Number Of Novel Transcripts Research Articles

Gene Expression in the Developing Seed of Wild and Domesticated Rice.

The composition and nutritional properties of rice are the product of the expression of genes in the developing seed. RNA-Seq was used to investigate the level of gene expression at different stages of seed development in domesticated rice (Oryza sativa ssp. japonica var. Nipponbare) and two Australian wild taxa from the primary gene pool of rice (Oryza meridionalis and Oryza rufipogon type taxa). Transcriptome profiling of all coding sequences in the genome revealed that genes were significantly differentially expressed at different stages of seed development in both wild and domesticated rice. Differentially expressed genes were associated with metabolism, transcriptional regulation, nucleic acid processing, and signal transduction with the highest number of being linked to protein synthesis and starch/sucrose metabolism. The level of gene expression associated with domestication traits, starch and sucrose metabolism, and seed storage proteins were highest at the early stage (5 days post anthesis (DPA)) to the middle stage (15 DPA) and declined late in seed development in both wild and domesticated rice. However, in contrast, black hull colour (Bh4) gene was significantly expressed throughout seed development. A substantial number of novel transcripts (38) corresponding to domestication genes, starch and sucrose metabolism, and seed storage proteins were identified. The patterns of gene expression revealed in this study define the timing of metabolic processes associated with seed development and may be used to explain differences in rice grain quality and nutritional value.

PredLnc-GFStack: A Global Sequence Feature Based on a Stacked Ensemble Learning Method for Predicting lncRNAs from Transcripts.

Long non-coding RNAs (lncRNAs) are a class of RNAs with the length exceeding 200 base pairs (bps), which do not encode proteins, nevertheless, lncRNAs have many vital biological functions. A large number of novel transcripts were discovered as a result of the development of high-throughput sequencing technology. Under this circumstance, computational methods for lncRNA prediction are in great demand. In this paper, we consider global sequence features and propose a stacked ensemble learning-based method to predict lncRNAs from transcripts, abbreviated as PredLnc-GFStack. We extract the critical features from the candidate feature list using the genetic algorithm (GA) and then employ the stacked ensemble learning method to construct PredLnc-GFStack model. Computational experimental results show that PredLnc-GFStack outperforms several state-of-the-art methods for lncRNA prediction. Furthermore, PredLnc-GFStack demonstrates an outstanding ability for cross-species ncRNA prediction.

An efficient method for extracting next-generation sequencing quality RNA from liver tissue of recalcitrant animal species.

The next-generation RNA sequencing technologies expedite the discovery of a large number of novel transcripts and genes associated with various pathophysiological conditions. These technologies involve poly(A) enrichment, which in turn requires micrograms of high-quality total RNA. Unfortunately, the available RNA isolation approaches produce poor quality total RNA from difficult-to-isolate animal tissues, such as the liver with high glycogen content. Moreover, the extraction efficiencies of these approaches vary significantly depending on the animal species. To address this challenge, we optimized a three-step protocol for the extraction of high-yield and high-quality total RNA from the liver tissue (LT). The procedure effectively resolved the problem of glycogen coprecipitation by its stepwise removal. No signs of RNA degradation on gel electrophoresis analysis and RNA integrity number values ≥8.5 indicated that the extracted RNA is suitable for downstream processing, such as poly(A) enrichment and transcriptome profiling. To demonstrate the robustness of the novel protocol, a comparison was made with other currently available RNA extraction approaches from diverse resources. Whereas other protocols yielded partially degraded bands with either decreased or reversed ribosomal RNA (rRNA) ratio, our protocol yielded intact rRNA with a ratio of 2.0 ± 0.1. This optimized protocol was also successfully followed for other animal tissues, such as the bone and muscles. In conclusion, the study has described a highly efficient method for the next-generation sequencing quality RNA isolation from LT across a broad range of animal species, with extended applicability to other difficult-to-isolate tissues.

