Browsing by Author "Destombe, Christophe"

Now showing 1 - 7 of 7
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    After a catastrophe, a little bit of sex is better than nothing: Genetic consequences of a major earthquake on asexual and sexual populations
    (2020) Becheler, Ronan; Guillemin, Marie-Laure; Stoeckel, Solenn; Mauger, S.; Saunier, Alice; Brante Ramírez, Antonio Javier; Destombe, Christophe; Valero, Myriam
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    Differential ecological responses to environmental stress in the life history phases of the isomorphic red alga Gracilaria chilensis (Rhodophyta)
    (2013) Guillemin, Marie-Laure; Sepulveda, Roger D.; Correa, Juan A.; Destombe, Christophe
    In order to better understand the alternation of generations that characterizes haploid-diploid life cycles, we assessed the existence of ecological differences between the two phases (haploid gametophyte and diploid tetrasporophyte) in Gracilaria chilensis, a rhodophyte with a typical Polysiphonia-type life cycle. We investigated the effect of light intensity and salinity on viability and growth of both phases at different ontogenetic stages: juveniles and adults. In our study, the survival of juvenile gametophytes (n) was higher than the survival of juvenile tetrasporophytes (2n) despite culture conditions; however, low salinity had greater effect on carpospores (2n) than on tetraspores (n). On the other hand, a complex interaction between salinity and light intensity within each life history phase generated observed differences between juvenile growth rates. Low light was shown to trigger early onset of alteration of the holdfast growing pattern. In addition, adult tetrasporophytes showed, despite the conditions, a faster vegetative growth than female and male gametophytes. These differences between phases could have led to the complete dominance of tetrasporophyte fragments of fronds observed in G. chilensis farms. We hypothesize that Chilean fishers could have unknowingly selected for tetrasporophyte thalli during domestication of the species, thus enhancing the natural trend of tetrasporophytes dominance already present in estuarine natural populations of free-floating plants.
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    Evidence for parasite-mediated selection during short-lasting toxic algal blooms
    (2016) Blanquart, François; Valero, Myriam; Souza, Catharina Alves de; Dia, Aliou; Lepelletier, Frédéric; Bigeard, Estelle; Jeanthon, Christian; Destombe, Christophe; Guillou, Laure
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    Male gametophyte fragmentation in Laminaria digitata: a life history strategy to enhance reproductive success
    (2011) Destombe, Christophe; Oppligeri, L. Valeria
    An understanding of the life history of Laminaria digitata is crucial to implementing efficient management practices that can ensure the persistence of the kelp forest. L. digitata shows an obligate haplo-diplont heteromorphic life cycle with alternation of a large sporophyte and dioecious microscopic gametophytes. The study of growth and reproduction in culture conditions demonstrated different strategies in male and female gametophytes: Males grew vegetatively and reproduced simultaneously, whereas females stopped growing after reproduction. In addition, we demonstrated that males were able to fragment to give new gametophyte individuals. These results suggest that male and female gametophytes have developed two contrasting reproductive strategies with semelparous females and iteroparous males enhancing the reproductive success of the species.
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    Parallelisable non-invasive biomass, fitness and growth measurement of macroalgae and other protists with nephelometry
    (2020) Calmes, B.; Strittmatter, M.; Jacquemin, B.; Perrineau, M. M.; Rousseau, C.; Badis, Y.; Cock, J. M.; Destombe, Christophe; Valero, Myriam; Gachon, C. M. M.
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    SEX RATIO VARIATION IN THE LESSONIA NIGRESCENS COMPLEX (LAMINARIALES, PHAEOPHYCEAE): EFFECT OF LATITUDE, TEMPERATURE, AND MARGINALITY
    (WILEY, 2011) Oppliger, Luz Valeria; Correa, Juan A.; Faugeron, Sylvain; Beltran, Jessica; Tellier, Florence; Valero, Myriam; Destombe, Christophe
    Little is known about variation of sex ratio, the proportion of males to females, in natural populations of seaweed, though it is a major determinant of the mating system. The observation of sexual chromosomes in kelps suggested that sex is partly genetically determined. However, it is probably not purely genetic since the sex ratio can be modified by environmental factors such as salinity or temperature. In this paper, sex ratio variation was studied in the kelp Lessonia nigrescens Bory complex, recently identified as two cryptic species occurring along the Chilean coast: one located north and the other south of the biogeographic boundary at latitude 29 degrees-30 degrees S. The life cycle of L. nigrescens is characterized by an alternation of microscopic haploid gametophytic individuals and large macroscopic fronds of diploid sporophytes. The sex ratio was recorded in progenies from 241 sporophytic individuals collected from 13 populations distributed along the Chilean coast in order (i) to examine the effect of an environmental gradient coupled with latitude, and (ii) to compare marginal populations to central populations of the two species. In addition, we tested the hypothesis that the sex ratios of the two cryptic species would be affected differently by temperature. First, our results demonstrate that sex ratio seems to be mainly genetically determined and temperature can significantly modify it. Populations of the northern species showed a lower frequency of males at 14 degrees C than at 10 degrees C, whereas populations of the southern species showed the opposite pattern. Second, both species displayed an increased variation in sex ratio at the range limits. This greater variation at the margins could be due either to differential mortality between sexes or to geographic parthenogenesis (asexual reproduction).
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    The Rhodoexplorer Platform for Red Algal Genomics and Whole-Genome Assemblies for Several Gracilaria Species
    (2023) Lipinska, Agnieszka P.; Krueger-Hadfield, Stacy A.; Godfroy, Olivier; Dittami, Simon M.; Ayres-Ostrock, Ligia; Bonthond, Guido; Brillet-Gueguen, Loraine; Coelho, Susana; Corre, Erwan; Cossard, Guillaume; Destombe, Christophe; Epperlein, Paul; Faugeron, Sylvain; Ficko-Blean, Elizabeth; Beltran, Jessica; Lavaut, Emma; Le Bars, Arthur; Marchi, Fabiana; Mauger, Stephane; Michel, Gurvan; Potin, Philippe; Scornet, Delphine; Sotka, Erik E.; Weinberger, Florian; de Oliveira, Mariana Cabral; Guillemin, Marie-Laure; Plastino, Estela M.; Valero, Myriam
    Macroalgal (seaweed) genomic resources are generally lacking as compared with other eukaryotic taxa, and this is particularly true in the red algae (Rhodophyta). Understanding red algal genomes is critical to understanding eukaryotic evolution given that red algal genes are spread across eukaryotic lineages from secondary endosymbiosis and red algae diverged early in the Archaeplastids. The Gracilariales is a highly diverse and widely distributed order including species that can serve as ecosystem engineers in intertidal habitats and several notorious introduced species. The genus Gracilaria is cultivated worldwide, in part for its production of agar and other bioactive compounds with downstream pharmaceutical and industrial applications. This genus is also emerging as a model for algal evolutionary ecology. Here, we report new whole-genome assemblies for two species (Gracilaria chilensis and Gracilaria gracilis), a draft genome assembly of Gracilaria caudata, and genome annotation of the previously published Gracilaria vermiculophylla genome. To facilitate accessibility and comparative analysis, we integrated these data in a newly created web-based portal dedicated to red algal genomics (https://rhodoexplorer.sb-roscoff.fr). These genomes will provide a resource for understanding algal biology and, more broadly, eukaryotic evolution.