Search

Diatoms are unicellular eukaryotic phytoplankton that account for approximately 20% of global carbon fixation and 40% of marine primary productivity; thus, they are essential for global carbon biogeochemical cycling and climate. The availability of ten diatom genome sequences has facilitated evolutionary, biological and ecological research over the past decade; however, a complimentary map of the diatom proteome with direct measurements of proteins and peptides is still lacking. Here, we present a proteome map of the model marine diatom Thalassiosira pseudonana using high-resolution mass spectrometry combined with a proteogenomic strategy. In-depth proteomic profiling of three different growth phases and three nutrient-deficient samples identified 9526 proteins, accounting for ~ 81% of the predicted protein-coding genes. Proteogenomic analysis identified 1235 novel genes, 975 revised genes, 104 splice variants and 234 single amino acid variants. Furthermore, our quantitative proteomic analysis experimentally demonstrated that a considerable number of novel genes were differentially translated under different nutrient conditions. These findings substantially improve the genome annotation of T. pseudonana and provide insights into new biological functions of diatoms. This relatively comprehensive diatom proteome catalog will complement available diatom genome and transcriptome data to advance biological and ecological research of marine diatoms.

Phytoplankton have short generation times, flexible reproduction strategies, large population sizes, and high standing genetic diversity, traits that should facilitate rapid evolution under directional selection. We quantified local adaptation of copper tolerance in a population of the diatom Skeletonema marinoi from a mining exposed inlet in the Baltic Sea and in a non-exposed population 100 km away. We hypothesized that mining pollution has driven evolution of elevated copper tolerance in the impacted population of S. marinoi. Assays of 58 strains originating from sediment resting stages revealed no difference in the average tolerance to copper between the two populations. However, variation within populations was greater at the mining site, with three strains displaying hyper-tolerant phenotypes. In an artificial evolution experiment, we used a novel intraspecific metabarcoding locus to track selection and quantify fitness of all 58 strains during co-cultivation in one control and one toxic copper treatment. As expected, the hyper-tolerant strains enabled rapid evolution of copper tolerance in the mining exposed population through selection on available strain diversity. Within 42 days, in each experimental replicate a single strain dominated (30-99% abundance) but different strains dominated the different treatments. The reference population developed tolerance beyond expectations primarily due to slowly developing plastic response in one strain, suggesting that different modes of copper tolerance are present in the two populations. Our findings provide novel empirical evidence that standing genetic diversity of phytoplankton resting stage allows populations to evolve rapidly (20-50 generations) and flexibly on timescales relevant for seasonal bloom progressions.

Evolutionary changes in populations of microbes, such as microalgae, cannot be traced using conventional metabarcoding loci as they lack intraspecific resolution. Consequently, selection and competition processes amongst strains of the same species cannot be resolved without elaborate isolation, culturing, and genotyping efforts. Bamboozle, a new bioinformatic tool introduced here, scans a species’ entire genome and identifies allele-rich barcodes that enable direct identification of different strains from a common population, and a single DNA sample, using amplicon sequencing. We demonstrate its usefulness by identifying hypervariable barcoding loci (Skeletonema marinoi, and the haploid chlorophyteChlamydomonas reinhardtii. Across the genomes, only 26 loci capable of resolving all available strains’ genotypes were identified, all of which are within protein-coding genes of variable metabolic function. Single nucleotide polymorphisms (SNPs) provided the most reliable genetic markers, and amongst 55 strains ofS. marinoi,three 500 bp loci contained, on average, 46 SNPs, 103 unique alleles, and displayed 100% heterozygosity. The prevalence of heterozygosity was identified as a novel opportunity to improve strain quantification and detect false positive artefacts during denoising of amplicon sequences. Finally, we illustrate how metabarcoding of a single genetic locus can be used to track strain abundances of 58 strains ofS. marinoiin an artificial selection experiment. As future genomics datasets become available and DNA sequencing technologies develop, Bamboozle has flexible user settings enabling optimal barcodes to be designed for other species and applications.

