Project description:Tremella fuciformis is a popular edible fungus with fruiting bodies that can be produced in large quantities at low costs, while it is easy to transform and cultivate as yeast. This makes it an attractive potential bioreactor. Enhanced heterologous gene expression through codon optimization would be useful, but until now codon usage preferences in T. fuciformis remain unknown. The only available genome of a species in the genus Tremella was that of Tremella mesenterica. To precisely determine the preferred codon usage of T. fuciformis we sequenced the genome of strain Tr26 resulting in a 24.5 Mb draft genome with 10,040 predicted genes. 3288 of the derived predicted proteins matched the UniProtKB/Swiss-Prot databases with 40% or more similarity. Corresponding gene models of this subset were subsequently optimized trough repetitive comparison of alternative start codons and selection of best length matching gene models. For experimental confirmation of gene models, 96 random clones from an existing T. fuciformis cDNA library were sequenced, generating 80 complete CDSs. Calculated optimal codons (RSCU and RFCU values) for the 3288 predicted and the 80 cloned CDSs were highly similar, indicating sufficient accuracy of predicted gene models for codon usage analysis. T. fuciformis showed a strong preference for C and then G (C+G; 66.4 %) at the third base pair position of used codons, while average GC content of predicted genes was slightly higher (58.5 %) than he total genome sequence average (55.9%). Most frequently used codons (optimal codons) all ended in C or G except for one (Ter; AGU), and an increased frequency of C ending codons was observed in genes with higher expression levels. Surprisingly, the preferred codon usage in T. fuciformis strongly differed from T. mesenterica (same genus) and C. neoformans (same family). Instead, optimal codon usage was similar to more distant related species such as Ustilago maydis and Neurospora crassa. Despite much higher overall sequence homology between T. fuciformis and T. mesenterica only 7 out of 21 optimal codons were equal, whereas T. fuciformis shared up to 20 out 21 optimal codons with other species. Clearly, codon usage in Tremella can differ largely and should be estimated for individual species. The precise identification of optimal and high expression related codons is therefore an important step in the development of T. fuciformis as a bioreactor system. Using the Total RNA was extracted from yeast-like cells of T. fuciformis Tr21 in their exponential growth stage, and double-stranded cDNA was synthesized for tag library construction and digital gene expression tag (DGE) sequencing at BGI Tech Solutions Co., Ltd (Shenzhen, China). Image analysis, base calling, extraction of tags, and tag counting were conducted using the Illumina pipeline. Clean tags were mapped to predicted gene models of the draft genome with a mismatch tolerance of 1bp. The number of tags for each CDS was calculated and then normalized to TPM (number of transcripts per million clean tags) digital gene expression (DGE)

Project description:Tremella fuciformis is a popular edible fungus with fruiting bodies that can be produced in large quantities at low costs, while it is easy to transform and cultivate as yeast. This makes it an attractive potential bioreactor. Enhanced heterologous gene expression through codon optimization would be useful, but until now codon usage preferences in T. fuciformis remain unknown. The only available genome of a species in the genus Tremella was that of Tremella mesenterica. To precisely determine the preferred codon usage of T. fuciformis we sequenced the genome of strain Tr26 resulting in a 24.5 Mb draft genome with 10,040 predicted genes. 3288 of the derived predicted proteins matched the UniProtKB/Swiss-Prot databases with 40% or more similarity. Corresponding gene models of this subset were subsequently optimized trough repetitive comparison of alternative start codons and selection of best length matching gene models. For experimental confirmation of gene models, 96 random clones from an existing T. fuciformis cDNA library were sequenced, generating 80 complete CDSs. Calculated optimal codons (RSCU and RFCU values) for the 3288 predicted and the 80 cloned CDSs were highly similar, indicating sufficient accuracy of predicted gene models for codon usage analysis. T. fuciformis showed a strong preference for C and then G (C+G; 66.4 %) at the third base pair position of used codons, while average GC content of predicted genes was slightly higher (58.5 %) than he total genome sequence average (55.9%). Most frequently used codons (optimal codons) all ended in C or G except for one (Ter; AGU), and an increased frequency of C ending codons was observed in genes with higher expression levels. Surprisingly, the preferred codon usage in T. fuciformis strongly differed from T. mesenterica (same genus) and C. neoformans (same family). Instead, optimal codon usage was similar to more distant related species such as Ustilago maydis and Neurospora crassa. Despite much higher overall sequence homology between T. fuciformis and T. mesenterica only 7 out of 21 optimal codons were equal, whereas T. fuciformis shared up to 20 out 21 optimal codons with other species. Clearly, codon usage in Tremella can differ largely and should be estimated for individual species. The precise identification of optimal and high expression related codons is therefore an important step in the development of T. fuciformis as a bioreactor system.

