Dual RNA-Seq Uncovers Metabolic Amino Acids Dependency of the Intracellular Bacterium Piscirickettsia salmonis Infecting Atlantic Salmon

High-throughput sequencing technologies have offered the possibility to understand the complexity of the transcriptomic responses of an organism during a wide variety of biological scenarios, such as the case of pathogenic infections. Recently, the simultaneous sequencing of both pathogen and host transcriptomes (dual RNA-seq) during the infection has become a promising approach to uncover the complexity of the host–pathogen interactions. In this study, through a double rRNA depletion and RNA sequencing protocols, we simultaneously analyzed the transcriptome of the intracellular bacterium Piscirickettsia salmonis and its host the Atlantic salmon (Salmo salar) during the course of the infection. Beyond canonical host immune-related response and pathogen virulent factors, both bacteria and host displayed a large number of genes associated with metabolism and particularly related with the amino acid metabolism. Notably, genome-wide comparison among P. salmonis genomes and different fish pathogens genomes revealed a lack of the biosynthetic pathway for several amino acids such as valine, leucine, and isoleucine. To support this finding, in vitro experiments evidenced that when these amino acids are restricted the bacterial growth dynamics is significantly affected. However, this condition is phenotypically reversed when the amino acids are supplemented in the bacterial growth medium. Based on our results, a metabolic dependency of P. salmonis on S. salar amino acids is suggested, which could imply novel mechanisms of pathogenesis based on the capacity to uptake nutrients from the host. Overall, dual transcriptome sequencing leads to the understanding of host–pathogen interactions from a different perspective, beyond biological processes related to immunity

Long noncoding RNAs: unexplored players in the drug response of the sea louse Caligus rogercresseyi

Long non-coding RNAs (lncRNAs), endogenous RNAs with restricted or null coding potential, are emerging as key regulators of multiple biological processes in several species. Despite the importance of these transcripts, few studies have characterized marine crustacean lncRNAs or the modulation of these in response to chemical exposure. Therefore, the present study mainly focused on identifying lncRNAs in the sea louse Caligus rogercresseyi, an ectoparasite of primary concern to the Chilean salmon industry. A bioinformatics pipeline for lncRNAs discovery was designed, revealing 1835 putative lncRNA sequences in the C. rogercresseyi transcriptome. Furthermore, C. rogercresseyi lncRNAs evidenced features classical of lncRNAs, such as lower values of GC content, length, transcription activity, and minimum free energy as compared with coding transcripts. Furthermore, since developed resistance against delousing drugs is a major threat to the management and control of sea lice, the transcriptional modulation of C. rogercresseyi lncRNAs during exposure to delousing drugs was also evaluated. Unlike coding transcripts, lncRNAs were mainly downregulated after exposure to either deltamethrin or azamethiphos, showing transcription patterns similar to other, better studied non-coding RNAs in arthropods. Finally, a subset of lncRNAs exhibited a strong transcriptional correlation to genes commonly associated with the drug response, such as ABC transporters, cytochrome p450, and glutathione S-transferase, among others. Our findings provide one of the first comprehensive lncRNA characterizations in a crustacean, contributing towards understandings on the regulatory role of lncRNAs during the drug response in Caligus rogercresseyi

The Atlantic salmon (Salmo salar) antimicrobial peptide cathelicidin-2 is a molecular host-associated cue for the salmon louse (Lepeophtheirus salmonis)

Chemical signals are a key element of host-parasite interactions. In marine ecosystems, obligate ectoparasites, such as sea lice, use chemical cues and other sensory signals to increase the probability of encountering a host and to identify appropriate hosts on which they depend to complete their life cycle. The chemical compounds that underlie host identification by the sea lice are not fully described or characterized. Here, we report a novel compound - the Atlantic salmon (Salmo salar) antimicrobial peptide cathelicidin-2 (Cath-2) – that acts as an activation cue for the marine parasitic copepod Lepeophtheirus salmonis. L. salmonis were exposed to 0, 7, 70 and 700 ppb of Cath-2 and neural activity, swimming behaviour and gene expression profiles of animals in response to the peptide were evaluated. The neurophysiological, behavioural and transcriptomic results were consistent: L. salmonis detects Cath-2 as a water-soluble peptide released from the skin of salmon, triggering chemosensory neural activity associated with altered swimming behaviour of copepodids exposed to the peptide, and chemosensory-related genes were up-regulated in copepodids exposed to the peptide. L. salmonis are activated by Cath-2, indicating a tight link between this peptide and the salmon louse chemosensory system.publishedVersio

