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

David Dauvillée (1) , Philippe Deschamps (1) , Jean-Philippe Ral (2) , Charlotte Plancke (1) , Jean-Luc Putaux (3) , Jimi Devassine (1) , Amandine Durand-Terrasson (3) , Aline Devin (1) , Steven Ball (1)

1 UGSF - Unité de Glycobiologie Structurale et Fonctionnelle - UMR 8576
2 CSIRO Plant Industry
3 CERMAV - Centre de Recherches sur les Macromolécules Végétales

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.

Domaines: Biochimie [q-bio.BM]

David Dauvillée, Philippe Deschamps, Jean-Philippe Ral, Charlotte Plancke, Jean-Luc Putaux, et al.. Genetic dissection of floridean starch synthesis in the cytosol of the model dinoflagellate Crypthecodinium cohnii.. Proceedings of the National Academy of Sciences of the United States of America, 2009, 106 (50), pp.21126-21130. ⟨10.1073/pnas.0907424106⟩. ⟨hal-00436589⟩