Résumé
In eukaryotes, the spatial and temporal organization of genome duplication gives rise to distinctive profiles of replication origin usage along the chromosomes. While it has become increasingly clear that these programs are important for cellular physiology, the mechanisms by which they are determined and modulated remain elusive. Replication initiation requires the function of cyclin-dependent kinases (CDKs), which associate with various cyclin partners to drive cell proliferation. Surprisingly, although we possess detailed knowledge of the CDK regulators and targets that are crucial for origin activation, little is known about whether CDKs play a critical role in establishing the genome-wide pattern of origin selection. We have addressed this question in the fission yeast, taking advantage of a simplified cell cycle network in which cell proliferation is driven by a single cyclin-CDK module. This system allows us to precisely control CDK activity in vivo using chemical genetics. First, in contrast to previous reports, our results clearly show that distinct cyclin-CDK pairs are not essential for regulating specific subsets of origins and for establishing a normal replication program. Importantly, we then demonstrate that the timing at which CDK activity reaches the S phase threshold is critical for the organization of replication in distinct efficiency domains, while the level of CDK activity at the onset of S phase is a dose-dependent modulator of overall origin efficiencies. Our study therefore implicates these different aspects of CDK regulation as versatile mechanisms for shaping the architecture of DNA replication across the genome.
Auteurs, date et publication :
Auteurs Anthony Perrot , Christopher Lee Millington , Blanca Gómez-Escoda , Diane Schausi-Tiffoche , Pei-Yun Jenny Wu
Publication : PLOS Genetics
Date : 2025
Volume : 14
Issue : 2
Pages : e1007214
Catégorie(s)
#CNRS #EcoGenO #Université de RennesRésumé
Primary consumers in freshwater ecosystems, such as the zooplankton organism Daphnia magna, are highly affected by cyanobacteria, both as they may use it as a food source but also by cyanobacterial metabolites present in the water. Here, we investigate the impacts of cyanobacterial metabolites focussing on the environmental realistic scenario of the naturally released mixture without crushing cyanobacterial cells or their uptake as food. Therefore, D. magna were exposed to two concentrations of cell free cyanobacterial spent medium from Microcystis aeruginosa PCC 7806 to represent higher and lower ecologically-relevant concentrations of cyanobacterial metabolites. Including microcystin-LR, 11 metabolites have been detected of which 5 were quantified. Hypothesising concentration and time dependent negative impact, survival, gene expression marking digestion and metabolism, oxidative stress response, cell cycle and molting as well as activities of detoxification and antioxidant enzymes were followed for 7 days. D. magna suffered from oxidative stress as both catalase and glutathione S-transferase enzyme activities significantly decreased, suggesting enzyme exhaustibility after 3 and 7 days. Moreover, gene-expressions of the 4 stress markers (glutathione S-transferase, glutathione peroxidase, catalase and thioredoxin) were merely downregulated after 7 days of exposure. Energy allocation (expression of Glyceraldehyde-3-phosphate dehydrogenase) was increased after 3 days but decreased as well after 7 days exposure. Cell cycle was impacted time dependently but differently by the two concentrations, along with an increasing downregulation of myosin heavy chain responsible for cell arrangement and muscular movements. Deregulation of nuclear hormone receptor genes indicate that D. magna hormonal steering including molting seemed impaired despite no detection of microviridin J in the extracts. As a consequence of all those responses and presumably of more than investigated molecular and physiological changes, D. magna survival was impaired over time, in a concentration dependent manner. Our results confirm that besides microcystin-LR, other secondary metabolites contribute to negative impact on D. magna survival and stress response.
Auteurs, date et publication :
Auteurs Gorenka Bojadzija Savic , Hervé Colinet , Myriam Bormans , Christine Edwards , Linda A. Lawton , Enora Briand , Claudia Wiegand
Publication : Toxicon
Date : 2021
Catégorie(s)
#CNRS #EcoGenO #Université de RennesRésumé
The inter- and seasonal patterns of water vapor and canopy carbon fluxes were compared for four forest ecosystems in two contrasting climatic zones in Europe. The eddy covariance and ancillary data were taken from the Carboeurope and FLUXNET databases and a linear modeling statistical analysis was made. The four sites were a high-density poplar (Populus spp.) short rotation coppice plantation (in Lochristi, Belgium) and a mature Scots pine (Pinus sylvestris) forest (in Brasschaat, Belgium) in the Temperate climate versus a fast-growing Eucalypt (Eucalyptus) plantation (in Espirra, Portugal) and a Holm oak (Quercus ilex) forest (in Puechabon, France) in the Mediterranean climate.
