Differentiation at the MHCIIα and Cath2 Loci in Sympatric Salvelinus alpinus Resource Morphs in Lake Thingvallavatn

Publisher's versionNorthern freshwater fish may be suitable for the genetic dissection of ecological traits because they invaded new habitats after the last ice age (∼10.000 years ago). Arctic charr (Salvelinus alpinus) colonizing streams and lakes in Iceland gave rise to multiple populations of small benthic morphotypes, often in sympatry with a pelagic morphotype. Earlier studies have revealed significant, but subtle, genetic differentiation between the three most common morphs in Lake Thingvallavatn. We conducted a population genetic screen on four immunological candidate genes Cathelicidin 2 (Cath2), Hepcidin (Hamp), Liver expressed antimicrobial peptide 2a (Leap-2a), and Major Histocompatibility Complex IIα (MHCIIα) and a mitochondrial marker (D-loop) among the three most common Lake Thingvallavatn charr morphs. Significant differences in allele frequencies were found between morphs at the Cath2 and MHCIIα loci. No such signal was detected in the D-loop nor in the other two immunological genes. In Cath2 the small benthic morph deviated from the other two (FST = 0.13), one of the substitutions detected constituting an amino acid replacement polymorphism in the antimicrobial peptide. A more striking difference was found in the MHCIIα. Two haplotypes were very common in the lake, and their frequency differed greatly between the morphotypes (from 22% to 93.5%, FST = 0.67). We then expanded our study by surveying the variation in Cath2 and MHCIIα in 9 Arctic charr populations from around Iceland. The populations varied greatly in terms of allele frequencies at Cath2, but the variation did not correlate with morphotype. At the MHCIIα locus, the variation was nearly identical to the variation in the two benthic morphs of Lake Thingvallavatn. The results are consistent with a scenario where parts of the immune systems have diverged substantially among Arctic charr populations in Iceland, after colonizing the island ∼10.000 years ago.The Palsson laboratory is supported by Icelandic Research foundation and the University of Iceland research fund. Icelandic research foundation (grant of excellence: nr 100204011) to S.S. Sigurdsson, A. Palsson, B.K. Kristjansson, Zophonias O. Jonsson and Ian A. Johnston paid for part of this work. Kalina H. Kapralova and Johannes Gudbrandsson were supported by the University of Iceland doctoral fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer ReviewedRitrýnt tímari

Differential gene expression during early development in recently evolved and sympatric Arctic charr morphs

Phenotypic differences between closely related taxa or populations can arise through genetic variation or be environmentally induced, leading to altered transcription of genes during development. Comparative developmental studies of closely related species or variable populations within species can help to elucidate the molecular mechanisms related to evolutionary divergence and speciation. Studies of Arctic charr (Salvelinus alpinus) and related salmonids have revealed considerable phenotypic variation among populations and in Arctic charr many cases of extensive variation within lakes (resource polymorphism) have been recorded. One example is the four Arctic charr morphs in the ∼10,000 year old Lake Thingvallavatn, which differ in numerous morphological and life history traits. We set out to investigate the molecular and developmental roots of this polymorphism by studying gene expression in embryos of three of the morphs reared in a common garden set-up. We performed RNA-sequencing, de-novo transcriptome assembly and compared gene expression among morphs during an important timeframe in early development, i.e., preceding the formation of key trophic structures. Expectedly, developmental time was the predominant explanatory variable. As the data were affected by some form of RNA-degradation even though all samples passed quality control testing, an estimate of 3′-bias was the second most common explanatory variable. Importantly, morph, both as an independent variable and as interaction with developmental time, affected the expression of numerous transcripts. Transcripts with morph effect, separated the three morphs at the expression level, with the two benthic morphs being more similar. However, Gene Ontology analyses did not reveal clear functional enrichment of transcripts between groups. Verification via qPCR confirmed differential expression of several genes between the morphs, including regulatory genes such as AT-Rich Interaction Domain 4A (arid4a) and translin (tsn). The data are consistent with a scenario where genetic divergence has contributed to differential expression of multiple genes and systems during early development of these sympatric Arctic charr morphs.he project was funded by The Icelandic Center for Research (grant number: 100204011) to Sigurður S. Snorrason, Arnar Pálsson, Zophonías O. Jónsson and Bjarni K. Kristjánsson. The University of Iceland Doctoral Fund to Jóhannes Guðbrandsson and University of Iceland research fund to Arnar Pálsson, Sigurður S. Snorrason and Zophonías O. Jónsson. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer Reviewe

