Exploring the Diversity of Red Microalgae for Exopolysaccharide Production

International audienceMicroalgae constitute a remarkable biological diversity but a limited number of them have been the object of study for their ability to produce exoplysaccharides (EPS). Among them, the red marine microalgae Porphyridium or Rhodella produce sulphated EPS, exhibiting some biological activities with potential interest in the pharmaceutical and cosmetic industries. EPS from Porphyridium and Rhodella being relatively similar in their composition, it has long been considered that all the red microalgae produced similar EPS and no attention was paid to other red microalgae. The objective of our work was then to explore the diversity of red microalgae for the production of EPS, focusing in this first step on the screening of the strains for their ability to produce EPS and preliminary structural characterization. The study was conducted with 11 microalgae strains belonging to the proteorhodophytina subphylum. All microalgae were able to produce EPS, released in the culture medium (strains belonging to Porphyridiophyceae and Rhodellophyceae classes) or remaining bound to the cells (strains from Stylonematophyceae class). The analysis of monosaccharides composition was found significantly different, with for instance high levels of glucuronic acids in the EPS from C. japonica and N. cyanea, but also strong differences in the sulphation degrees of polymers (between 1.2 and 28.7% eq. SO4)

Unfolded protein response in cereals, a dynamic signaling pathway involved in response to environmental stresses

International audienceStress of the endoplasmic reticulum (ER) is induced by the accumulation of misfolded proteins in this organelle. It can be triggered by biotic and abiotic stress (particularly heat), but also by chemical treatments (such as DTT and tunicamycin) at a laboratory scale. To respond to this stress, various cellular mechanisms are involved, including the highly conserved protein repair pathway, the UPR (Unfolded Protein Response). This pathway aims to restore protein homeostasis in cells. In cereals, seed storage proteins (SSP) represent one of the characteristics that determine grain quality and are of great interest to agri culture. Unlike dicots, the dynamics of the UPR induction pathway in monocots are poorly documented in the literature. In this review, in addition to the different mechanisms involved in the protein homeostasis maintenance in response to ER stress in cereals, orthologs of UPR induction’s markers have been identified. A focus has been made on the dynamics of the UPR pathway in seedlings and in seeds under chemical UPR inducers (DTT and tunicamycine) and heat stress. The interac tions between the different actors of the UPR pathway are also reviewed and discussed