RESUMO
Metal contamination impacts various aquatic species, and mollusk bivalves are appropriate sentinel organisms in coastal pollution assessment. Metal exposure can disrupt homeostasis, alter gene expression, and harm cellular processes. However, organisms have evolved mechanisms to regulate metal ions and counteract their toxicity. This study examined the effect of acute cadmium (Cd) and zinc (Zn) on metal-related gene expression in gills of Crassostrea gasar following 24 and 48 h of laboratory exposure. We focused on Zn transport, metallothionein (MT), glutathione (GSH) biosynthesis, and calcium (Ca) transporter genes to understand the underlying Cd and Zn-accumulating mechanisms that prevent metal toxicity. Our findings revealed increased Cd and Zn levels in oyster gills, with significantly higher accumulation after 48 h. C. gasar accumulated high Cd concentrations even in scarce conditions and increased Zn levels, suggesting a strategy to cope with toxicity. While no significant gene expression differences were observed after 24 h, the increased metal accumulation after 48 h led to upregulation of CHAC1, GCLC, ZnT2, and MT-like genes in oysters exposed to Cd, and increased ZnT2-like expression following exposure to higher Cd/Zn mixtures. We found evidence of oysters may mobilize metal-related genes to mitigate Cd-induced toxicity by both chelating metals and/or reducing their intracellular concentrations. The observed genes upregulation also indicates their sensitivity to changes in metal bioavailability. Overall, this study offers insights into oyster mechanisms for coping with metal toxicity and suggests ZnT2, MT, CHAC1, and GCLC-like as molecular biomarkers for monitoring aquatic metal pollution using C. gasar as sentinel species.
Assuntos
Crassostrea , Poluentes Químicos da Água , Animais , Cádmio/metabolismo , Zinco/toxicidade , Zinco/metabolismo , Crassostrea/genética , Crassostrea/metabolismo , Poluentes Químicos da Água/metabolismo , Metais/metabolismo , Glutationa/metabolismo , Biomarcadores/metabolismo , Expressão Gênica , Metalotioneína/genética , Metalotioneína/metabolismoRESUMO
Oysters have been extensively employed for monitoring of metal pollution in dynamic aquatic ecosystems. Therefore, the use of specific biomarkers can assist in discriminating the ecotoxicological implications of different elements in such complex environments. In this study, we revisited the sequencing data of gills and digestive glands transcripts in the mangrove oyster Crassostrea gasar and generated a reference transcriptome assembly from multiple assemblers, seven in total. Overall, we were able to identify a total of 11,917 transcripts, with 86.6% of them being functionally annotated and 1.4 times more than the first annotation. We screened the annotated transcripts to identify genes potentially involved in metals' transport, storage, and detoxification. Our findings included genes related to Zn distribution in cells (Zn transporters - ZIP, ZnT), metallothionein (MT-I and MT-IV), GSH biosynthesis, Ca+ transporter (NCX and ATP2B), and Cu distribution in cells (ATP7, ATOX1, CCS, and laccase-like). These results provided a reference transcriptome for additional insights into the transcriptional profile of C. gasar and other bivalves to better understand the molecular pathways underpinning metal tolerance and susceptibility. The study also provided an auxiliary tool for biomonitoring metal contamination in dynamic environments as estuaries.
Assuntos
Crassostrea , Poluentes Químicos da Água , Animais , Biomarcadores/metabolismo , Crassostrea/genética , Crassostrea/metabolismo , Ecossistema , Monitoramento Ambiental , Lacase/metabolismo , Metalotioneína/genética , Metalotioneína/metabolismo , Metais/análise , Transcriptoma , Poluentes Químicos da Água/análiseRESUMO
Two sister orders of the brown macroalgae (class Phaeophyceae), the morphologically complex Laminariales (commonly referred to as kelp) and the morphologically simple Ectocarpales are natural hosts for the dsDNA phaeoviruses (family Phycodnaviridae) that persist as proviruses in the genomes of their hosts. We have previously shown that the major capsid protein (MCP) and DNA polymerase concatenated gene phylogeny splits phaeoviruses into two subgroups, A and B (both infecting Ectocarpales), while MCP-based phylogeny suggests that the kelp phaeoviruses form a distinct third subgroup C. Here we used MCP to better understand the host range of phaeoviruses by screening a further 96 and 909 samples representing 11 and 3 species of kelp and Ectocarpales, respectively. Sporophyte kelp samples were collected from their various natural coastal habitats spanning five continents: Africa, Asia, Australia, Europe, and South America. Our phylogenetic analyses showed that while most of the kelp phaeoviruses, including one from Macrocystispyrifera, belonged to the previously designated subgroup C, new lineages of Phaeovirus in 3 kelp species, Ecklonia maxima, Ecklonia radiata, Undaria pinnatifida, grouped instead with subgroup A. In addition, we observed a prevalence of 26% and 63% in kelp and Ectocarpales, respectively. Although not common, multiple phaeoviral infections per individual were observed, with the Ectocarpales having both intra- and inter-subgroup phaeoviral infections. Only intra-subgroup phaeoviral infections were observed in kelp. Furthermore, prevalence of phaeoviral infections within the Ectocarpales is also linked to their exposure to waves. We conclude that phaeoviral infection is a widely occurring phenomenon in both lineages, and that phaeoviruses have diversified with their hosts at least since the divergence of the Laminariales and Ectocarpales.