Funder: Fondation Ernst et Lucie Schmidheiny; Id: http://dx.doi.org/10.13039/501100007636, Funder: International Association for Plant Taxonomy; Id: http://dx.doi.org/10.13039/501100020652, Funder: International Palm Society, Funder: Swiss Systematics Society, Aim: Central America is largely covered by hyperdiverse, yet poorly understood, rain forests. Understorey palms are diverse components of these forests, but little is known about their historical assembly. It is not clear when palms in Central America reached present diversity levels and whether most species arrived from neighbouring regions or evolved locally. We addressed these questions using the most species‐rich American palm clades indicative of rain forests. We reconstructed and compared their phylogenomic and biogeographical history with the diversification of 54 other plant lineages, to gain a better understanding of the processes that shaped the assembly of Central American rain forests. Location: Central America. Time period: Cretaceous to present. Major taxa studied: Arecaceae: Arecoideae: Bactridinae, Chamaedoreeae, Geonomateae. Methods: We sampled 218 species through fieldwork and living collections. We sequenced their genomic DNA using target sequence‐capture procedures. Using 12 calibration points, we reconstructed dated phylogenies under three approaches (multispecies coalescent, maximum likelihood and Bayesian inference), conducted biogeographical analyses (dispersal–extinction–cladogenesis) and estimated phylogenetic diversity metrics. Results: Dated phylogenies revealed intense diversification in Central America from 12 Ma. Local diversification events were four times more frequent than dispersal events, and we found strong phylogenetic clustering in relationship to Central America. Main conclusions: Our results suggest that most understorey palm species that characterize the Central American rain forests today evolved locally after repeated dispersal events, mostly from South America. Understorey palms in Central American rain forests diversified primarily after closure of the Central American Seaway at c. 13 Ma, suggesting that the Great American Biotic Interchange was a major trigger for plant diversification in Central American rain forests. This recent diversification contrasts with the much earlier existence of rain forest palms in neighbouring South America since c. 58 Ma. We found similar timings of diversification in 54 other seed plant lineages, suggesting an unexpectedly recent assembly of the hyperdiverse Central American flora.

MSALigMap (Multiple Sequence Alignment Ligand Mapping) is a tool for mapping active-site amino-acid residues that bind selected ligands on to target protein sequences of interest. Users can also provide novel sequences (unavailable in public databases) for analysis. MSALigMap is written in Python. There are several tools and servers available for comparing and mapping active-site amino-acid residues among protein structures. However, there has not previously been a tool for mapping ligand binding amino-acid residues onto protein sequences of interest. Using MSALigMap, users can compare multiple protein sequences, such as those from different organisms or clinical strains, with sequences of proteins with crystal structures in PDB that are bound with the ligand/drug and DNA of interest. This allows users to easily map the binding residues and to predict the consequences of different mutations observed in the binding site. The MSALigMap server can be accessed at https://albiorix.bioenv.gu.se/MSALigMap/HomePage.py.

Interaction between protein and ligands are ubiquitous in a biological cell, and understanding these interactions at the atom level in protein-ligand complexes is crucial for structural bioinformatics and drug discovery. Here, we present a web-based protein-ligand interaction application named Ligand Binding Site Comparison (LiBiSCo) for comparing the amino acid residues interacting with atoms of a ligand molecule between different protein-ligand complexes available in the Protein Data Bank (PDB) database. The comparison is performed at the ligand atom level irrespectively of having binding site similarity or not between the protein structures of interest. The input used in LiBiSCo is one or several PDB IDs of protein-ligand complex(es) and the tool returns a list of identified interactions at ligand atom level including both bonded and non-bonded interactions. A sequence profile for the interaction for each ligand atoms is provided as a WebLogo. The LiBiSco is useful in understanding ligand binding specificity and structural promiscuity among families that are structurally unrelated. The LiBiSCo tool can be accessed through https://albiorix.bioenv.gu.se/LiBiSCo/HomePage.py.