Extensive genetic differentiation between recently evolved sympatric Arctic charr morphs

Publisher's version (útgefin grein)The availability of diverse ecological niches can promote adaptation of trophic specializations and related traits, as has been repeatedly observed in evolutionary radiations of freshwater fish. The role of genetics, environment, and history in ecologically driven divergence and adaptation, can be studied on adaptive radiations or populations showing ecological polymorphism. Salmonids, especially the Salvelinus genus, are renowned for both phenotypic diversity and polymorphism. Arctic charr (Salvelinus alpinus) invaded Icelandic streams during the glacial retreat (about 10,000 years ago) and exhibits many instances of sympatric polymorphism. Particularly, well studied are the four morphs in Lake Þingvallavatn in Iceland. The small benthic (SB), large benthic (LB), planktivorous (PL), and piscivorous (PI) charr differ in many regards, including size, form, and life history traits. To investigate relatedness and genomic differentiation between morphs, we identified variable sites from RNA‐sequencing data from three of those morphs and verified 22 variants in population samples. The data reveal genetic differences between the morphs, with the two benthic morphs being more similar and the PL‐charr more genetically different. The markers with high differentiation map to all linkage groups, suggesting ancient and pervasive genetic separation of these three morphs. Furthermore, GO analyses suggest differences in collagen metabolism, odontogenesis, and sensory systems between PL‐charr and the benthic morphs. Genotyping in population samples from all four morphs confirms the genetic separation and indicates that the PI‐charr are less genetically distinct than the other three morphs. The genetic separation of the other three morphs indicates certain degree of reproductive isolation. The extent of gene flow between the morphs and the nature of reproductive barriers between them remain to be elucidated.This project was supported by The Icelandic Center for Research (RANNIS #100204011) to SSS and coworkers, The University of Iceland Doctoral Fund to JG and University of Iceland research fund to AP, SSS and ZOJ.Peer reviewe

Transcriptional dynamics of a conserved gene expression network associated with craniofacial divergence in Arctic charr

Background Understanding the molecular basis of craniofacial variation can provide insights into key developmental mechanisms of adaptive changes and their role in trophic divergence and speciation. Arctic charr (Salvelinus alpinus) is a polymorphic fish species, and, in Lake Thingvallavatn in Iceland, four sympatric morphs have evolved distinct craniofacial structures. We conducted a gene expression study on candidates from a conserved gene coexpression network, focusing on the development of craniofacial elements in embryos of two contrasting Arctic charr morphotypes (benthic and limnetic). Results Four Arctic charr morphs were studied: one limnetic and two benthic morphs from Lake Thingvallavatn and a limnetic reference aquaculture morph. The presence of morphological differences at developmental stages before the onset of feeding was verified by morphometric analysis. Following up on our previous findings that Mmp2 and Sparc were differentially expressed between morphotypes, we identified a network of genes with conserved coexpression across diverse vertebrate species. A comparative expression study of candidates from this network in developing heads of the four Arctic charr morphs verified the coexpression relationship of these genes and revealed distinct transcriptional dynamics strongly correlated with contrasting craniofacial morphologies (benthic versus limnetic). A literature review and Gene Ontology analysis indicated that a significant proportion of the network genes play a role in extracellular matrix organization and skeletogenesis, and motif enrichment analysis of conserved noncoding regions of network candidates predicted a handful of transcription factors, including Ap1 and Ets2, as potential regulators of the gene network. The expression of Ets2 itself was also found to associate with network gene expression. Genes linked to glucocorticoid signalling were also studied, as both Mmp2 and Sparc are responsive to this pathway. Among those, several transcriptional targets and upstream regulators showed differential expression between the contrasting morphotypes. Interestingly, although selected network genes showed overlapping expression patterns in situ and no morph differences, Timp2 expression patterns differed between morphs. Conclusion Our comparative study of transcriptional dynamics in divergent craniofacial morphologies of Arctic charr revealed a conserved network of coexpressed genes sharing functional roles in structural morphogenesis. We also implicate transcriptional regulators of the network as targets for future functional studies.This project was supported by The Icelandic Centre for Research (RANNIS/IRF, grant 100204) and The University of Iceland Research Fund.Peer Reviewe