Auteurs, date et publication :
Auteurs Gabriel Pita
Publication : Agricultural and Forest Meteorology
Date : 2025
Pages : 14
Catégorie(s)
#CNRS #FORET PuechabonRésumé
The increasing severity and frequency of natural disturbances requires a better understanding of their effects on all compartments of biodiversity. In Northern Fennoscandia, recent large-scale moth outbreaks have led to an abrupt change in plant communities from birch forests dominated by dwarf shrubs to grass-dominated systems. However, the indirect effects on the belowground compartment remained unclear. Here, we combined eDNA surveys of multiple trophic groups with network analyses to demonstrate that moth defoliation has far-reaching consequences on soil food webs. Following this disturbance, diversity and relative abundance of certain trophic groups declined (e.g., ectomycorrhizal fungi), while many others expanded (e.g., bacterivores and omnivores) making soil food webs more diverse and structurally different. Overall, the direct and indirect consequences of moth outbreaks increased belowground diversity at different trophic levels. Our results highlight that a holistic view of ecosystems improves our understanding of cascading effects of major disturbances on soil food webs.
Auteurs, date et publication :
Auteurs Irene Calderón-Sanou , Tamara Münkemüller , Lucie Zinger , Heidy Schimann , Nigel Gilles Yoccoz , Ludovic Gielly , Arnaud Foulquier , Mickael Hedde , Marc Ohlmann , Mélanie Roy , Sara Si-Moussi , Wilfried Thuiller
Publication : Scientific Reports
Date : 2025
Volume : 11
Issue : 1
Pages : 15054
Catégorie(s)
#CNRS #eDNARésumé
Key message The development of a new, low-impact, canopy-access system is described from its original idea until the final realization after about 30 years.
Auteurs, date et publication :
Auteurs Gerhard Gottsberger
Publication : Trees
Date : 2025
Volume : 31
Issue : 3
Pages : 791-812
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Terry W Henkel , Andrew W Wilson , M Catherine Aime , Janina Dierks , Jessie K Uehling , Melanie Roy , Heidy Schimann , Felipe Wartchow , Gregory M Mueller
Publication : Mycologia
Date : 2025
Volume : 106
Issue : 2
Pages : 307-324
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Bart Buyck , Pierre-Arthur Moreau , Régis Courtecuisse , Alejandro Kong , Mélanie Roy , Valérie Hofstetter
Publication : Cryptogamie, Mycologie
Date : 2025
Volume : 37
Issue : 3
Pages : 391-404
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Cessation of traditional management threatens semi-natural grassland diversity through the colonisation or increase of competitive species adapted to nutrient-poor conditions. Regular mowing is one practice that controls their abundance. This study evaluated the ecophysiological mechanisms limiting short- and long-term recovery after mowing for Festuca paniculata, a competitive grass that takes over subalpine grasslands in the Alps following cessation of mowing. We quantified temporal variations in carbon (C) and nitrogen (N) content, starch, fructan and total soluble sugars in leaves, stem bases and roots of F. paniculata during one growth cycle in mown and unmown fields and related them to the dynamics of soil mineral N concentration and soil moisture. Short-term results suggest that the regrowth of F. paniculata following mowing might be N-limited, first because of N dilution by C increments in the plant tissue, and second, due to low soil mineral N and soil moisture at this time of year. However, despite short-term effects of mowing on plant growth, C and N content and concentration at the beginning of the following growing season were not affected. Nevertheless, total biomass accumulation at peak standing biomass was largely reduced compared to unmown fields. Moreover, lower C storage capacity at the end of the growing season impacted C allocation to vegetative reproduction during winter, thereby dramatically limiting the horizontal growth of F. paniculata tussocks in the long term. We conclude that mowing reduces the growth of F. paniculata tussocks through both C and N limitation. Such results will help understanding how plant responses to defoliation regulate competitive interactions within plant communities.
Auteurs, date et publication :
Auteurs F. Baptist , H. Secher-Fromell , F. Viard-Cretat , I. Aranjuelo , J.-C. Clement , A. Creme , M. Desclos , P. Laine , S. Nogues , S. Lavorel
Publication : Plant Biology
Date : 2025
Volume : 15
Issue : 2
Pages : 395-404
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Victoria Meyer , Sassan Saatchi , David B Clark , Michael Keller , Grégoire Vincent , António Ferraz , Fernando Espírito-Santo , Marcus V N Oliveira , Dahlia Kaki , Jérôme Chave
Publication : Biogeosciences
Date : 2025
Volume : 15
Issue : 11
Pages : 3377-3390
Catégorie(s)
#ANR-Citation #CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Andre Obregon , Christine Gehrig-Downie , S Robbert Gradstein , Ruetger Rollenbeck , Joerg Bendix
Publication : Agricultural and Forest Meteorology
Date : 2025
Volume : 151
Issue : 3
Pages : 290-300