The convertase furin is involved in the maturation of key growth/aggregation mediators synthesized by the platelet producers, megakaryocytes, but the regulation of furin in these cells remains ...unknown. Computer-assisted search of the furin promoter sequence revealed multiple potential binding motifs for GATA-1, suggesting that furin is expressed and regulated in these cells. Using megakaryoblastic Dami cells, we observed that fur mRNA expression increased gradually on phorbol 12-myristate 13-acetate–induced differentiation, reaching maximum levels (8.3-fold increase) at 10 days. Transient transfections with P1, P1A, or P1B fur-LUC–promoter constructs revealed that in Dami cells, the P1 promoter is the strongest and the most sensitive to forced expression of GATA-1. Coexpression of GATA-1 and its comodulator, Friend of GATA-1 (FOG-1), resulted in a cooperative increase in P1 activity. Deletion analysis indicated that important GATA-1–regulated sequences are located in the most proximal region of the P1 promoter. Further analysis revealed 2 potential GATA-binding motifs at positions −66 and +62. Point mutation of each of the 2 motifs indicated that the intactness of the first GATA site is required for full basal and GATA-1–stimulated promoter activity. Finally, the inhibition of furin activity through gene transfer of the inhibitor α1-AT-PDX led to a block in maturation of the furin substrates transforming growth factor-β1 and platelet-derived growth factor. Taken together, these results indicate that the most proximal GATA element in the P1 promoter is needed forfur gene expression in megakaryoblastic cells. They also suggest that proper regulation of the fur gene in megakaryocytes has an impact on the activation of furin substrates involved in megakaryocyte maturation and platelet functions.
Arctic photoautotrophic communities must survive through polar night darkness until light returns in spring. We tracked changes in the cellular resource allocations and functional capacities of a ...polar sea-ice diatom, Fragilariopsis cylindrus, to understand acclimation processes in both darkness and during the subsequent return to light. We measured parameters at specific time-points over 3 months of darkness, and then over 6 d after a return to light. Measured parameters included cell number and size, cellular carbon and nitrogen quotas, lipid and pigment contents, concentration of key proteins of the photosynthetic system, photosynthetic parameters based on both variable fluorescence and carbon assimilation, and the level of nonphotochemical quenching. A stable functional state was reached within a few days after the transition to dark and was then maintained throughout 3 months of darkness. The dark period resulted in a decrease of lipid droplet cell quota (−6%), chlorophyll a cell quota (−41%) and the maximum carbon fixation rate per cell (−98%). Return to light after 1.5 months of darkness resulted in a strong induction of nonphotochemical quenching of excitation and a fast recovery of the maximum carbon fixation rate within 1 d, followed by a rapid increase in the cell number. Return to light after 3 months of darkness showed an increase of mortality or a profound downregulation induced over longer periods of darkness.
Sequence analysis of the adhesion molecule E-cadherin had revealed a multibasic motif
4PArg-Gln-Lys-Arg
1P, reminiscent of the minimal cleavage signal for furin, the prototype of the proprotein ...convertase family, and/or other members sharing similar sequence specificity. Mutation of this site was sufficient to abolish processing of E-cadherin in fibroblasts reinforcing the possibility that proprotein convertases are involved in the maturation of this adhesion molecule. Here we demonstrate that even though furin can efficiently and specifically cleave proE-cadherin in a baculovirus-based co-expression system, the furin-deficient LoVo cells were found to process endogenous E-cadherin as efficiently as normal cell lines. This suggests, for the first time, that E-cadherin is not only a substrate for furin but for other mammalian convertases sharing similar sequence specificity.
Domestication is an excellent model for studying adaptation processes, involving recent adaptation and diversification, convergence following adaptation to similar conditions, as well as degeneration ...of unused functions. Geotrichum candidum is a fungus used for cheese making and is also found in other environments such as soil and plants. By analyzing whole-genome data from 98 strains, we found that all strains isolated from cheese formed a monophyletic clade. Within the cheese clade, we identified three genetically differentiated populations and we detected footprints of recombination and admixture. The genetic diversity in the cheese clade was similar as that in the wild clade, suggesting the lack of strong bottlenecks. Commercial starter strains were scattered across the cheese clade, thus not constituting a single clonal lineage. The cheese populations were phenotypically differentiated from other populations, with a slower growth on all media, even cheese, a prominent production of typical cheese volatiles and a lower proteolytic activity. One of the cheese clusters encompassed all soft goat cheese strains, suggesting an effect of cheese-making practices on differentiation. Another of the cheese populations seemed to represent a more advanced stage of domestication, with stronger phenotypic differentiation from the wild clade, harboring much lower genetic diversity, and phenotypes more typical of cheese fungi, with denser and fluffier colonies and a greater ability of excluding cheese spoiler fungi. Cheese populations lacked two beta lactamase-like genes present in the wild clade, involved in xenobiotic clearance, and displayed higher contents of transposable elements, likely due to relaxed selection. Our findings suggest the existence of genuine domestication in G. candidum, which led to diversification into different varieties with contrasted phenotypes. Some of the traits acquired by cheese strains indicate convergence with other, distantly related fungi used for cheese maturation.
