Browsing by Author "Beltran, Jessica"

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    Contrasting response of Gracilaria chilensis (Gracilariales, Rhodophyta) life cycle stages to epiphyte infection
    (2023) Usandizaga, Sara; Beltran, Jessica; Faugeron, Sylvain; Camus, Carolina
    The red seaweed Gracilaria chilensis, a species extensively cultivated in Chile for agar extraction, was subjected to a bioassay to determine the susceptibility of tetrasporophytes, female and male gametophytes collected from natural and cultivated populations, to the red epiphyte Acrochaetium sp. and the brown epiphyte Ectocarpus sp. The settlement, attachment and germination of epiphytic algal spores on G. chilensis thalli were evaluated, and the photosynthetic responses and the concentration of total phenolic compounds were determined as a possible response of G. chilensis to biotic stress. The results showed that when the thalli were exposed to Acrochaetium infection, female individuals had a significantly lower percentage of germinated spores than other phases of the life cycle. After infection with Ectocarpus spores, males showed the highest % germination of the epiphyte. For both epiphytes, the response of tetrasporophytes from natural and cultivated populations shows a similar trend. The total content of phenolic compounds showed that, in general, the individuals infected with Acrochaetium had a higher defense capacity, whereas the infection with the brown alga did not induce a significant release of phenolic compounds. Despite the heterogeneous results observed for photosynthetic activity, a higher photoinhibition of the maximum fluorescence quantum yield (F-v/F-m) was observed in thalli with the Acrochaetium epiphyte, confirming that G. chilensis was subjected to stress after infection. Taken together, these observations may suggest that the cultivation of females could be of long-term benefit to farms by reducing biomass losses under stressful conditions and epiphyte invasions on farms.
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    Diversity, phenomenology and epidemiology of epiphytism in farmed Gracilaria chilensis (Rhodophyta) in northern Chile
    (2006) Leonardi, Patricia I.; Miravalles, Alicia B.; Faugeron, Sylvain; Flores, Veronica; Beltran, Jessica; Correa, Juan A.
    This study identified the most common epiphytes infecting the algal host Gracilaria chilensis on a farm in northern Chile. Simultaneously, the types of host-epiphyte interfaces were characterized and their relative abundance and temporal variability were monitored. Five types of anatomical relationships were detected. Infection type I included the epiphytes weakly attached to the surface of the host and not associated with damage of host tissues (i.e. Hincksia mitchelliae, H. granulosa and Ectocarpus acutus). Infection type II included those epiphytes strongly attached to the surface of the host but not associated with any host tissue damage (i.e. Acrochaetium sp., Antithamnionella sp. and Colpomenia sinuosa). Infection type III included all the epiphytes that penetrated the outer layer of the host wall without damaging its cortical cells (i.e. Xenococcus sp. and Sahlingia subintegra). Infection type IV included epiphytes penetrating deep into the host cell wall, disorganizing the cortical tissue (i. e. Ulva lactuca and Acrosorium corallinarum). Infection type V included epiphytes that penetrated deeply into the cortex, reached the medullary tissue and caused destruction of the host's cells in the area around the infection (i.e. Ceramium rubrum and Polysiphonia harveyi). Prevalence varied with time and with infection type, with types II and III reaching up to 80% and 90% of the thalli respectively. Severity of epiphyte infection was similar to the distribution of infection prevalence, with crustose epiphytes colonizing up to 80% of the host surface.
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    IDENTIFICATION OF CRYPTIC SPECIES IN THE LESSONIA NIGRESCENS COMPLEX (PHAEOPHYCEAE, LAMINARIALES)
    (WILEY, 2012) Gonzalez, Alejandra; Beltran, Jessica; Hiriart Bertrand, Luciano; Flores, Veronica; de Reviers, Bruno; Correa, Juan A.; Santelices, Bernabe
    The kelp Lessonia nigrescens Bory is the most ecologically and economically important seaweed in rocky intertidal and shallow subtidal habitats along the temperate Pacific South American coasts. Recent molecular studies suggest the existence of two lineages, one (northern lineage) from 17 degrees S to 30 degrees S and a second (central lineage) from 29 degrees S to 41 degrees S. To identify and name these lineages we performed morphological, nomenclatural and field studies. Four external and three internal anatomical traits permitted a morphological separation of the two lineages. The internal structure of both lineages was different from the isolectotype of Lessonia nigrescens. It is therefore concluded that the name Lessonia nigrescens should not be used for the Chilean material. Chordaria spicata Suhr appears as the oldest available name for the central lineage, while Lessonia berteroana Montagne is the oldest name for the northern lineage. In both cases, the type material consisted of small-sized, apical branches of larger plants. The new combination Lessonia spicata (Suhr) Santelices is proposed for the central lineage and we reinstate Lessonia berteroana for the northern lineage. Laminaria scissa Suhr is reduced to synonym of L. spicata. Representative specimens of Lessonia nigrescens were not found during new visits to its type locality in Cape Horn and along Chile. Future studies should verify the status of this species.
