Deletion of BSG1 in $Chlamydomonas\ reinhardtii$ leads to abnormal starch granule size and morphology

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Findinier, Justin | Laurent, Sylvain | Duchëne, Thierry | Roussel, Xavier | Lancelon-Pin, Christine | Cuiné, Stéphan | Putaux, Jean-Luc | Li-Beisson, Yonghua | D’hulst, Christophe | Wattebled, Fabrice | Dauvillee, David

Edité par CCSD ; Nature Publishing Group -

International audience. Chlamydomonas reinhardtii represents an ideal model microbial system to decipher starch metabolism.In this green algae, in cells growing in photosynthetic conditions, starch mainly accumulates as asheath surrounding the pyrenoid while in cells subjected to a nutrient starvation, numerous starchgranules are flling up the plastid stroma. The mechanisms underlying and regulating this switchfrom photosynthetic to storage starch metabolisms are not known. In this work, we have isolated aChlamydomonas mutant strain containing a deletion in chromosome 2 which displays abnormal starchgranule distribution. Under nitrogen starvation, this strain contains an additional starch granulespopulation. These granules are twice as big as the wild-type granules and display characteristics ofphotosynthetic starch. Genetic and functional complementation analyses allowed us to identify thegene responsible for this original phenotype which was called BSG1 for “Bimodal Starch Granule”.Possible roles of BSG1 in starch metabolism modifcations during the transition from photosynthetic tostarved growth conditions are discussed.

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