Understanding the genetic regulatory code governing gene expression is an important challenge in molecular biology. However, how individual coding and non-coding regions of the gene regulatory structure interact and contribute to mRNA expression levels remains unclear. Here we apply deep learning on over 20,000 mRNA datasets to examine the genetic regulatory code controlling mRNA abundance in 7 model organisms ranging from bacteria to Human. In all organisms, we can predict mRNA abundance directly from DNA sequence, with up to 82% of the variation of transcript levels encoded in the gene regulatory structure. By searching for DNA regulatory motifs across the gene regulatory structure, we discover that motif interactions could explain the whole dynamic range of mRNA levels. Co-evolution across coding and non-coding regions suggests that it is not single motifs or regions, but the entire gene regulatory structure and specific combination of regulatory elements that define gene expression levels., Regulatory and coding regions of genes are shaped by evolution to control expression levels. Here, the authors use deep learning to identify rules controlling gene expression levels and suggest that all parts of the gene regulatory structure interact in this.

Why, in facultative asexual species, marginal populations are often richer in clones than are core populations, remains unclear. Cloning freezes genotypes but hampers recombination and local adaptation. During expansion, clones are favoured over non-selfing sexuals by uniparental reproduction. To better understand the dynamics of clones and sexual lineage, we used genome-wide sequencing to analyse a recently expanded seaweed. We found large clones and sexual populations mixed close to range margins. Clones had evolved repeatedly from sexual populations but were unexpectedly low in genetic variation. Modelling suggested clones form from sexual populations after repeated bottlenecks at the expansion front. A clonal wave of depauperate genotypes thereafter spread ahead of the sexual population. As we observed, these early formed clones may survive side-by-side sexual individuals, which suggests they lost their sexual capacity. Our study illustrates how range expansion can result in complex and dynamic patterns of genetic variation in facultative asexual species.TeaserWe use genome data and modelling to find out why large clones are only found at range margins in a recently expanded seaweed

BackgroundThe Andean Fever tree (Cinchona L.; Rubiaceae) is the iconic source of bioactive quinine alkaloids, which have been vital to treating malaria for centuries. C. pubescens Vahl, in particular, has been an essential source of income for several countries within its native range in north-western South America. However, an absence of available genomic resources is essential for placing the Cinchona species within the tree of life and setting the foundation for exploring the evolution and biosynthesis of quinine alkaloids.FindingsWe address this gap by providing the first highly contiguous and annotated nuclear and organelle genome assemblies for C. pubescens. Using a combination of ∼120 Gb of long sequencing reads derived from the Oxford Nanopore PromethION platform and 142 Gb of short-read Illumina data. Our nuclear genome assembly comprises 603 scaffolds comprising a total length of 904 Mb, and the completeness represents ∼85% of the genome size (1.1 Gb/1C). This draft genome sequence was complemented by annotating 72,305 CDSs using a combination of de novo and reference-based transcriptome assemblies. Completeness analysis revealed that our assembly is moderately complete, displaying 83% of the BUSCO gene set and a small fraction of genes (4.6%) classified as fragmented. Additionally, we report C. pubescens plastome with a length of ∼157 Kb and a GC content of 37.74%. We demonstrate the utility of these novel genomic resources by placing C. pubescens in the Gentianales order using additional plastid and nuclear datasets.ConclusionsOur study provides the first genomic resource for C. pubescens, thus opening new research avenues, including the provision of crucial genetic resources for analysis of alkaloid biosynthesis in the Fever tree.

