Browsing by Issue Date, starting with "2018-01-16"
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- Response to simulated El Niño stress by Macrocystis pyriferaPublication . Barreto, Luís António de Matos; Serrão, Ester; Pearson, Gareth; Ladah, LydiaCompelling evidence on environmental and species distribution changes due to global climate change have greatly increased over the last decades and extreme events like marine heatwaves (MHWs) (concurrent high temperature and low nutrient) are increasing in frequency, duration and intensity. The giant kelp, Macrocystis pyrifera (L.) C.A. Agardh forms dense marine forests serving as a foundation species in ecosystems that are of great ecological and economic importance. Thus, the objective of this study was to test for evidence of local adaptation to conditions representative of MHWs stress in the field on a regional level, encompassing areas with different oceanographic regimes and genetic groups. Adult blades from two depths and four regions of the Northeast Pacific were exposed to simulated nutrient and thermal stress conditions. The results clearly showed that M. pyrifera populations at the southernmost limit displayed greater thermal tolerance in their photosynthetic physiology. Compared to the other regions, surface blades from the South suffered reduced impact on the photosynthetic apparatus, with Fv/Fm values at 24ºC 15.5% higher than the regional mean. Thermally-sensitive parameters governed mainly by enzymatic processes (rETRmax and Ek) were unaffected over the 15 - 24ºC range in the southernmost region, suggesting adaptation to local environmental conditions. Amongst the bottom blades collected at depth, photosynthetic responses to stress were rather similar among different regions. The F1 juvenile generation grown in vitro from parental source material did not exhibit a significant reductions in Fv/Fm under the moderate stress temperature used (21ºC), but rETRmax and Ek remained significantly higher in the Southern regions. Consistently poor photosynthetic responses to thermal stress were observed in the North-Center region (Santa Barbara) in all experiments, suggesting genetically-based fitness reduction. Our results also highlighted the need for further research on the synergistic effects of low nutrients availability and high thermal stress considering different life stages of M. pyrifera.
- The role of miRNA-mediated cis-regulation in breast cancer susceptibilityPublication . Fernandes, Ana Catarina Jacinta; Maia, Ana Teresa; Xavier, JoanaCis-regulation of gene expression is believed to be central in breast cancer (BC) predisposition. Here we aimed to unravel the contribution of allele-specific miRNA regulation to BC risk. We screened the effect of 223 published BC genome wide association studies (GWAS) -significant single nucleotide polymorphisms (SNPs) (and their 2668 unique proxies in high linkage disequilibrium) on differential miRNA-regulation. We filtered these SNPs based on location in miRNA genes and/or messenger RNA (mRNA) of protein-coding genes. Selected SNPs were then evaluated for putative differential miRNA-binding using TargetScan and miRanda, two distinct miRNA-target prediction algorithms, modified to analyse sequences carrying SNP alleles. Results were filtered for miRNAs with evidence of expression in breast tissue, and for genes displaying differential allelic expression (DAE), a hallmark of cis-regulation. To validate our findings, we prioritized the candidate SNPs for functional characterization, by combining TargetScan’ and miRanda’ predictions. Interestingly, none of the SNPs mapped to miRNA genes, thus suggesting that miRNA biogenesis and target-binding alteration, via seed sequence modification, are mechanisms unlikely to be involved in BC risk. Of the SNPs located in mRNA sequences we found 93 out of 3891 that were predicted to alter the miRNA-mRNA binding in 27 BC-associated risk loci. From our predictions, we found rs4245739 in MDM4 and rs11540855 in ABHD8, already functionally validated by others to cause allele-specific miRNA-binding. We carried in vitro functional characterization of rs6884232 in ATG10, one of the best candidates identified by both TargetScan and miRanda algorithms. The predicted specific binding of hsa-miR-21-3p to the G allele of this SNP was evaluated using a dual-luciferase system, with constructs carrying either the A or the G allele, and in combination with miRNA mimics and inhibitors in a breast adenocarcinoma cell line. However, no allele-specific specific differences in luciferase activity were observed. To our knowledge, this is the first study looking into the global role of miRNA regulation in BC risk, further improved by the integration of DAE data from normal breast samples.