Domestication is an excellent model for studying adaptation processes, involving recent adaptation and diversification, convergence following adaptation to similar conditions, as well as degeneration ...of unused functions. Geotrichum candidum is a fungus used for cheese making and is also found in other environments such as soil and plants. By analyzing whole-genome data from 98 strains, we found that all strains isolated from cheese formed a monophyletic clade. Within the cheese clade, we identified three genetically differentiated populations and we detected footprints of recombination and admixture. The genetic diversity in the cheese clade was similar as that in the wild clade, suggesting the lack of strong bottlenecks. Commercial starter strains were scattered across the cheese clade, thus not constituting a single clonal lineage. The cheese populations were phenotypically differentiated from other populations, with a slower growth on all media, even cheese, a prominent production of typical cheese volatiles and a lower proteolytic activity. One of the cheese clusters encompassed all soft goat cheese strains, suggesting an effect of cheese-making practices on differentiation. Another of the cheese populations seemed to represent a more advanced stage of domestication, with stronger phenotypic differentiation from the wild clade, harboring much lower genetic diversity, and phenotypes more typical of cheese fungi, with denser and fluffier colonies and a greater ability of excluding cheese spoiler fungi. Cheese populations lacked two beta lactamase-like genes present in the wild clade, involved in xenobiotic clearance, and displayed higher contents of transposable elements, likely due to relaxed selection. Our findings suggest the existence of genuine domestication in G. candidum, which led to diversification into different varieties with contrasted phenotypes. Some of the traits acquired by cheese strains indicate convergence with other, distantly related fungi used for cheese maturation. 1Laboratoire Ecologie Systématique et Evolution,
The Green Edge project was designed to investigate the onset, life and fate of a phytoplankton spring bloom (PSB) in the Arctic Ocean. The lengthening of the ice-free period and the warming of ...seawater, amongst other factors, have induced major changes in arctic ocean biology over the last decades. Because the PSB is at the base of the Arctic Ocean food chain, it is crucial to understand how changes in the arctic environment will affect it. Green Edge was a large multidisciplinary collaborative project bringing researchers and technicians from 28 different institutions in seven countries, together aiming at understanding these changes and their impacts into the future. The fieldwork for the Green Edge project took place over two years (2015 and 2016) and was carried out from both an ice-camp and a research vessel in the Baffin Bay, canadian arctic. This paper describes the sampling strategy and the data set obtained from the research cruise, which took place aboard the Canadian Coast Guard Ship (CCGS) Amundsen in spring 2016. The dataset is available at https://doi.org/10.17882/59892 (Massicotte et al., 2019a).
Durant les années 1970, alors que s’opèrent un développement culturel et une mobilisation politique importante dans le monde autochtone, des centaines de périodiques autochtones voient le jour. ...Kanatha, une de ces revues autogérées, est créée en 1974 comme l’organe du Centre socio‑culturel amérindien Kondiaronk au Village‑Huron (Wendake). En opération jusqu’en 1977, Kanatha, fera paraitre sept numéros. La fondatrice du Centre et de la revue, Éléonore Sioui, femme‑médecine, écrivaine et activiste wendat, devenue docteure en philosophie et spiritualité amérindienne en 1988, vise ainsi à rejoindre les communautés autochtones du pays pour les conscientiser sur les enjeux politiques, sociaux et culturels qui les concernent. Comment s’inscrit l’histoire de Kanatha en lien avec la trajectoire de Sioui comme femme wendat? Kanatha a misé sur la prise de parole politique, l’auto‑représentation et la résurgence des cultures autochtones, et nous offrent une fenêtre sur les visions décoloniales de l’époque.
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