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Comparative analysis of expressed sequence tag (EST) libraries in the seagrass Zostera marina subjected to temperature stress.

ABSTRACT: Global warming is associated with increasing stress and mortality on temperate seagrass beds, in particular during periods of high sea surface temperatures during summer months, adding to existing anthropogenic impacts, such as eutrophication and habitat destruction. We compare several expressed sequence tag (EST) in the ecologically important seagrass Zostera marina (eelgrass) to elucidate the molecular genetic basis of adaptation to environmental extremes. We compared the tentative unigene (TUG) frequencies of libraries derived from leaf and meristematic tissue from a control situation with two experimentally imposed temperature stress conditions and found that TUG composition is markedly different among these conditions (all P < 0.0001). Under heat stress, we find that 63 TUGs are differentially expressed (d.e.) at 25 degrees C compared with lower, no-stress condition temperatures (4 degrees C and 17 degrees C). Approximately one-third of d.e. eelgrass genes were characteristic for the stress response of the terrestrial plant model Arabidopsis thaliana. The changes in gene expression suggest complex photosynthetic adjustments among light-harvesting complexes, reaction center subunits of photosystem I and II, and components of the dark reaction. Heat shock encoding proteins and reactive oxygen scavengers also were identified, but their overall frequency was too low to perform statistical tests. In all conditions, the most abundant transcript (3-15%) was a putative metallothionein gene with unknown function. We also find evidence that heat stress may translate to enhanced infection by protists. A total of 210 TUGs contain one or more microsatellites as potential candidates for gene-linked genetic markers. Data are publicly available in a user-friendly database at http://www.uni-muenster.de/Evolution/ebb/Services/zostera .

SUBMITTER: Reusch TB

PROVIDER: S-EPMC2757623 | biostudies-literature | 2008 May-Jun

REPOSITORIES: biostudies-literature

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Comparative analysis of expressed sequence tag (EST) libraries in the seagrass Zostera marina subjected to temperature stress.

Reusch Thorsten B H TB Veron Amelie S AS Preuss Christoph C Weiner January J Wissler Lothar L Beck Alfred A Klages Sven S Kube Michael M Reinhardt Richard R Bornberg-Bauer Erich E

Marine biotechnology (New York, N.Y.) 20080118 3

Global warming is associated with increasing stress and mortality on temperate seagrass beds, in particular during periods of high sea surface temperatures during summer months, adding to existing anthropogenic impacts, such as eutrophication and habitat destruction. We compare several expressed sequence tag (EST) in the ecologically important seagrass Zostera marina (eelgrass) to elucidate the molecular genetic basis of adaptation to environmental extremes. We compared the tentative unigene (TU ...[more]

PMID: 18239962

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Project description:Seagrasses are globally distributed marine flowering plants that are foundation species in coastal ecosystems. Seagrass beds play essential roles as habitats and hatcheries, in nutrient cycling, and in protecting the coastline from erosion. Although many studies have focused on seagrass ecology, only a limited number have investigated their associated fungi. In terrestrial systems, fungi can have beneficial and detrimental effects on plant fitness. However, not much is known about marine fungi and even less is known about seagrass associated fungi. Here we used culture-independent sequencing of the ribosomal internal transcribed spacer (ITS) region to characterize the taxonomic diversity of fungi associated with the seagrass, Zostera marina. We sampled from two Z. marina beds in Bodega Bay over three time points to investigate fungal diversity within and between plants. Our results indicate that there are many fungal taxa for which a taxonomic assignment cannot be made living on and inside Z. marina leaves, roots and rhizomes and that these plant tissues harbor distinct fungal communities. We also identified differences in the abundances of the orders, Glomerellales, Agaricales and Malasseziales, between seagrass tissues. The most prevalent ITS amplicon sequence variants (ASVs) associated with Z. marina tissues could not initially be confidently assigned to a fungal phylum, but shared significant sequence similarity with Chytridiomycota and Aphelidomycota. To obtain a more definitive taxonomic classification of the most abundant ASV associated with Z. marina leaves, we used PCR with one primer targeting a unique region of this ASV's ITS2 and a second primer targeting fungal 28S rRNA genes to amplify part of the 28S rRNA gene region corresponding to this ASV. Sequencing and phylogenetic analysis of the resulting partial 28S rRNA gene revealed that the organism that this ASV comes from is a member of Novel Clade SW-I in the order Lobulomycetales in the phylum Chytridiomycota. This clade includes known parasites of freshwater diatoms and algae and it is possible this chytrid is directly infecting Z. marina leaf tissues. This work highlights a need for further studies focusing on marine fungi and the potential importance of these understudied communities to the larger seagrass ecosystem.