Bakteríur við hverastrýtur : undan Arnarnesi í Eyjafirði

Undan Arnarnesi í Eyjafirði og neðansjávar eru hverastrýtur sem líta má á sem sjálfstætt vistkerfi og einstakan lífheim. Sýnum frá þessum stað var safnað árið 2005 og hreinræktaðir stofnar frá þeim geymdir á frysti. Í þessu verkefni voru 100 af þessum stofnum rannsakaðir m.t.t. kennigreiningar með því að rækta þá upp, raðgreina og bera þá saman við stofna í GenBank hjá NCBI. Í ræktun tókst að ná upp 17 stofnum á föstu æti en öllum á fljótandi æti. Mögnun erfðaefnis með PCR gekk eftir með 60 stofna, sem voru sendir í Sanger raðgreiningu. Alls náðist að finna samsvörun við 27 stofna og þar af reyndust 13 stofnar ólíkir innbyrðis. Langflestir voru af ættkvíslinni Bacillus eða 21, en einnig greindust stofnar af ættkvíslunum Kocuria, Micrococcus og Pseudoalteromonas. Með þessari greiningu má segja að tilgangi verkefnisins hafi verðið náð en hann var að komast að því hvaða bakteríur væri að finna nærri þessum hverastrýtum. Þessir stofnar sem fundust hafa allir sín sérkenni sem markast af aðlögun þeirra að búsetu við þessar jaðaraðstæður og eru á þann hátt áhugaverðir til frekari rannsókna varðandi lífvirkni þeirra.Off Arnarnes in Eyjafjörður and underwater are hot springs that can be considered as an independent ecosystem and a unique living world. Samples from this site were collected in 2005 and pure-cultured strains from them were stored in the freezer. In this project, 100 of these strains were studied for identity analysis by culturing them, sequencing and comparing them to populations at GenBank at NCBI. In culture, seventeen strains were successfully harvested on solid medium but all on liquid medium. Genetic amplification of the 16S gene with PCR was successful with 60 strains, which were sent for Sanger sequencing. A total of 27 strains were matched, of which 13 were found to be non-inferior strains with each other. The vast majority were from the genera Bacillus or 21, but strains were also distinguished from the genera Kocuria, Micrococcus and Pseudoalteromonas. With this analysis, it can be said that the purpose of the project was achieved, but it was to find out which bacteria are near these hot springs. These strains found all have their own characteristics, which are marked by their adaptation to residence under these marginal conditions and are thus of interest for further research regarding their bioactivity

Skólastjórnun og traust : forprófun mælitækis

Markmið þessarar rannsóknar var að forprófa mælitæki fyrir traust í skólum með tilliti til áreiðanleika og réttmætis. Bandarískt mælitæki fyrir traust kennara var þýtt úr ensku yfir á íslensku. Það var síðan lagt fyrir 271 kennara með lagskiptu slembiúrtaki sem skiptist eftir búsetu. Helstu niðurstöður eru að mælitækið sem nefnt er Omnibus T-vog hafði sömu þáttabyggingu í íslenska úrtakinu og í bandarísku útgáfunni. Þættirnir sem hlóðst á voru: Traust kennara til skólastjóra (TS), traust kennara til annarra kennara (TK) og traust kennara til skjólstæðinga (TNF) þ.e. nemenda og foreldra. Þetta endurspeglaði þær þrjár víddir sem í fræðilegu samhengi hafa verið tengdar við traust kennara. Hugtaksréttmæti mælitækisins telst töluvert vegna mikils samleitniréttmætis við erlenda útgáfu þess. Það sama verður einnig að segja um innihaldsréttmæti þess og með tilliti til þeirra hliða í trausti kennara sem eru á bakvið hvert 26 atriða á mælitækinu. Fylgni á milli þátta er nokkur en einkum þó á milli TK og TNF eða 0,628. Áreiðanleiki mælitækisins var mikill eða 0,929 sem sem eykur líkur á að það skili sambærilegum niðurstöðum í endurteknum mælingum. Hagnýtt gildi rannsóknarinnar er fólgið í því að með Omnibus T- vog er hægt að leggja mat á traust kennara innan tiltekins skóla og í framhaldinu að átta sig á hvar skóinn kreppir í þeim efnum

Thermal Diffusion and Convective Stability

The stability of a two‐component fluid layer subjected to a temperature gradient has been studied, and the associated thermal diffusion separation has been found to exert a large influence even when the separations are small. The most unexpected and perhaps important result is that an instability has been found which can give rise to convection currents even though the density gradient is not adverse. Thus, a system heated from above can become unstable even when the fluid is less dense at the top of the system provided the more dense substance rises to the upper plate. Many measurements of the Soret coefficient could be subject to this instabilitity.NOTXTinfo:eu-repo/semantics/publishe