Evidence for a role of Arabidopsis CDT1 proteins in gametophyte development and maintenance of genome integrity

Meristems retain the ability to divide throughout the life cycle of plants, which can last for over 1000 years in some species. Furthermore, the germline is not laid down early during embryogenesis but originates from the meristematic cells relatively late during development. Thus, accurate cell cycle regulation is of utmost importance to avoid the accumulation of mutations during vegetative growth and reproduction. The Arabidopsis thaliana genome encodes two homologs of the replication licensing factor CDC10 Target1 (CDT1), and overexpression of CDT1a stimulates DNA replication. Here, we have investigated the respective functions of Arabidopsis CDT1a and CDT1b. We show that CDT1 proteins have partially redundant functions during gametophyte development and are required for the maintenance of genome integrity. Furthermore, CDT1-RNAi plants show endogenous DNA stress, are more tolerant than the wild type to DNA-damaging agents, and show constitutive induction of genes involved in DNA repair. This DNA stress response may be a direct consequence of reduced CDT1 accumulation on DNA repair or may relate to the ability of CDT1 proteins to form complexes with DNA polymerase e, which functions in DNA replication and in DNA stress checkpoint activation. Taken together, our results provide evidence for a crucial role of Arabidopsis CDT1 proteins in genome stability

Rôle de l'activation de la Nadph-Oxydase sur l'externalisation de la phosphatidylserine dans les granulocytes

LE KREMLIN-B.- PARIS 11-BU Méd (940432101) / SudocSudocFranceF

Chapitre 20 - Les applications en biologie végétale : contraintes, succès, espoirs

International audienc

Gut microbial ecology of Xenopus tadpoles across life stages

representedand under-studied in the literature. Among anuran amphibians, Africanclawed frogs of the Xenopus genus stand as well-characterized models with an in-depthknowledge of their developmental biological processes including their metamorphosis.In this study, we analyzed the succession of microbial communities and their activitiesacross diverse body habitats of Xenopus tropicalis using dierent approaches includingow cytometry and 16s rDNA gene metabarcoding. We also evaluated the metaboliccapacity of the premetamorphic tadpoles gut microbiome using metagenomic and metatranscriptomicsequencing. Results:We analyzed the bacterial components of the Xenopusgut microbiota, the adult gut biogeography, the succession of communities duringontogeny, the impact of the alimentation in shaping the tadpoles gut bacterial communitiesand the transmission of skin and fecal bacteria to the eggs. We also identiedthe most active gut bacteria and their metabolic contribution to tadpole physiology includingcarbohydrate breakdown, nitrogen recycling, essential amino-acids and vitaminbiosynthesis. Conclusions: We present a comprehensive new microbiome dataset of alaboratory amphibian model. Our data provide evidences that studies on the Xenopustadpole model can shed light on the interactions between a vertebrate host and its microbiome.We interpret our ndings in light of bile acids being key molecular componentsregulating the gut microbiome composition during amphibian development and metamorphosis.Further studies into the metabolic interactions between amphibian tadpolesand their microbiota during early development and metamorphosis should provide usefulinformation on the evolution of host-microbiota interactions in vertebrates

High-throughput measurement of recombination rates and genetic interference in Saccharomyces cerevisiae

International audienceAllelic recombination owing to meiotic crossovers is a major driver of genome evolution, as well as a key player for the selection of high-performing genotypes in economically important species. Therefore, we developed a high-throughput and low-cost method to measure recombination rates and crossover patterning (including interference) in large populations of the budding yeast Saccharomyces cerevisiae. Recombination and interference were analysed by flow cytometry, which allows time-consuming steps such as tetrad microdissection or spore growth to be avoided. Moreover, our method can also be used to compare recombination in wild-type vs. mutant individuals or in different environmental conditions, even if the changes in recombination rates are small. Furthermore, meiotic mutants often present recombination and/or pairing defects affecting spore viability but our method does not involve growth steps and thus avoids filtering out non-viable spores

Role of Cis, Trans, and Inbreeding Effects on Meiotic Recombination in Saccharomyces cerevisiae

WOS:000452315900007International audienceMeiotic recombination is a major driver of genome evolution by creating new genetic combinations. To probe the factors driving variability of meiotic recombination, we used a high-throughput method to measure recombination rates in hybrids between SK1 and a total of 26 Saccharomyces cerevisiae strains from different geographic origins and habitats. Fourteen intervals were monitored for each strain, covering chromosomes VI and XI entirely, and part of chromosome I. We found an average number of crossovers per chromosome ranging between 1.0 and 9.5 across strains ("domesticated" or not), which is higher than the average between 0.5 and 1.5 found in most organisms. In the different intervals analyzed, recombination showed up to ninefold variation across strains but global recombination landscapes along chromosomes varied less. We also built an incomplete diallel experiment to measure recombination rates in one region of chromosome XI in 10 different crosses involving five parental strains. Our overall results indicate that recombination rate is increasingly positively correlated with sequence similarity between homologs (i) in DNA double-strand-break-rich regions within intervals, (ii) in entire intervals, and (iii) at the whole genome scale. Therefore, these correlations cannot be explained by cis effects only. We also estimated that cis and trans effects explained 38 and 17%, respectively, of the variance of recombination rate. In addition, by using a quantitative genetics analysis, we identified an inbreeding effect that reduces recombination rate in homozygous genotypes, while other interaction effects (specific combining ability) or additive effects (general combining ability) are found to be weak. Finally, we measured significant crossover interference in some strains, and interference intensity was positively correlated with crossover number