Project description:Genes that are constitutively expressed across multiple environmental stimuli are crucial to quantifying differentially expressed genes, particularly when employing quantitative reverse transcriptase polymerase chain reaction (RT-qPCR) assays. However, the identification of these potential reference genes in non-model organisms is challenging and is often guided by expression patterns in distantly related organisms. Here, transcriptome datasets from the diatom Thalassiosira pseudonana grown under replete, phosphorus-limited, iron-limited, and phosphorus and iron co-limited nutrient regimes were analyzed through literature-based searches for homologous reference genes, k-means clustering, and Analysis of Sequence Counts (ASC) to identify putative reference genes. A total of 9759 genes were identified and screened for stable expression. Literature-based searches surveyed 18 generally accepted reference genes, revealing 101 homologs in T. pseudonana with variable expression and a wide range of mean tags per million. K-means analysis parsed the whole transcriptome into 15 clusters. The two most stable clusters contained 709 genes but still had distinct patterns in expression. ASC analyses identified 179 genes that were stably expressed (posterior probability < 0.1 for 1.25 fold change). Genes known to have a stable expression pattern across the test treatments, like actin, were identified in this pool of 179 candidate genes. ASC can be employed on data without biological replicates and was more robust than the k-means approach in isolating genes with stable expression. The intersection of the genes identified through ASC with commonly used reference genes from the literature suggests that actin and ubiquitin ligase may be useful reference genes for T. pseudonana and potentially other diatoms. With the wealth of transcriptome sequence data becoming available, ASC can be easily applied to transcriptome datasets from other phytoplankton to identify reference genes. Axenic T. pseudonana CCMP 1335 was grown at 14Â°C under 24 hour light (120 Âµmol photons m-2 s-1) after Dyhrman et al. (2012) in f/2 plus silica chelated media made from surface Sargasso Sea water. Nitrate, silica, vitamins, and trace metals were at f/2 concentrations (Guillard and Ryther 1962), while iron and phosphate were modified across treatments. In brief, triplicate cultures of replete (36 ÂµM PO4, 400 nM Fe), P-limited (0.4 ÂµM PO4, 400 nM Fe), Fe-limited (36 ÂµM PO4, 40 nM Fe), and Co-limited (0.4 ÂµM PO4, 40 nM Fe) treatments were harvested when growth deviated from the replete control. Growth was monitored by cell counts. Biomass was harvested onto 0.2 Âµm filters and flash frozen in liquid nitrogen and total RNA was extracted as described in Dyhrman et al. (2012). Tag-seq sequencing of the transcriptome was performed by Illumina with a polyA selection and NlaIII digestion, resulting in 21 bp sequence reads or tags (Dyhrman et al., 2012). Libraries were of varied sizes as follows: replete (~12 million), P-limited (~13 million), Fe-limited (~23 million), and Co-limited (~26 million). Tags were mapped to gene models (predicted protein coding regions) with a pipeline designed by Genesifter Inc., requiring 100% identity and covering 9759 genes. Tag counts within a gene were pooled and normalized to the size of the library, with resulting data expressed in tags per million (tpm). Genes with normalized tag counts less than 2.5 tpm for each of the four treatments were excluded (Figure S1) , leaving 7380 genes in the analysis.

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Blue light exposure and nutrient conditions influence the expression of genes involved in simultaneous hyphal knot formation in Coprinopsis cinerea.

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