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Transcriptomic responses to salinity stress in invasive and native blue mussels (genus Mytilus)

ABSTRACT: The invasive marine mussel Mytilus galloprovincialis has displaced the native congener Mytilus trossulus from central and southern California, but the native species remains dominant at more northerly sites that have high levels of freshwater input. To determine the extent to which interspecific differences in physiological tolerance to low salinity might explain limits to the invasive species’ biogeography, we used an oligonucleotide microarray to compare the transcriptional responses of these two species to an acute decrease in salinity. Among 6,777 genes on the microarray, 117 genes showed significant changes that were similar between species, and 12 genes showed significant species-specific responses to salinity stress. Osmoregulation and cell cycle control were important aspects of the shared transcriptomic response to salinity stress, whereas the genes with species-specific expression patterns were involved in mRNA splicing, polyamine synthesis, exocytosis, translation, cell adhesion, and cell signaling. Forty-five genes that changed expression significantly during salinity stress also changed expression during heat stress, but the direction of change in expression was typically opposite for the two forms of stress. These results (i) provide insights into the role of changes in gene expression in establishing physiological tolerance to acute decreases in salinity, and (ii) indicate that transcriptomic differences between M. galloprovincialis and M. trossulus in response to salinity stress are subtle and involve only a minor fraction of the overall suite of gene regulatory responses.

ORGANISM(S): Mytilus californianus Mytilus galloprovincialis Mytilus trossulus

PROVIDER: GSE25111 | GEO | 2011/01/10

SECONDARY ACCESSION(S): PRJNA134503

REPOSITORIES: GEO

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Project description:The invasive marine mussel Mytilus galloprovincialis has displaced the native congener Mytilus trossulus from central and southern California, but the native species remains dominant at more northerly sites that have high levels of freshwater input. To determine the extent to which interspecific differences in physiological tolerance to low salinity might explain limits to the invasive species’ biogeography, we used an oligonucleotide microarray to compare the transcriptional responses of these two species to an acute decrease in salinity. Among 6,777 genes on the microarray, 117 genes showed significant changes that were similar between species, and 12 genes showed significant species-specific responses to salinity stress. Osmoregulation and cell cycle control were important aspects of the shared transcriptomic response to salinity stress, whereas the genes with species-specific expression patterns were involved in mRNA splicing, polyamine synthesis, exocytosis, translation, cell adhesion, and cell signaling. Forty-five genes that changed expression significantly during salinity stress also changed expression during heat stress, but the direction of change in expression was typically opposite for the two forms of stress. These results (i) provide insights into the role of changes in gene expression in establishing physiological tolerance to acute decreases in salinity, and (ii) indicate that transcriptomic differences between M. galloprovincialis and M. trossulus in response to salinity stress are subtle and involve only a minor fraction of the overall suite of gene regulatory responses. Two species (Mytilus galloprovincialis, Mytilus trossulus), hypo-osmotic shock for four hours (850 mOs/kg), one control group (1000 mOs/kg) sampled at the end of the treatment exposure (850 mOs/kg), one control group (1000 mOs/kg) sampled at the beginning. Biological replicates: 6 in each treatment group, 6 in each control group. Heterologous and homologous hybridization to a microarray constructed from Mytilus californianus and Mytilus galloprovincialis sequences. A reference design that used separate pools of reference RNA for each species was employed. Reference amplified RNA (aRNA) was created for each species by pooling RNA before and after amplification. The reference pool was made up of RNA from six different samples: two base-line control samples from the beginning of the experiment, two treatment samples from the end of the four-hour hypo-osmotic exposure, and two time-control samples from the end of the four-hour exposure time. To accurately compare the transcriptomes of Mytilus galloprovincialis and M. trossulus, we chose to develop a common microarray format that could be used for both species. This microarray design consisted of probe sequences generated from the out-group species, M. californianus. M. trossulus and M. galloprovincialis are approximately 7.5 million years divergent from M. californianus, yet only 3.5 million years divergent from each other (Seed, 1992). Therefore, heterologous hybridization to the microarray allowed us to compare transcriptional responses of M. galloprovincialis and M. trossulus without the inherent sequence biases that would result from a microarray that was designed from sequences of either M. galloprovincialis or M. trossulus. A limited number of sequences (556) from ESTs from M. galloprovincialis that matched M. californianus ESTs were included on the microarray to test for the effects of sequence mismatches. Only probes that performed well for both M. galloprovincialis and M. trossulus were used in our analyses. In order to determine significant changes in expression, we conducted a two-way ANOVA, in which salinity and species were modeled as fixed effects, and focused on genes that were significant for the salinity effect or the species x temperature interaction. We ignored the species term from the ANOVA as this effect could have highlighted genes that differentially bound to probes on the microarray due to differences in sequence homology, thus not reflecting true differences in gene expression. In accordance with statistical convention, all genes with a significant species x temperature interaction were deemed not to have significant temperature effects, even if the temperature term from the ANOVA had a low P-value. All genes with FDR-corrected (Benjamini and Hochberg, 1995) P-values less than 0.05 were considered significant. Analyses were conducted in the R statistical programming environment (R Development Core Team, 2009).

