic stress. It is thus conceivable that arginine catabolism serves on the one hand to mobilize nitrogen storages, while on the other hand it may be used to fine-tune development and defense mechanisms against stress. This review summarizes the recent advances in our knowledge about arginine metabolism, with a special focus on the model plant Arabidopsis thaliana, and pinpoints still unresolved critical questions.

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Section: Cyclic and Linear Pathways For Ornithine Synthesismentioning

confidence: 99%

Physiological implications of arginine metabolism in plants

et al. 2015

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“…The foreign ARG9 gene, now encoded by the chloroplast genome, was able to rescue the auxotrophic phenotype and restore arginine synthesis. This elegant approach created a metabolic selection system for chloroplast transformation in Chlamydomonas (Remacle et al, 2009 ).…”

Section: Chloroplast Transformation Systemsmentioning

confidence: 99%

Transgene Expression in Microalgae—From Tools to Applications

2016

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Microalgae comprise a biodiverse group of photosynthetic organisms that reside in water sources and sediments. The green microalgae Chlamydomonas reinhardtii was adopted as a useful model organism for studying various physiological systems. Its ability to grow under both photosynthetic and heterotrophic conditions allows efficient growth of non-photosynthetic mutants, making Chlamydomonas a useful genetic tool to study photosynthesis. In addition, this green alga can grow as haploid or diploid cells, similar to yeast, providing a powerful genetic system. As a result, easy and efficient transformation systems have been developed for Chlamydomonas, targeting both the chloroplast and nuclear genomes. Since microalgae comprise a rich repertoire of species that offer variable advantages for biotech and biomed industries, gene transfer technologies were further developed for many microalgae to allow for the expression of foreign proteins of interest. Expressing foreign genes in the chloroplast enables the targeting of foreign DNA to specific sites by homologous recombination. Chloroplast transformation also allows for the introduction of genes encoding several enzymes from a complex pathway, possibly as an operon. Expressing foreign proteins in the chloroplast can also be achieved by introducing the target gene into the nuclear genome, with the protein product bearing a targeting signal that directs import of the transgene-product into the chloroplast, like other endogenous chloroplast proteins. Integration of foreign genes into the nuclear genome is mostly random, resulting in large variability between different clones, such that extensive screening is required. The use of different selection modalities is also described, with special emphasis on the use of herbicides and metabolic markers which are considered to be friendly to the environment, as compared to drug-resistance genes that are commonly used. Finally, despite the development of a wide range of transformation tools and approaches, expression of foreign genes in microalgae suffers from low efficiency. Thus, novel tools have appeared in recent years to deal with this problem. Finally, while C. reinhardtii was traditionally used as a model organism for the development of transformation systems and their subsequent improvement, similar technologies can be adapted for other microalgae that may have higher biotechnological value.

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“…In Chlamydomonas, mutations in the ARG9 gene cause arginine auxotrophy because of a defect in N ‐acetyl ornithine aminotransferase activity. Using an arg9 mutant host, the wild‐type ARG9 gene can be used as a marker for chloroplast transformation (Remacle et al. , 2009).…”

Section: Selectable Markers For Plastid Transformationmentioning

confidence: 99%

“…In Chlamydomonas, mutations in the ARG9 gene cause arginine auxotrophy because of a defect in N-acetyl ornithine aminotransferase activity. Using an arg9 mutant host, the wild-type ARG9 gene can be used as a marker for chloroplast transformation (Remacle et al, 2009). While the nuclear genome of Chlamydomonas has a high GC content (65%), the chloroplast genome has a low GC content (35%) and transgenes that have the corresponding codon bias are expressed at significantly higher levels (Franklin et al, 2002).…”

Section: Metabolismmentioning

confidence: 99%

The chloroplast transformation toolbox: selectable markers and marker removal

Day

Goldschmidt-Clermont

2011

Plant Biotechnology Journal

175

139

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SummaryPlastid transformation is widely used in basic research and for biotechnological applications. Initially developed in Chlamydomonas and tobacco, it is now feasible in a broad range of species. Selection of transgenic lines where all copies of the polyploid plastid genome are transformed requires efficient markers. A number of traits have been used for selection such as photoautotrophy, resistance to antibiotics and tolerance to herbicides or to other metabolic inhibitors. Restoration of photosynthesis is an effective primary selection method in Chlamydomonas but can only serve as a screening tool in flowering plants. The most successful and widely used markers are derived from bacterial genes that inactivate antibiotics, such as aadA that confers resistance to spectinomycin and streptomycin. For many applications, the presence of a selectable marker that confers antibiotic resistance is not desirable. Efficient marker removal methods are a major attraction of the plastid engineering tool kit. They exploit the homologous recombination and segregation pathways acting on chloroplast genomes and are based on direct repeats, transient co-integration or co-transformation and segregation of trait and marker genes. Foreign site-specific recombinases and their target sites provide an alternative and effective method for removing marker genes from plastids.

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The ARG9 Gene Encodes the Plastid-Resident N -Acetyl Ornithine Aminotransferase in the Green Alga Chlamydomonas reinhardtii

Cited by 32 publications

References 9 publications

Physiological implications of arginine metabolism in plants

Physiological implications of arginine metabolism in plants

Transgene Expression in Microalgae—From Tools to Applications

The chloroplast transformation toolbox: selectable markers and marker removal

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