Assuntos
Kelp/virologia , Macrocystis/virologia , Phycodnaviridae/classificação , Undaria/virologia , Viroses/virologia , Ásia , Austrália , Proteínas do Capsídeo/genética , DNA Polimerase Dirigida por DNA , Ecossistema , Europa (Continente) , Oceanos e Mares , Phycodnaviridae/isolamento & purificação , Filogenia , Provírus/genética , Provírus/fisiologia , América do Sul , Latência ViralRESUMO
The Brazilian oyster Crassostrea brasiliana was challenged to three common environmental contaminants: phenanthrene, diesel fuel water-accommodated fraction (WAF) and domestic sewage. Total RNA was extracted from the gill and digestive gland, and cDNA libraries were sequenced using the 454 FLX platform. The assembled transcriptome resulted in Ì20,000 contigs, which were annotated to produce the first de novo transcriptome for C. brasiliana. Sequences were screened to identify genes potentially involved in the biotransformation of xenobiotics and associated antioxidant defence mechanisms. These gene families included those of the cytochrome P450 (CYP450), 70kDa heat shock, antioxidants, such as glutathione S-transferase, superoxide dismutase, catalase and also multi-drug resistance proteins. Analysis showed that the massive expansion of the CYP450 and HSP70 family due to gene duplication identified in the Crassostrea gigas genome also occurred in C. brasiliana, suggesting these processes form the base of the Crassostrea lineage. Preliminary expression analyses revealed several candidates biomarker genes that were up-regulated during each of the three treatments, suggesting the potential for environmental monitoring.
Assuntos
Crassostrea/efeitos dos fármacos , Crassostrea/metabolismo , Transcriptoma , Poluentes Químicos da Água/toxicidade , Animais , Biotransformação/genética , Brasil , Crassostrea/genética , Monitoramento Ambiental , Gasolina/toxicidade , Brânquias/metabolismo , Redes e Vias Metabólicas/genética , Fenantrenos/metabolismo , Fenantrenos/toxicidade , Esgotos , Estresse Fisiológico/efeitos dos fármacos , Estresse Fisiológico/genética , Xenobióticos/metabolismo , Xenobióticos/toxicidadeRESUMO
⢠The origin of the Ectocarpus strain used for genome sequencing (the 'genome strain') was Peru, where no Ectocarpus had been reported previously. To study the genetic diversity in the region and to increase the number of individuals from this area available for genetic experiments, 119 new Ectocarpus strains were isolated from eight localities along the 3000 km of coastline from central Peru to central Chile. ⢠Internal transcribed spacer 1 (ITS1) genotyping revealed nine different genotypes, five of which were endemic to the area studied and three of which were previously unknown. ⢠Individuals of the same genotype as the genome strain occurred from Peru to northernmost Chile, representing 61% of the samples in this area, from which five more genotypes were isolated. Further south, down to central Chile, most individuals belonged to Ectocarpus siliculosus, Ectocarpus fasciculatus and Ectocarpus crouaniorum. In sexual crosses, the genome strain and the new isolates of the same genotype were fully compatible. ⢠Sequences from four nuclear and cytoplasmic genetic markers (ITS1, ITS2, Rubisco spacer and Cytochrome-c oxidase subunit 3 (cox3)) separated the genome strain from the known species of Ectocarpus. It may in future be recognized as a separate species.