Transcriptome analysis of adult and fetal trabecular meshwork, cornea, and ciliary body tissues by RNA sequencing

PurposeTo characterize the transcriptional landscape of human adult and fetal trabecular meshwork (TM), cornea, and ciliary body (CB) tissues, and to evaluate the expression level of candidate genes selected from genetic association studies of primary-open angle glaucoma, central corneal thickness, intraocular pressure, vertical cup to disc ratio, and optic nerve parameters. MethodsDeep RNA sequencing was performed on the selected human tissues. Transcriptome analyses were performed to 1) characterize the total number of expressed genes, 2) identify the most highly expressed genes, 3) estimate the number of novel transcripts, and 4) evaluate the expression of candidate genes in each tissue. Finally, a differential gene expression analysis was conducted to compare the adult and fetal ocular tissues. ResultsThere was an average of 12,362 protein coding genes and 3725 novel transcripts expressed in each tissue. The top most expressed genes in each tissue included SPARC (fetal cornea and TM), APOD (adult TM), CLU (adult cornea), and PTGDS (adult and fetal CB). Twenty-nine candidate genes selected from genetic association studies primarily showed high expression levels in the trabecular meshwork and cornea. Comparison of adult and fetal samples identified 2012 and 1261 differentially expressed protein-coding genes within the cornea and trabecular meshwork, respectively. ConclusionsThis study has provided an unbiased glimpse into the transcriptome of three essential anterior ocular tissues, resulting in the development of several novel hypotheses. These data can be used in the future to better guide ocular research questions.

Genome-Wide Discovery of Tissue-Specific Genes in Maize

Analysis of spatial and temporal gene expression pattern is instrumental to elucidation of gene networks and molecular mechanisms of tissue development. It also holds great value to applied research by providing tissue-specific (TS) promoter candidates for transgenic studies. Here, we present a large-scale systematic discovery of tissue-specific genes in maize. Profiles of TS genes were generated from a maize transcriptome atlas, with 71, 539, 23, 352, 51, and 287 genes showing expression specificity in the root, leaf, cob, endosperm, silk, and anther. Functional annotations and enrichment analysis of these TS genes identified pathways overrepresented for each tissue. Tissue specificity was experimentally confirmed by RT-PCR, mRNA in situ hybridization, and transgenic expression of promoter-fluorescent proteins. Two significantly enriched binding motifs, CATTGYCG and KGGTATCA, were identified from the promoter analysis of the anther- and endosperm-specifically expressed genes. Further, co-expression analysis on a broader set of maize germplasms identified molecular networks of TS genes and revealed a number of novel transcripts including non-coding RNA expressing the same pattern with the TS genes from B73. Our global analysis of maize TS transcriptomes could shed light on the molecular mechanisms of tissue specificity and facilitate transgenic studies by providing a valuable resource of TS promoter candidates.

Transcriptome analysis of Rhizopus oryzae in response to xylose during fumaric acid production.

Xylose is one of the most abundant lignocellulosic components, but it cannot be used by R. oryzae for fumaric acid production. Here, we applied high-throughput RNA sequencing to generate two transcriptional maps of R. oryzae following fermentation in glucose or xylose. The differential expression analysis showed that, genes involved in amino acid metabolism, fatty acid metabolism, and gluconeogenesis, were up-regulated in response to xylose. Moreover, we discovered the potential presence of oxidative stress in R. oryzae during xylose fermentation. To adapt to this unfavorable condition, R. oryzae displayed reduced growth and induce of a number of antioxidant enzymes, including genes involved in glutathione, trehalose synthesis, and the proteasomal pathway. These responses might divert the flow of carbon required for the accumulation of fumaric acid. Furthermore, using high-throughput RNA sequencing, we identified a large number of novel transcripts and a substantial number of genes that underwent alternative splicing. Our analysis provides remarkable insight into the mechanisms underlying xylose fermentation by R. oryzae. These results may reveal potential target genes or strategies to improve xylose fermentation.

Small RNAs derived from tRNAs and rRNAs are highly enriched in exosomes from both old and new world Leishmania providing evidence for conserved exosomal RNA Packaging.

