RESUMO
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RESUMO
Macrocystis pyrifera and Lessonia spicata are economically and ecologically relevant brown seaweeds that recently have been classified as members of two separated families within Laminariales (kelps). Here we describe for the first time the Macrocystis pyrifera x Lessonia spicata hybridization in the wild (Chiloe Island, Southeastern Pacific), where populations of the two parents exist sympatrically. Externally, this hybrid exhibited typical features of its parents M. pyrifera (cylindrical and flexible distal stipes, serrate frond margins and presence of sporophylls) and L. spicata (rigid and flat main stipe and first bifurcation), as well as intermediate features between them (thick unfused haptera in the holdfast). Histological sections revealed the prevalence of mucilage ducts within stipes and fronds (absent in Lessonia) and fully developed unilocular sporangia in the sporophylls. Molecular analyses confirmed the presence of the two parental genotypes for ITS1 nrDNA and the M. pyrifera genotype for two predominantly maternally inherited cytoplasmic markers (COI and rbcLS spacer) in the tissue of the hybrid. A metabolome-wide approach revealed that this hybrid is more chemically reminiscent to M. pyrifera. Nevertheless, several hits were identified as Lessonia exclusive or more remarkably, not present in any of the parent. Meiospores developed into apparently fertile gametophytes, which gave rise to F1 sporophytes that reached several millimeters before suddenly dying. In-vitro reciprocal crossing of Mar Brava gametophytes from both species revealed that although it is rare, interfamilial hybridization between the two species is possible but mostly overcome by pseudogamy of female gametophytes.
Assuntos
Técnicas de Genotipagem/métodos , Laminaria/fisiologia , Macrocystis/fisiologia , Metabolômica/métodos , DNA de Algas/genética , Genótipo , Hibridização Genética , Melhoramento Vegetal , Esporângios/fisiologia , SimpatriaRESUMO
Recent findings on holdfast development in the giant kelp highlighted its key importance for Macrocystis vegetative propagation. We report here for the first time the development of adventitious holdfasts from Macrocystis stipes. Swellings emerge spontaneously from different areas of the stipes, especially in senescent or creeping individuals. After being manually fastened to solid substrata, these swellings elongated into haptera, which became strongly attached after 1 month. Within 4 months, new thalli increased in size and vitality, and developed reproductive fronds. Our results suggest the usage of these structures for auxiliary attachment techniques. These could act as a backup, when primary holdfasts are weak, and thus improve the survival rate of the giant kelp in natural beds.
Assuntos
Kelp/fisiologia , Macrocystis/fisiologia , Chile , Kelp/crescimento & desenvolvimento , Macrocystis/crescimento & desenvolvimento , ReproduçãoRESUMO
The present paper deals with the ultrastructure of zoospores produced by the plasmodiophorid Maullinia ectocarpii, living in the marine algal host Ectocarpus siliculosus. The zoospores described here are very similar to secondary zoospores of Polymyxa graminis and Phagomyxa sp. (the latter an algal endoparasite, also). Our results indicate that M. ectocarpii produces two types of plasmodia, and suggest that is a species with a complete life cycle, as it is known for all the Plasmodiophormycota that have been studied. Sporogenic and sporangial plasmodia produce, respectively, primary zoospores with parallel flagella within thick walled resting sporangia, and secondary zoospores with opposite flagella within thin walled sporangia.
Assuntos
Plasmodioforídeos/ultraestrutura , Flagelos/ultraestrutura , Microscopia Eletrônica de Transmissão , Phaeophyceae/parasitologia , Plasmodioforídeos/parasitologia , Esporos de Protozoários/ultraestruturaRESUMO
The present paper deals with the ultrastructure of zoospores produced by the plasmodiophorid Maullinia ectocarpii, living in the marine algal host Ectocarpus siliculosus. The zoospores described here are very similar to secondary zoospores of Polymyxa graminis and Phagomyxa sp. (the latter an algal endoparasite, also). Our results indicate that M. ectocarpii produces two types of plasmodia, and suggest that is a species with a complete life cycle, as it is known for all the Plasmodiophormycota that have been studied. Sporogenic and sporangial plasmodia produce, respectively, primary zoospores with parallel flagella within thick walled resting sporangia, and secondary zoospores with opposite flagella within thin walled sporangia.(AU)
Assuntos
Flagelos/ultraestrutura , Phaeophyceae/parasitologia , Esporos de Protozoários/ultraestrutura , Microscopia Eletrônica de TransmissãoRESUMO
The present paper deals with the ultrastructure of zoospores produced by the plasmodiophorid Maullinia ectocarpii, living in the marine algal host Ectocarpus siliculosus. The zoospores described here are very similar to secondary zoospores of Polymyxa graminis and Phagomyxa sp. (the latter an algal endoparasite, also). Our results indicate that M. ectocarpii produces two types of plasmodia, and suggest that is a species with a complete life cycle, as it is known for all the Plasmodiophormycota that have been studied. Sporogenic and sporangial plasmodia produce, respectively, primary zoospores with parallel flagella within thick walled resting sporangia, and secondary zoospores with opposite flagella within thin walled sporangia.
Assuntos
Esporos de Protozoários/ultraestrutura , Flagelos/ultraestrutura , Phaeophyceae/parasitologia , Microscopia Eletrônica de TransmissãoRESUMO
In the marine environment, a growing body of evidence points to parasites as key players in the control of population dynamics and overall ecosystem structure. However, their prevalence and impact on marine macroalgal communities remain virtually unknown. Indeed, infectious diseases of seaweeds are largely underdocumented, partly because of the expertise required to diagnose them with a microscope. Over the last few years, however, real-time quantitative PCR (qPCR) has emerged as a rapid and reliable alternative to visual symptom scoring for monitoring pathogens. Thus, we present here a qPCR assay suitable for the detection and quantification of the intracellular oomycete pathogen Eurychasma dicksonii in its ectocarpalean and laminarialean brown algal hosts. qPCR and microscopic observations made of laboratory-controlled cultures revealed that clonal brown algal strains exhibit different levels of resistance against Eurychasma, ranging from high susceptibility to complete absence of symptoms. This observation strongly argues for the existence of a genetic determinism for disease resistance in brown algae, which would have broad implications for the dynamics and genetic structure of natural populations. We also used qPCR for the rapid detection of Eurychasma in filamentous brown algae collected in Northern Europe and South America and found that the assay is specific, robust, and widely applicable to field samples. Hence, this study opens the perspective of combining large-scale disease monitoring in the field with laboratory-controlled experiments on the genome model seaweed Ectocarpus siliculosus to improve our understanding of brown algal diseases.