Project description:Pharmaceutical compounds are emerging contaminants in aquatic environment due to their massive use (human and veterinary medicines, agriculture and aquaculture) and a limited removal by waste water treatment plants (WWTPs). In this work, a representative determination of ecotoxicological potential of two different NSAIDs compounds was studied in the sensitive bioindicator marine organism M. Galloprovincialis. Mussels were exposed, under regulated laboratory conditions, to Ketoprofen (KET) and Nimesulide (NIM), dosed alone at the realistic environmental concentration of 0.5Âµg/L for 14 days. Gene expression analyses of Mytilus galloprovincialis exposed to KET and NIM have been performed through a DNA microarray platform. Mussels Mytilus galloprovincialis (5 Â± 1 cm shell length) were obtained from a local farm (Numana, Ancona) and acclimatized for 10 days to laboratory conditions with aerated seawater, at 18 Â± 1 Â°C, 37 â?° salinity, pH 7.5 Â± 0.5 and oxygen saturation >94%. Mussels were distributed into three 17 L aquarium and exposed at 0.5Âµg/L to ketoprofen (KET) and nimesulide (NIM) dosed alone for 14 days. All treatments were compared to control (CTRL) containing 0.00001% of methanol. Water was changed every other day and concentration of molecules were restored. Gene transcription analyses of 12 digestive glands pools (four pools for each treatment composed by 3 digestive glands; CNTR, NIM and KET) were performed using a 8X60K Agilent oligo-DNA microarray platform GPL18667. Microarrays were synthesized in situ using the Agilent non-contact ink-jet technology including default positive and negative controls. Total RNA was isolated using Extract-all (Eurobio) procedure. RNA quality and integrity was controlled on the Agilent bioanalyzer using RNA nanochips and Agilent RNA 6000 nanoreagents (Agilent Technologies, Waldbronn, Germany). RNA concentrations were measured at 260 nm using a ND-1000 spectrophotometer (Nanodrop Technologies) using the conversion factor 1 OD = 40 mg/mL total RNA. Samples were stored at -80Â°C until further use. Gene expression profiling was performed using an Mytilus galloprovincialis oligo-DNA microarray of 59,971 probes based on single-colour detection (Cyanine-3 only). Microarrays were scanned with Agilent scanner G2565BA at a resolution of 2 microns; all slides were scanned twice at two different sensitivity settings (XDRHi 100% and XDRLo 10%); the scanner software created a unique ID for each pair of XDR scans and saved it to both scan image files. FeatureExtraction v10.7.3.1 used XDR ID to link the pairs of scans together automatically when extracting data. The signal left after all the FE processing steps have been completed is ProcessedSignal that contains the Multiplicatively Detrended, Background-Subtracted Signal.

Project description:Five allotetraploid cotton species have adapted, through their transcriptional responses, to unique environments with distinct levels of inherent abiotic stresses. The transcriptional responses of leaf and root tissue in five allotetraploid cotton species (Gossypium hirsutum, G. barbadense, G. tomentosum, G. mustelinum, and G. darwinii) under salt stress have been investigated in this study using cotton long oligonucleotide microarrays. Physiological responses to salinity such as stomatal conductance, ion and osmoprotectant contents were also measured as indicators of imposed stress. Accessions from these five cotton species were hydroponically grown and gradually introduced to a NaCl treatment (15 dS m-1). The microarray results identified 2721 and 2460 differentially expressed genes under salt stress that were significant in leaf and root tissue, respectively. Many of these genes were classified under gene ontology (GO) categories that suggest abiotic stress. These allotetraploid cottons shared transcriptional responses to salinity, but also showed responses that were species-specific. No consistent differences in transcriptional response among the previously estimated phylogenetic branches were found. Stomatal conductance, ion accumulation, and betaine, trigonelline, and trehalose contents also indicated salt stress. This global assessment of transcriptional and physiological responses to salt stress of these cotton species may identify possible gene targets for crop improvement and evolutionary studies of cotton. Keywords: CEGC Cotton oligo salt stress The transcriptional responses of leaf and root tissue in five allotetraploid cotton species (Gossypium hirsutum, G. barbadense, G. tomentosum, G. mustelinum, and G. darwinii) under salt stress have been investigated in this study using cotton long oligonucleotide microarrays. Physiological responses to salinity such as stomatal conductance, ion and osmoprotectant contents were also measured as indicators of imposed stress. Accessions from these five cotton species were hydroponically grown and gradually introduced to a NaCl treatment (15 dS m-1).

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Transcriptomic responses to salinity stress in invasive and native blue mussels (genus Mytilus)

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