Background Triticum aestivum (wheat) is one of the world’s oldest crops and has been used for >8000 years as a food crop in North Africa, West Asia and Europe. Today, wheat is one of the most important sources of grain for humans, and is cultivated on greater areas of land than any other crop. As the human population increases and soil salinity becomes more prevalent, there is increased pressure on wheat breeders to develop salt-tolerant varieties in order to meet growing demands for yield and grain quality. Here we developed a mutant wheat population using the moderately salt-tolerant Bangladeshi variety BARI Gom-25, with the primary goal of further increasing salt tolerance. Results After titrating the optimal ethyl methanesulfonate (EMS) concentration, ca 30,000 seeds were treated with 1% EMS, and 1676 lines, all originating from single seeds, survived through the first four generations. Most mutagenized lines showed a similar phenotype to BARI Gom-25, although visual differences such as dwarfing, giant plants, early and late flowering and altered leaf morphology were seen in some lines. By developing an assay for salt tolerance, and by screening the mutagenized population, we identified 70 lines exhibiting increased salt tolerance. The selected lines typically showed a 70% germination rate on filter paper soaked in 200 mM NaCl, compared to 0–30% for BARI Gom-25. From two of the salt-tolerant OlsAro lines (OA42 and OA70), genomic DNA was sequenced to 15x times coverage. A comparative analysis against the BARI Gom-25 genomic sequence identified a total of 683,201 (OA42), and 768,954 (OA70) SNPs distributed throughout the three sub-genomes (A, B and D). The mutation frequency was determined to be approximately one per 20,000 bp. All the 70 selected salt-tolerant lines were tested for root growth in the laboratory, and under saline field conditions in Bangladesh. The results showed that all the lines selected for tolerance showed a better salt tolerance phenotype than both BARI Gom-25 and other local wheat varieties tested. Conclusion The mutant wheat population developed here will be a valuable resource in the development of novel salt-tolerant varieties for the benefit of saline farming.

Environmental DNA metabarcoding universal primers targeting the hypervariable region of the 12S rRNA gene

The salinity gradient separating marine and freshwater environments represents a major ecological divide for microbiota, yet the mechanisms by which marine microbes have adapted to and ultimately diversified in freshwater environments are poorly understood. Here, we take advantage of a natural evolutionary experiment: the colonization of the brackish Baltic Sea by the ancestrally marine diatom Skeletonema marinoi. To understand how diatoms respond to low salinity, we characterized transcriptomic responses of S. marinoi grown in a common garden. Our experiment included eight genotypes from source populations spanning the Baltic Sea salinity cline. Changes in gene expression revealed a shared response to salinity across genotypes, where low salinities induced profound changes in cellular metabolism, including upregulation of carbon fixation and storage compound biosynthesis, and increased nutrient demand and oxidative stress. Nevertheless, the genotype effect overshadowed the salinity effect, as genotypes differed significantly in their response, both in the magnitude and direction of gene expression. Intraspecific differences included regulation of transcription and translation, nitrogen metabolism, cell signaling, and aerobic respiration. The high degree of intraspecific variation in gene expression observed here highlights an important but often overlooked source of biological variation associated with how diatoms respond and adapt to environmental change.

Sandy beaches are biogeochemical hotspots that bridge marine and terrestrial ecosystems via the transfer of marine organic matter, such as seaweed (termed wrack). A keystone of this unique ecosystem is the microbial community, which helps to degrade wrack and re-mineralize nutrients. However, little is known about the wrackbed microbiome, its composition, trophic ecology, or how it varies over time and space. Here we characterize the wrackbed microbiome as well as the microbiome of a primary consumer, the seaweed fly Coelopa frigida, and examine how they change along one of the most studied ecological gradients in the world, the transition from the marine North Sea to the brackish Baltic Sea. We found that polysaccharide degraders dominated both the wrackbed and seaweed fly microbiomes but there were still consistent differences between wrackbed and fly samples. Furthermore, we observed a shift in both microbial communities and functionality between the North and Baltic Sea. These shifts were mostly due to changes in the frequency of different groups of known polysaccharide degraders (Proteobacteria and Bacteroidota). We hypothesize that microbes were selected for their abilities to degrade different polysaccharides corresponding to a shift in polysaccharide content in the seaweed communities of the North vs. Baltic Sea. Our results reveal the complexities of both the wracked microbial community, with different groups specialized to different roles, and the cascading trophic consequences of shifts in the near shore algal community.

