Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

The Antarctic Krill Euphausia superba Shows Diurnal Cycles of Transcription under Natural Conditions.

ABSTRACT: BACKGROUND: Polar environments are characterized by extreme seasonal changes in day length, light intensity and spectrum, the extent of sea ice during the winter, and food availability. A key species of the Southern Ocean ecosystem, the Antarctic krill (Euphausia superba) has evolved rhythmic physiological and behavioral mechanisms to adapt to daily and seasonal changes. The molecular organization of the clockwork underlying these biological rhythms is, nevertheless, still only partially understood. METHODOLOGY/PRINCIPAL FINDINGS:The genome sequence of the Antarctic krill is not yet available. A normalized cDNA library was produced and pyrosequenced in the attempt to identify large numbers of transcripts. All available E. superba sequences were then assembled to create the most complete existing oligonucleotide microarray platform with a total of 32,217 probes. Gene expression signatures of specimens collected in the Ross Sea at five different time points over a 24-hour cycle were defined, and 1,308 genes differentially expressed were identified. Of the corresponding transcripts, 609 showed a significant sinusoidal expression pattern; about 40% of these exibithed a 24-hour periodicity while the other 60% was characterized by a shorter (about 12-hour) rhythm. We assigned the differentially expressed genes to functional categories and noticed that those concerning translation, proteolysis, energy and metabolic process, redox regulation, visual transduction and stress response, which are most likely related to daily environmental changes, were significantly enriched. Two transcripts of peroxiredoxin, thought to represent the ancestral timekeeping system that evolved about 2.5 billion years ago, were also identified as were two isoforms of the EsRh1 opsin and two novel arrestin1 sequences involved in the visual transduction cascade. CONCLUSIONS: Our work represents the first characterization of the krill diurnal transcriptome under natural conditions and provides a first insight into the genetic regulation of physiological changes, which occur around the clock during an Antarctic summer day Gene expression profiling was carried out in krill fished at different times throughout the 24 hours cycle (local times: 01:00, 06:00, 10:00, 15:00, and 18:00) with the M-bM-^@M-^XM-bM-^@M-^XKrill 1.1M-bM-^@M-^YM-bM-^@M-^Y custom platform (Agilent). We analyzed four different biological replicates for each time point for a total of 20 microarray experiments.

ORGANISM(S): Euphausia superba

SUBMITTER: Cristiano De Pitta

PROVIDER: E-GEOD-42292 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

The Antarctic krill Euphausia superba shows diurnal cycles of transcription under natural conditions.

De Pittà Cristiano C Biscontin Alberto A Albiero Alessandro A Sales Gabriele G Millino Caterina C Mazzotta Gabriella M GM Bertolucci Cristiano C Costa Rodolfo R

PloS one 20130717 7

<h4>Background</h4>Polar environments are characterized by extreme seasonal changes in day length, light intensity and spectrum, the extent of sea ice during the winter, and food availability. A key species of the Southern Ocean ecosystem, the Antarctic krill (Euphausia superba) has evolved rhythmic physiological and behavioral mechanisms to adapt to daily and seasonal changes. The molecular organization of the clockwork underlying these biological rhythms is, nevertheless, still only partially ...[more]

PMID: 23874706

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Project description:We combined heritability analysis of larval development rate with a global expression analysis of this phenotype to investigate genotype by environment interactions across three ecologically relevant temperatures in the Glanville fritillary butterfly (Melitaea cinxia). We focused upon the development of final instar caterpillars which is greatly affected by temperature, and during this stage the caterpillars build up most of the resources for adult life. Second generation, lab reared larvae, initially collected from the M-CM-^Eland metapopulation, were reared in standard lab condition until 6th larval instar. At the beginning of the final (7th) instar stage the larvae were separated into of three temperature conditions: Cold treatment (temperature profile: 8M-BM-0C 18:00-9:59, 14M-BM-0C 10:00-11:59, 20M-BM-0C 12:00-15:59 and 14M-BM-0C 16:00-17:59) Standard treatment (temperature profile: 15M-BM-0C 17:00-6:59, 18M-BM-0C 7:00-8:59, 22M-BM-0C 9:00-10:59 and 26M-BM-0C 11:00-16:59) Hot treatment (temperature profile: 8M-BM-0C 20:00-7:59, 15M-BM-0C 8:00-9:59, 35M-BM-0C 10:00-17:59 and 15M-BM-0C 18:00-19:59) The temperature profiles mimic the diurnal thermal variation of the natural habitat (M-CM-^Eland islands) of samples. Cold treatment mimics a cool and cloudy summer, Standard represents an average temperature profile in the M-CM-^Eland islands and Hot treatment mimics an exceptionally hot and sunny summer, with cold night-time temperatures. The experiment contained several larval families (full-sib) of which three were selected for gene expression analysis. Samples were snap-frozen in liquid nitrogen during mid-development (after 6, 5 and 4 days, for Cold, Standard and Hot respectively). Additional larvae from the same treatments were assayed for survival and growth. Gene expression was analyzed using a mixed model approach to identify genes with potential heritable expression variation (variation among families), genes with plastic expression responses (treatment induced changes) and genes with treatment dependent expression that varies among families (family by treatment interactions). Full-sib larvae from three families (N170, N74 and O171) were exposed to three temperature treatments (Cold, Standard and Hot) during final (7th) instar stage. A total of 35 samples were used to analyze family, treatment and family by treatment interactions in gene expression, using a mixed model approach. This included 3 biological replicates in Cold and Hot treatments from each family and 5-6 biological replicates in Standard (5 in O171) per family. Techinal replicates from each family and additional techical replicates in family O171 (including dye swap replicates) were used to assess robustness of the findings.

Project description:BACKGROUND: Polar environments are characterized by extreme seasonal changes in day length, light intensity and spectrum, the extent of sea ice during the winter, and food availability. A key species of the Southern Ocean ecosystem, the Antarctic krill (Euphausia superba) has evolved rhythmic physiological and behavioral mechanisms to adapt to daily and seasonal changes. The molecular organization of the clockwork underlying these biological rhythms is, nevertheless, still only partially understood. METHODOLOGY/PRINCIPAL FINDINGS:The genome sequence of the Antarctic krill is not yet available. A normalized cDNA library was produced and pyrosequenced in the attempt to identify large numbers of transcripts. All available E. superba sequences were then assembled to create the most complete existing oligonucleotide microarray platform with a total of 32,217 probes. Gene expression signatures of specimens collected in the Ross Sea at five different time points over a 24-hour cycle were defined, and 1,308 genes differentially expressed were identified. Of the corresponding transcripts, 609 showed a significant sinusoidal expression pattern; about 40% of these exibithed a 24-hour periodicity while the other 60% was characterized by a shorter (about 12-hour) rhythm. We assigned the differentially expressed genes to functional categories and noticed that those concerning translation, proteolysis, energy and metabolic process, redox regulation, visual transduction and stress response, which are most likely related to daily environmental changes, were significantly enriched. Two transcripts of peroxiredoxin, thought to represent the ancestral timekeeping system that evolved about 2.5 billion years ago, were also identified as were two isoforms of the EsRh1 opsin and two novel arrestin1 sequences involved in the visual transduction cascade. CONCLUSIONS: Our work represents the first characterization of the krill diurnal transcriptome under natural conditions and provides a first insight into the genetic regulation of physiological changes, which occur around the clock during an Antarctic summer day

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Dataset Information

The Antarctic Krill Euphausia superba Shows Diurnal Cycles of Transcription under Natural Conditions.

Publications

The Antarctic krill Euphausia superba shows diurnal cycles of transcription under natural conditions.

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