pubmed.ncbi.nlm.nih.gov

Genetic dissection of floridean starch synthesis in the cytosol of the model dinoflagellate Crypthecodinium cohnii - PubMed

  • ️Thu Jan 01 2009

Genetic dissection of floridean starch synthesis in the cytosol of the model dinoflagellate Crypthecodinium cohnii

David Dauvillée et al. Proc Natl Acad Sci U S A. 2009.

Abstract

Starch defines an insoluble semicrystalline form of storage polysaccharides restricted to Archaeplastida (red and green algae, land plants, and glaucophytes) and some secondary endosymbiosis derivatives of the latter. While green algae and land-plants store starch in plastids by using an ADP-glucose-based pathway related to that of cyanobacteria, red algae, glaucophytes, cryptophytes, dinoflagellates, and apicomplexa parasites store a similar type of polysaccharide named floridean starch in their cytosol or periplast. These organisms are suspected to store their floridean starch from UDP-glucose in a fashion similar to heterotrophic eukaryotes. However, experimental proof of this suspicion has never been produced. Dinoflagellates define an important group of both photoautotrophic and heterotrophic protists. We now report the selection and characterization of a low starch mutant of the heterotrophic dinoflagellate Crypthecodinium cohnii. We show that the sta1-1 mutation of C. cohnii leads to a modification of the UDP-glucose-specific soluble starch synthase activity that correlates with a decrease in starch content and an alteration of amylopectin structure. These experimental results validate the UDP-glucose-based pathway proposed for floridean starch synthesis.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.

Starch deposition is impaired in the PP314 mutant strain. (A) Glycogen-containing zymogram gel incubated with UDP-glucose and stained with iodine. The brown bands correspond to the starch synthase activities detected in the wild-type reference strain (Left) and the PP314 (RXA40) mutant strain (Right). (B) Growth curves and polysaccharide accumulation of wild-type and PP314 mutant strains in liquid rich medium. Growth is displayed as closed black and open white circles, respectively, for the wild-type and mutant strains. The amounts of starch synthesized by C. cohnii wild-type (solid diamonds) and PP314 mutant (open diamonds) strain are displayed and expressed as milligrams of starch per milliliter of culture.

Fig. 2.
Fig. 2.

Comparison of the CL distribution profiles for wild-type and mutant amylopectins. After purification on a gel filtration Sepharose CL-2B column, amylopectin was debranched with isoamylase and pullulanase. The resulting glucans were analyzed by CE. The relative proportions for each glucan in the total population are expressed as a percentage of the total number of chains. A and C are, respectively, corresponding to the CL distribution obtained from wild-type amylopectin without and with β-amylase pretreatment. B and D are to the corresponding mutant amylopectin samples. The unbroken lines on B and D correspond to the difference plots obtained by subtracting the mutant CLD to the wild-type CLD.

Fig. 3.
Fig. 3.

Scanning electron microscopy of native purified starch granules from the wild-type (A) and PP314 mutant (B) strains.

Fig. 4.
Fig. 4.

Segregation analysis in the recombinant progeny obtained from the cross between RB1 and ALB1. The colonies of C. cohnii were grown on rich-medium plates and stained with iodine (Upper). The strains displaying a yellow phenotype display a strong (80%) reduction in starch amount. The Lower displays the starch synthases activities detected on glycogen-containing zymograms. The cosegregation between the low-starch yellow phenotype and the modification in starch synthase activities is displayed for 12 recombinant strains harboring both the albinos and the canavanine resistance phenotypes. The two first samples on the Left correspond to the wild-type and the original PP314 mutant strains, respectively.

Similar articles

Cited by

References

    1. Viola R, Nyvall P, Pedersen M. The unique features of starch metabolism in red algae. Proc R Soc Lond B Biol. 2001;268:1417–1422. - PMC - PubMed
    1. Deschamps P, et al. Metabolic symbiosis and the birth of the Plant Kingdom. Mol Biol Evol. 2008;25:536–548. - PubMed
    1. Deschamps P, Moreau H, Worden AZ, Dauvillée D, Ball SG. Early gene duplication within Chloroplastida and its correspondence with relocation of starch metabolism to chloroplasts. Genetics. 2008;178:2373–2387. - PMC - PubMed
    1. Deschamps P, Haferkamp I, d'Hulst C, Neuhaus E, Ball S. The relocation of starch metabolism to chloroplasts: When, why and how. Trends Plants Sci. 2008;13:1802–1816. - PubMed
    1. Deschamps P, et al. The heterotrophic dinoflagellate Crypthecodinium cohnii defines a model genetic system to investigate cytoplasmic starch synthesis. Eukaryot Cell. 2008;7:247–257. - PMC - PubMed

Publication types

MeSH terms

Substances