Diatoms are the dominant phytoplankton in temperate oceans and coastal regions and yet little is known about the genetic basis underpinning their global success. Here, we address this challenge by developing the first phenomic approach for a diatom, screening a collection of randomly mutagenized but identifiably tagged transformants. Based upon their tolerance to temperature extremes, several compromised mutants were identified revealing genes either stress related or encoding hypothetical proteins of unknown function. We reveal one of these hypothetical proteins is a novel putative chloroplast fatty acid transporter whose loss affects several fatty acids including the two omega-3, long-chain polyunsaturated fatty acids - eicosapentaenoic and docosahexaenoic acid, both of which have medical importance as dietary supplements and industrial significance in aquaculture and biofuels. This mutant phenotype not only provides new insights into the fatty acid biosynthetic pathways in diatoms but also highlights the future value of phenomics for revealing specific gene functions in these ecologically important phytoplankton.

Initial efforts to sequence the genome of the marine diatom Skeletonema marinoi were hampered by the presence of genetic material from bacteria, and there was sufficient material from some of these bacteria to enable the assembly of full chromosomes. Here, we report the genome of strain SMS9, one such bacterial species identified in a non-axenic culture of S. marinoi strain ST54. Its 5,482,391 bp circular chromosome contains 4,641 CDSs, and has a G+C content of 35.6%. Based on 16S rRNA comparison, phylotaxonomic analysis, and the genome similarity metrics dDDH and OrthoANI, we place this strain in the genus Kordia, and to the best of our knowledge, this is the first Kordia species to be initially described from European waters. As attempts to culture this strain have failed, however, the specifics of its relationship with S. marinoi are still uncertain.

When studying diatoms, an important consideration is the role of associated bacteria in the diatom-microbiome holobiont. To that end, bacteria isolated from a culture of Skeletonema marinoi strain R05AC were sequenced, one of which being bacterial strain SMR1, presented here. The genome consists of a circular chromosome and seven circular plasmids, totalling 5,121,602 bp. After phylotaxonomic analysis and 16S rRNA sequence comparison, we place this strain in the taxon Sulfitobacter pseudonitzschiae on account of similarity to the type strain. The annotated genome suggests similar interactions between strain SMR1 and its host diatom as have been shown previously in diatom-associated Sulfitobacter, for example bacterial production of growth hormone for its host, and breakdown of diatom-derived DMSP by Sulfitobacter for use as a sulfur source.

Attempts to obtain axenic cultures of the marine diatom Skeletonema marinoi often result in poor growth, indicating the importance of the microbiome to the growth of its host. In order to identify the precise roles played by these associated bacteria, individual strains were isolated, cultured and sequenced. We report the genome of one such strain - SMR5, isolated from a culture of S. marinoi strain R05AC sampled from top layer sediments of the Swedish west coast. Its genome of 4,630,160 bp consists of a circular chromosome and one circular plasmid, and 4,263 CDSs were inferred in the annotation. Comparison of 16S rRNA sequences and other markers, along with phylotaxonomic analysis, leads us to place strain SMR5 in the taxon Marinobacter salarius. Pathway analysis and previous experimental work suggest that this strain may produce a growth factor, as well as improve iron availability for its host via siderophores.

National monitoring programs provide the basis for evaluating the integrity of ecosystems, their responses to disturbances, and the success of actions taken to conserve or recover biodiversity. In this study, we successfully established a national program for the invasive chytrid fungus Batrachochytrium dendrobatidis (Bd) based on dual TaqMan assays. Amphibian diversity based on metabarcoding of the mitochondrial 12S rRNA gene was also performed. Assays were optimized for sensitive detection of target species from a wide range of amphibian ponds with variable potential of inhibitions for eDNA based detection. An amphibian mock community of 5 species was used to validate the metabarcoding approach while internal standards were used in the case of the dual TaqMan assays. First sampling of over 170 ponds in Norway resulted in Bd detection in 12 environmental samples and one swab sample taken over multiple years indicating the establishment of Bd in Norway. Five amphibian species Bufo bufo, Lissotriton vulgaris, Triturus cristatus, Rana arvalis and Rana temporaria as predicted from data in long-term citizen science reporting systems were widely detected in the collected eDNA samples. Our large scale-monitoring program indicates a low risk of a Bd outbreak and amphibian decline caused by chytridiomycosis but continued monitoring is recommended in the future. These findings indicate that eDNA is an effective method to detect invasive species, and to monitor endangered amphibian species. Still, several shortcomings (such as PCR inhibitors and sample volume) were identified that need to be addressed to improve eDNA-based monitoring at the national level.

