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

Justin Findinier (1) , Sylvain Laurent (1) , Thierry Duchëne (1) , Xavier Roussel (1) , Christine Lancelon-Pin (2) , Stéphan Cuiné (3, 4) , Jean-Luc Putaux (5) , Yonghua Li-Beisson (3, 4) , Christophe D’hulst (1) , Fabrice Wattebled (1) , David Dauvillee (1)

1 UGSF - Unité de Glycobiologie Structurale et Fonctionnelle - UMR 8576
2 CERMAV - Centre de Recherches sur les Macromolécules Végétales
3 BIAM - Institut de Biosciences et Biotechnologies d'Aix-Marseille (ex-IBEB)
4 EBMP - Environnement, Bioénergie, Microalgues et Plantes
5 CNRS - Centre National de la Recherche Scientifique

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 a sheath surrounding the pyrenoid while in cells subjected to a nutrient starvation, numerous starch granules are flling up the plastid stroma. The mechanisms underlying and regulating this switch from photosynthetic to storage starch metabolisms are not known. In this work, we have isolated a Chlamydomonas mutant strain containing a deletion in chromosome 2 which displays abnormal starch granule distribution. Under nitrogen starvation, this strain contains an additional starch granules population. These granules are twice as big as the wild-type granules and display characteristics of photosynthetic starch. Genetic and functional complementation analyses allowed us to identify the gene 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 to starved growth conditions are discussed.

Domaines: Sciences du Vivant [q-bio]

Justin Findinier, Sylvain Laurent, Thierry Duchëne, Xavier Roussel, Christine Lancelon-Pin, et al.. Deletion of BSG1 in $Chlamydomonas\ reinhardtii$ leads to abnormal starch granule size and morphology. Scientific Reports, 2019, 9, pp.1990. ⟨10.1038/s41598-019-39506-6⟩. ⟨cea-02122889⟩