Whole-genome resequencing in the sea louse Caligus rogercresseyi uncovers gene duplications and copy number variants associated with pesticide resistance

The sea louse Caligus rogercresseyi is a marine ectoparasite that constitutes one of the major threats to the salmon farming industry, where the primary control strategy is the use of delousing drugs through immersion treatments. The emergence of pharmacological resistance in this copepodid species has previously been described using transcriptome data. However, the molecular mechanisms underlying chromosome rearrangements have not yet been explored. This study aimed to identify structural genomic variations and gene expression in C. rogercresseyi associated with pesticide sensitivity. In this study, genome resequencing was conducted using Oxford Nanopore Technology on lice strains with contrasting sensitivity to azamethiphos to detect genome duplications. Transcriptome profiling of putative gene duplications was performed by Illumina sequencing. Copy Number Variants (CNVs) were identified through comparative coverage, and collinear/tandem gene duplications over all the chromosomal regions by sequence homology. Duplications or CNVs in functional genes were primarily identified in transposable elements and genes related to the drug response, with differential expression values calculated by RNA-seq analyses of the same strains. Notably, differentially duplicated genes were found in coding regions related to cuticle proteins, suggesting that a putative resistance mechanism may be associated with cuticular structure formation and the proteins involved. Collectively, the results revealed that the intensive use of pesticides on sea lice populations increases the frequency of gene duplication, expanding the molecular elements involved in drug response. This study is the first to report an association between genome rearrangements and pharmacological resistance in sea lice populations

A multidisciplinary approach to identify pelagic shark fins by molecular, morphometric and digital correlation data

Accurate species identification is one of the most important issues to conserve and manage shark fisheries. A multidisciplinary approach involving molecular (using variation at ITS2 sequences), morphometrical and image processing species identification was performed to evaluate their discriminating power with three pelagic shark species common to the coasts of Chile (Prionace glauca Linnaeus 1785, Isurus oxyrinchus Rafinesque 1810, and Lamna nasus (Bonnaterre, 1788). Species-specific DNA markers and multivariate analyses based on twenty morphometrical measurements were used to identify fresh and dry fin sets for each shark species. Additionally, coloring patterns and fin shape were jointly used to distinguish dry fin sets of shark species by using digital invariant correlation (relation target and problem image independent of their changes in position, scale and rotation). Our results showed that morphometrical analysis was the least accurate approach, whereas DNA-based identification and image processing approaches were 100% successful on the identification of shark species. Thus ITS2 sequences and morphological diagnostic characteristics such as the ones related to color patterns, allow the correct identification of shark species. Therefore, the implementation of molecular and/or image tools can be applied to confidently identify the main pelagic shark species involved in Chilean landing and fin trade.Accurate species identification is one of the most important issues to conserve and manage shark fisheries. A multidisciplinary approach involving molecular (using variation at ITS2 sequences), morphometrical and image processing species identification was performed to evaluate their discriminating power with three pelagic shark species common to the coasts of Chile (Prionace glauca Linnaeus 1785, Isurus oxyrinchus Rafinesque 1810, and Lamna nasus (Bonnaterre, 1788). Species-specific DNA markers and multivariate analyses based on twenty morphometrical measurements were used to identify fresh and dry fin sets for each shark species. Additionally, coloring patterns and fin shape were jointly used to distinguish dry fin sets of shark species by using digital invariant correlation (relation target and problem image independent of their changes in position, scale and rotation). Our results showed that morphometrical analysis was the least accurate approach, whereas DNA-based identification and image processing approaches were 100% successful on the identification of shark species. Thus ITS2 sequences and morphological diagnostic characteristics such as the ones related to color patterns, allow the correct identification of shark species. Therefore, the implementation of molecular and/or image tools can be applied to confidently identify the main pelagic shark species involved in Chilean landing and fin trade

Chromosome-Level Genome Assembly of the Blue Mussel Mytilus chilensis Reveals Molecular Signatures Facing the Marine Environment