A species-specific assay was developed and tested by Agersnap et al. (2017) Crayfish play important role in freshwater ecosystems. Noble crayfish "Astacus astacus" is threatened to extinct by non-indigenous species such as signal crayfish "Pacifastacus leniusculus".

The fungus Batrachochytrium dendrobatidis (Bd) was first detected in Norway in 2017, and thus indicate the arrival of an invasive black-listed species in the country. Here we report the details of real time PCR assay which was used to screen for B. dendrobatidis from water samples collected from different locations in Norway.

Environmental DNA metabarcoding universal primers targeting the hypervariable region of the 12S rRNA gene

The fungus Batrachochytrium dendrobatidis (Bd) was first detected in Norway in 2017, and thus indicate the arrival of an invasive black-listed species in the country. Here we report the details of real time PCR assay which was used to screen for B. dendrobatidis from water samples collected from different locations in Norway.

Environmental DNA metabarcoding universal primers targeting the hypervariable region of the 12S rRNA gene

qPCR assay to detect freshwater pearl mussels Margaritifera margaritifera in order to monitor populations in their natural environment.

This protocol explain the qPCR assay for detecting the pathogenic fungus Batrachochytrium dendrobatidis in environmental DNA samples and metabarcoding of amphibians species.

Understanding the genetic regulatory code that governs gene expression is a primary, yet challenging aspiration in molecular biology that opens up possibilities to cure human diseases and solve biotechnology problems. However, the fundamental question of how each of the individual coding and non-coding regions of the gene regulatory structure interact and contribute to the mRNA expression levels remains unanswered. Considering that all the information for gene expression regulation is already present in living cells, here we applied deep learning on over 20,000 mRNA datasets in 7 model organisms ranging from bacteria to Human. We show that in all organisms, mRNA abundance can be predicted directly from the DNA sequence with high accuracy, demonstrating that up to 82% of the variation of gene expression levels is encoded in the gene regulatory structure. Coding and non-coding regions carry both overlapping and orthogonal information and additively contribute to gene expression levels. By searching for DNA regulatory motifs present across the whole gene regulatory structure, we discover that motif interactions can regulate gene expression levels in a range of over three orders of magnitude. The uncovered co-evolution of coding and non-coding regions challenges the current paradigm that single motifs or regions are solely responsible for gene expression levels. Instead, we show that the correct combination of all regulatory regions must be established in order to accurately control gene expression levels. Therefore, the holistic system that spans the entire gene regulatory structure is required to analyse, understand, and design any future gene expression systems.

The bacterial strain SMR4y belongs to the diverse microbiome of the marine diatom Skeletonema marinoi strain R05AC. After assembly of its genome, presented here, and subsequent analyses, we placed it in the genus Sphingorhabdus. This strain has a 3,479,724-bp circular chromosome (with 3,340 coding sequences) and no known plasmids.

Since the beginning of global trade, hundreds of species have colonized territories outside of their native range. Some of these species proliferate at the expense of native ecosystems, i.e., have become invasive. Invasive species constitute powerful in situ experimental systems to study fast adaptation and directional selection on short ecological timescales. They also present promising case studies for ecological and evolutionary success in novel environments.We seize this unique opportunity to study genomic substrates for ecological success and adaptability to novel environments in a vertebrate. We report a highly contiguous long-read based genome assembly for the most successful temperate invasive fish, the benthic round goby (Neogobius melanostomus), and analyse gene families that may promote its impressive ecological success.Our approach provides novel insights from the large evolutionary scale to the small species-specific scale. We describe expansions in specific cytochrome P450 enzymes, a remarkably diverse innate immune system, an ancient duplication in red light vision accompanied by red skin fluorescence, evolutionary patterns in epigenetic regulators, and the presence of genes that may have contributed to the round goby’s capacity to invade cold and salty waters.A recurring theme across all analyzed gene families are gene expansions. This suggests that gene duplications may promote ecological flexibility, superior performance in novel environments, and underlie the impressive colonization success of the round goby. Gobiidae generally feature fascinating adaptations and are excellent colonizers. Further long-read genome approaches across the goby family may reveal whether the ability to conquer new habitats relates more generally to gene copy number expansions.