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    LUIGI PROVASOLI AWARD RECIPIENTS
    (2009) Thomas, Daniela; Beltran, Jessica; Flores, Veronica; Contreras, Loretto; Bollmann, Edda; Correa, Juan A.
    As part of a long-term study on the biology and ecology of the intertidal kelp Lessonia nigrescens Bory, we report on the occurrence of gall development on this alga, identified the possible causal agent, and assessed the extent of the phenomenon in two wild stands of the host. Our results showed that galls affecting natural populations of L. nigrescens were associated with the infection by a filamentous brown algal endophyte of the genus Laminariocolax. Assignment to Laminariocolax of the endophytes isolated from cultured gall tissue was based on the (i)high internal transcribed spacer 1 (ITS1) sequence similarity and phylogenetic relationship between the Chilean isolates and several species of the genus Laminariocolax endophytic in other kelps, (ii) reproductive and vegetative features of the endophyte in culture, and (iii) anatomical agreement of fully developed galls of Lessonia with those described for other kelp galls caused by endophytic members of Laminariocolax. Unequivocal identification at the species level of the endophytes infecting Lessonia, however, awaits further studies.
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    Morphological convergence in the inter-holdfast coalescence process among kelp and kelp-like seaweeds (Lessonia, Macrocystis, Durvillaea)
    (2015) Gonzalez, Alejandra V.; Beltran, Jessica; Flores, Veronica; Santelices, Bernabe
    In brown macroalgae, intraspecific holdfast coalescence has only been studied in two species of Lessonia (Lessonia spicata and Lessonia berteroana). In both species coalescence followed the same general pattern: once the connection between holdfasts was established, the contact areas showed significant cellular morphological modifications. Typical epidermal cells became polygonal and similar to cortical cells. In addition, coalescence involved the de novo formation of secondary plasmodesmata, establishing a direct cytoplasm connection within neighbouring cells, where dense materials, vacuoles and organelles can be observed. In the present study, we demonstrate intraspecific holdfast coalescence in two additional kelp species, Lessonia trabeculata and Macrocystis pyrifera, as well as in the kelp-like seaweed, Durvillaea antarctica. The process of holdfast fusions in these species is similar to that described previously and suggests that this is a generalized phenomenon among kelp and kelp-like brown algae. In addition, the formation of cytoplasmic connections between genetically different brown algal individuals is shown for the first time.
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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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    Spore release in Acrochaetium sp (Rhodophyta) is bacterially controlled
    (2007) Weinberger, Florian; Beltran, Jessica; Correa, Juan A.; Lion, Ulrich; Pohnert, Georg; Kumar, Naresh; Steinberg, Peter; Kloareg, Bernard; Potin, Philippe
    The facultative red algal epiphyte Acrochaetium sp. liberated spores preferentially and recruited more successfully in laboratory cultures when its host Gracilaria chilensis C. J. Bird, McLachlan et E. C. Oliveira was present. The same effect was also induced by cell-free medium from G. chilensis, suggesting it contained a molecular signal. Antibiotics prevented spore release in Acrochaetium sp., even when G. chilensis was present, suggesting a prokaryotic origin of the signal. Simultaneous application of N-butyl-homoserine-lactone (BHL) restored the spore-release capacity, which demonstrated that spore release was not directly inhibited by the antibiotics and indicated that bacterially generated N-acyl-homoserine-lactones (AHLs) regulate spore release. An involvement of AHL was further indicated by the fact that two different halofuranone inhibitors of AHL receptors also inhibited spore release when they were applied at relatively low concentrations. Of seven different AHLs tested, only BHL induced the effect. However, BHL was only active at relatively high concentrations (100 mu M), and it was not detected in spore-release-inducing medium of G. chilensis. Another water-soluble AHL or an AHL structure analog is therefore probably the active compound in G. chilensis cultures. The data presented demonstrate that life cycle completion in Acrochaetium sp. strongly depends on bacteria, which are not always present in sufficient numbers on the alga itself. Exogenous bacteria that are associated with G. chilensis or with other potential substrates may therefore trigger timely spore liberation in Acrochaetium sp., provided that the necessary concentration of AHL is reached. This first finding of AHL perception in a red alga confirms that AHL signalling is more widespread among eukaryotes than was thought until recently. However, spore release of a second red alga, Sahlingia subintegra (Rosenv.) Kornmann, was unaffected by AHL, and the reaction observed is therefore not universal.
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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.