The blue mussel Mytilus chilensis is an endemic and key socioeconomic species inhabiting the southern coast of Chile. This bivalve species supports a booming aquaculture industry, which entirely relies on artificially collected seeds from natural beds that are translocated to diverse physical–chemical ocean farming conditions. Furthermore, mussel production is threatened by a broad range of microorganisms, pollution, and environmental stressors that eventually impact its survival and growth. Herein, understanding the genomic basis of the local adaption is pivotal to developing sustainable shellfish aquaculture. We present a high-quality reference genome of M. chilensis, which is the first chromosome-level genome for a Mytilidae member in South America. The assembled genome size was 1.93 Gb, with a contig N50 of 134 Mb. Through Hi-C proximity ligation, 11,868 contigs were clustered, ordered, and assembled into 14 chromosomes in congruence with the karyological evidence. The M. chilensis genome comprises 34,530 genes and 4795 non-coding RNAs. A total of 57% of the genome contains repetitive sequences with predominancy of LTR-retrotransposons and unknown elements. Comparative genome analysis of M. chilensis and M. coruscus was conducted, revealing genic rearrangements distributed into the whole genome. Notably, transposable Steamer-like elements associated with horizontal transmissible cancer were explored in reference genomes, suggesting putative relationships at the chromosome level in Bivalvia. Genome expression analysis was also conducted, showing putative genomic differences between two ecologically different mussel populations. The evidence suggests that local genome adaptation and physiological plasticity can be analyzed to develop sustainable mussel production. The genome of M. chilensis provides pivotal molecular knowledge for the Mytilus complex

The wastewater microbiome: a novel insight for COVID-19 surveillance

Wastewater-Based Epidemiology is a tool to face and mitigate COVID-19 outbreaks by evaluating conditions in a specic community. This study aimed to analyze the microbiome proles using nanopore technology for full-length 16S rRNA sequencing in wastewater samples collected from a penitentiary (P), a residential care home (RCH), and a quarantine or health care facilities (HCF). The HCF microbiome was strongly associated with enteric bacteria previously reported in patients with chronic disease and psychological disorders. During the study, the wastewater samples from the RCH and the P were negative for SARS-CoV-2 based on qPCRs, except during the fourth week when was detected. Unexpectedly, the wastewater microbiome from RCH and P prior to week four was correlated with the samples collected from the HCF, suggesting a core bacterial community is expelled from the digest tract of individuals infected with SARS-CoV-2. We provide novel evidence that the wastewater microbiome associated with gastrointestinal manifestations appears to precede the SARS-CoV-2 detection in sewage. This nding suggests that the wastewaters microbiome can be applied as an indicator of community-wide SARS-CoV2 surveillance.This study was funded by “Fondo de Emergencia Sanitaria COVID-19, Intendencia Región de Ñuble, Chile” and FONDAP #15110027 granted by National Research and Development Agency (ANID), Chile. We also thank MINSAL and MinCiencia to support this research and provide the epidemiological data.N

Data from: SNP discovery and high resolution melting analysis from massive transcriptome sequencing in the California red abalone Haliotis rufescens

The California red abalone, Haliotis rufescens that belongs to the Haliotidae family, is the largest species of abalone in the world that has sustained the major fishery and aquaculture production in the USA and Mexico. This native mollusk has not been evaluated or assigned a conservation category even though in the last few decades it was heavily exploited until it disappeared in some areas along the California coast. In Chile, the red abalone was introduced in the 1970's from California wild abalone stocks for the purposes of aquaculture. Considering the number of years that the red abalone has been cultivated in Chile crucial genetic information is scarce and critical issues remain unresolved. This study reports and validates novel single nucleotide polymorphisms (SNP) markers for the red abalone H. rufescens using cDNA pyrosequencing. A total of 622 high quality SNPs were identified in 146 sequences with an estimated frequency of 1 SNP each 1,000 bp. Forty-five SNPs markers with functional information for gene ontology were selected. Of these, 8 were polymorphic among the individuals screened: Heat shock protein 70 (HSP70), vitellogenin (VTG), lysin, Alginate lyase enzyme (AL), Glucose-regulated protein 94 (GRP94), fructose-bisphosphate aldolase (FBA), sulfatase 1A precursor (S1AP) and ornithine decarboxylase antizyme (ODC). Two additional sequences were also identified with polymorphisms but no similarities with known proteins were achieved. To validate the putative SNP markers, High Resolution Melting Analysis (HRMA) was conducted in a wild and hatchery-bred population. Additionally, SNP cross-amplifications were tested in two further native abalone species, H. fulgens and H. corrugata. This study provides novel candidate genes that could be used to evaluate loss of genetic diversity due to hatchery selection or inbreeding effects

SNP_Hr_astringente

Fasta file with assembled sequences used for SNP minin