The bacterial strain SMR4y belongs to the diverse microbiome of the marine diatom Skeletonema marinoi strain R05AC. After assembly of its genome, presented here, and subsequent analyses, we placed it in the genus Sphingorhabdus . This strain has a 3,479,724-bp circular chromosome (with 3,340 coding sequences) and no known plasmids.

Perch (Perca fluviatilis) has been used in biological effect monitoring in a program for integrated coastal fish monitoring at the reference site Kvädöfjärden along the Swedish east coast, which is a site characterized by no or minor local anthropogenic influences. Using a set of physiological and biochemical endpoints (i.e., biomarkers), clear time trends for “early warning” signs of impaired health were noted in the perch from this site, possibly as a result of increased baseline pollution. The data sets also showed relatively large variations among years. To identify additional temporal variation in biological parameters, global mRNA expression studies using RNA sequencing was performed. Perch collected in 2010 and 2014 were selected, as they showed variations in several biomarkers, such as the activity of the detoxification enzyme CYP1A (EROD), the plasma levels of vitellogenin, markers for oxidative stress, white blood cells count and gonad sizes. The RNA sequencing study identified approximately 4800 genes with a significantly difference in mRNA expression levels. A gene ontology enrichment analysis showed that these differentially expressed genes were involved in biological processes such as complement activation, iron ion homeostasis and cholesterol biosynthetic process. In addition, differences in immune system parameters and responses to the exposure of toxic substances have now been verified in two different biological levels (mRNA and protein) in perch collected in 2010 and 2014. Markedly higher mRNA expression of the membrane transporter (MATE) and the detoxification enzyme COMT, together with higher concentrations of bioactive naturally produced brominated compounds, such as brominated indoles and carbazoles, seem to indicate that the perch collected in 2014 had been exposed to macro- and microalga blooming to a higher degree than did perch from 2010. These results and the differential mRNA expression between the 2 years in genes related to immune and oxidative stress parameters suggest that attention must be given to algae blooming when elucidating the well-being of the perch at Kvädöfjärden and other Baltic coastal sites.

Sexual reproduction plays a fundamental role in diatom life cycles. It contributes to increasing genetic diversity through meiotic recombination and also represents the phase where large-sized cells are produced to counteract the cell size reduction process that characterizes these microalgae. With the aim to identify genes linked to the sexual phase of the centric planktonic diatom Skeletonema marinoi, we carried out an RNA-seq experiment comparing the expression level of transcripts in sexualized cells with that of large cells not competent for sex. A set of genes involved in meiosis were found upregulated. Despite the fact that flagellate gametes were observed in the sample, we did not detect the expression of genes involved in the synthesis of flagella that were upregulated during sexual reproduction in another centric diatom. A comparison with the set of genes changing during the first phases of sexual reproduction of the pennate diatom Pseudo-nitzschia multistriata revealed the existence of commonalities, including the strong upregulation of genes with an unknown function that we named Sex Induced Genes (SIG). Our results further broadened the panel of genes that can be used as a marker for sexual reproduction of diatoms, crucial for the interpretation of metatranscriptomic datasets.