Project description:Background: Seagrasses (Alismatales) are the only fully marine angiosperms. Zostera marina (eelgrass) plays a crucial role in the functioning of coastal marine ecosystems and global carbon sequestration. It is the most widely studied seagrass and has become a marine model system for exploring adaptation under rapid climate change. The original draft genome (v.1.0) of the seagrass Z. marina (L.) was based on a combination of Illumina mate-pair libraries and fosmid-ends. A total of 25.55 Gb of Illumina and 0.14 Gb of Sanger sequence was obtained representing 47.7× genomic coverage. The assembly resulted in ~2000 unordered scaffolds (L50 of 486 Kb), a final genome assembly size of 203MB, 20,450 protein coding genes and 63% TE content. Here, we present an upgraded chromosome-scale genome assembly and compare v.1.0 and the new v.3.1, reconfirming previous results from Olsen et al. (2016), as well as pointing out new findings. Methods: The same high molecular weight DNA used in the original sequencing of the Finnish clone was used. A high-quality reference genome was assembled with the MECAT assembly pipeline combining PacBio long-read sequencing and Hi-C scaffolding. Results: In total, 75.97 Gb PacBio data was produced. The final assembly comprises six pseudo-chromosomes and 304 unanchored scaffolds with a total length of 260.5Mb and an N50 of 34.6 MB, showing high contiguity and few gaps (~0.5%). 21,483 protein-encoding genes are annotated in this assembly, of which 20,665 (96.2%) obtained at least one functional assignment based on similarity to known proteins. Conclusions: As an important marine angiosperm, the improved Z. marina genome assembly will further assist evolutionary, ecological, and comparative genomics at the chromosome level. The new genome assembly will further our understanding into the structural and physiological adaptations from land to marine life.

Project description:BackgroundThe seagrass Zostera marina is a monocotyledonous angiosperm belonging to a polyphyletic group of plants that can live submerged in marine habitats. Zostera marina L. is one of the most common seagrasses and is considered a cornerstone of marine plant molecular ecology research and comparative studies. However, the mechanisms underlying its adaptation to the marine environment still remain poorly understood due to limited transcriptomic and genomic data.Principal findingsHere we explored the transcriptome of Z. marina leaves under different environmental conditions using Illumina paired-end sequencing. Approximately 55 million sequencing reads were obtained, representing 58,457 transcripts that correspond to 24,216 unigenes. A total of 14,389 (59.41%) unigenes were annotated by blast searches against the NCBI non-redundant protein database. 45.18% and 46.91% of the unigenes had significant similarity with proteins in the Swiss-Prot database and Pfam database, respectively. Among these, 13,897 unigenes were assigned to 57 Gene Ontology (GO) terms and 4,745 unigenes were identified and mapped to 233 pathways via functional annotation against the Kyoto Encyclopedia of Genes and Genomes pathway database (KEGG). We compared the orthologous gene family of the Z. marina transcriptome to Oryza sativa and Pyropia yezoensis and 11,667 orthologous gene families are specific to Z. marina. Furthermore, we identified the photoreceptors sensing red/far-red light and blue light. Also, we identified a large number of genes that are involved in ion transporters and channels including Na+ efflux, K+ uptake, Cl- channels, and H+ pumping.ConclusionsOur study contains an extensive sequencing and gene-annotation analysis of Z. marina. This information represents a genetic resource for the discovery of genes related to light sensing and salt tolerance in this species. Our transcriptome can be further utilized in future studies on molecular adaptation to abiotic stress in Z. marina.

Dataset Information

Comparative analysis of expressed sequence tag (EST) libraries in the seagrass Zostera marina subjected to temperature stress.

Publications

Comparative analysis of expressed sequence tag (EST) libraries in the seagrass Zostera marina subjected to temperature stress.

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