Introduction Chloroplasts are plant organelles responsible for the bulk of terrestrial photosynthetic primary production. They evolved via endosymbiosis from a cyanobacterial organism more than a billion years ago. The biogenesis and operation of chloroplasts depends on the assembly and homeostasis of thousands of nucleus-encoded proteins, which together constitute a large part of the organellar proteome. These proteins are imported by multiprotein translocases in each of the chloroplast envelope membranes after translation in the cytosol. Chloroplast proteins are subject to proteolytic regulation, which plays vital roles in maintaining normal organellar functions and in delivering responses to developmental and environmental cues. Turnover of internal chloroplast proteins is controlled by proteases inherited from the organelle’s prokaryotic ancestor, but mechanisms underlying the degradation of chloroplast outer envelope membrane (OEM) proteins are poorly defined. Rationale We previously showed that components of the protein import translocases in the OEM (so-called TOC proteins) are ubiquitinated by the OEM-localized ubiquitin E3 ligase SP1 and subsequently degraded by the cytosolic 26S proteasome. Inherent in this process is a need to extricate the target proteins from the chloroplast membrane (they are integral membrane proteins), and to achieve this there must exist mechanisms to overcome the physical and thermodynamic barriers to extraction. This implies that additional factors are involved in OEM protein degradation, and we sought to identify these by applying forward genetics and proteomic analysis in the plant Arabidopsis. Results We identified two factors required for the degradation of chloroplast OEM proteins: SP2 and CDC48. The former is an Omp85-type β-barrel channel of prokaryotic origin located in the OEM, and the latter is a conserved eukaryotic AAA+ chaperone located in the cytosol. We observed that inactivation of either component triggers the selective overaccumulation of target proteins, specifically at the chloroplast envelope. We used genetic analyses to demonstrate that SP2 and CDC48 act together in the same proteolytic pathway as the SP1 E3 ligase and physical interaction studies to show that the three components can form a complex at the surface of the chloroplast. Furthermore, by applying complementary in vivo and in vitro assays, we demonstrated that the SP2 and CDC48 proteins cooperate to bring about the extraction (“retrotranslocation”) of ubiquitinated proteins from the OEM. Overall, the data are consistent with a model (see the figure) in which SP2 and CDC48 fulfil conductance and motor functions, respectively, in the retrotranslocation of OEM proteins ubiquitinated by SP1 to enable their proteasomal degradation in the cytosol. These results extend the range of known functions of Omp85 superfamily proteins (which heretofore included bacterial protein secretion, membrane protein biogenesis, and organelle protein import) and of CDC48 (which has a well-characterized role in endoplasmic reticulum–associated protein degradation). The broader importance of this proteolytic mechanism was demonstrated by physiological analyses of plants with altered SP2 activity, which revealed defects in organellar functions, plant development, and viability. Conclusion Collectively, our results describe a multicomponent system for chloroplast envelope protein removal, dependent on the cytosolic ubiquitin-proteasome system, which is critically important for plant growth. A key part of the system is a protein retrotranslocation mechanism of chimeric prokaryotic-eukaryotic ancestry that operates at the surface of the organelle. We refer to this proteolytic system as chloroplast-associated protein degradation, or CHLORAD.

Arenibacter algicola strain SMS7 was isolated from a culture of the marine diatom Skeletonema marinoi strain ST54, sampled from top-layer sediments in Kosterfjord, Sweden. Here, we present its 5,857,781-bp genome, consisting of a circular chromosome and one circular plasmid, in all containing 4,932 coding sequences.

Recent molecular studies have identified substantial fungal diversity in indoor environments. Fungi and fungal particles have been linked to a range of potentially unwanted effects in the built environment, including asthma, decay of building materials, and food spoilage. The study of the built mycobiome is hampered by a number of constraints, one of which is the poor state of the metadata annotation of fungal DNA sequences from the built environment in public databases. In order to enable precise interrogation of such data – for example, “retrieve all fungal sequences recovered from bathrooms” – a workshop was organized at the University of Gothenburg (May 23-24, 2016) to annotate public fungal barcode (ITS) sequences according to the MIxS-Built Environment annotation standard (http://gensc.org/mixs/). The 36 participants assembled a total of 45,488 data points from the published literature, including the addition of 8,430 instances of countries of collection from a total of 83 countries, 5,801 instances of building types, and 3,876 instances of surface-air contaminants. The results were implemented in the UNITE database for molecular identification of fungi (http://unite.ut.ee) and were shared with other online resources. Data obtained from human/animal pathogenic fungi will furthermore be verified on culture based metadata for subsequent inclusion in the ISHAM-ITS database (http://its.mycologylab.org).