BackgroundLeishmania use exosomes to communicate with their mammalian hosts and these secreted vesicles appear to contribute to pathogenesis by delivering protein virulence factors to macrophages. In other eukaryotes, exosomes were found to carry RNA cargo, such as mRNAs and small non-coding RNAs, capable of altering recipient cell phenotype. Whether leishmania exosomes also contain RNAs which they are able to deliver to bystander cells is not known. Here, we show that leishmania exosomes indeed contain RNAs and compare and contrast the RNA content of exosomes released by Leishmania donovani and Leishmania braziliensis.ResultsWe purified RNA from exosomes collected from axenic amastigote culture supernatant and found that when compared with total leishmania RNA, exosomes mainly contained short RNA sequences. Exosomes with intact membranes were capable of protecting their RNA cargo from degradation by RNase. Moreover, exosome RNA cargo was delivered to host cell cytoplasm in vitro. Sequencing of exosomal RNA indicated that the majority of cargo sequences were derived from non-coding RNA species such as rRNA and tRNA. In depth analysis revealed the presence of tRNA-derived small RNAs, a novel RNA type with suspected regulatory functions. Northern blotting confirmed the specific and selective enrichment of tRNA-derived small RNAs in exosomes. We also identified a number of novel transcripts, which appeared to be specifically enriched in exosomes compared to total cell RNA. In addition, we observed the presence of sequences mapping to siRNA-coding regions in L. braziliensis , but not in L. donovani exosomes.ConclusionsThese results show that leishmania exosomes are selectively and specifically enriched in small RNAs derived almost exclusively from non-coding RNAs. These exosomes are competent to deliver their cargo of novel, potential small regulatory RNAs to macrophages where they may influence parasite-host cell interactions. The remarkably high degree of congruence in exosomal RNA content between L. donovani and L. braziliensis, argues for the presence of a conserved mechanism for exosomal RNA packaging in leishmania. These findings open up a new avenue of research on non-canonical, small RNA pathways in this trypanosomatid, which may elucidate pathogenesis and identify novel therapeutic approaches.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1260-7) contains supplementary material, which is available to authorized users.

Expression and characterization of digestive enzyme genes from hepatopancreatic transcripts from redclaw crayfish (Cherax quadricarinatus)

Redclaw crayfish, Cherax quadricarinatus, possess a number of biological and commercial attributes that make them ideal for commercial aquaculture. While some studies have investigated digestive enzyme activity and nutritional requirements of this species, little information exists about the expression of digestive enzyme genes and their role in regulating digestive capacity. The current study therefore sequenced and annotated a RNASeq library constructed from a redclaw hepatopancreas to identify genes involved in digestive enzyme production. We observed that most of the transcripts that were annotated as digestive enzyme genes are associated with carbohydrate metabolism, thus confirming that redclaw have an innate capacity to digest a range of carbohydrate substrates. While endoglucanases were the most abundant group of digestive enzymes found, a number of novel transcripts were also detected. Here, we provide the first report for the presence and expression of endo-b-mannanase in freshwater crayfish. This novel gene showed significant alignment with a GH5 family protein from marine Limnoriids, wood borers that do not possess symbiotic microbes in their gut system. Overall, the data generated here provide an important resource to better understand the suite of digestive enzymes in redclaw that are very useful to fully utilize the species’ digestive capacity and will assist development of specific artificial feeds.

Functional analysis of antisense long non-coding RNAs transcribed from the Bombyx mori (Lepidoptera: Bombycidae) nucleopolyhedrovirus genome

Although some viruses have been shown to encode long non-coding RNAs (lncRNAs), how they function during their infection cycles remains elusive. We previously found an unexpectedly large number of novel transcripts, including putative lncRNAs, which were expressed from the genome of the baculovirus Bombyx mori nucleopolyhedrovirus (BmNPV). To investigate the function of baculoviral antisense lncRNAs, we selected 15 BmNPV lncRNAs expressed from the baculovirus early or late promoter motif, and constructed the corresponding promoter knockout (PKO) viruses in which nucleotide substitutions were introduced at the transcription start sites of lncRNAs. We investigated the production of budded viruses (BVs) and occlusion bodies (OBs) in PKO virus-infected cultured cells and silkworm larvae. No defects in BV and OB production were observed for most of the PKO viruses, whereas KO122AS, in which an antisense lncRNA in the Bm122 locus was disrupted, produced fewer OBs than the wild-type or repair virus both in cultured cells and in silkworm larvae. Northern blot analysis revealed that loss of this antisense lncRNAs reduced the amounts of the corresponding sense mRNA. These results suggest that the lncRNA transcribed from the Bm122 locus might contribute to virus propagation by regulating viral gene expression. This is the first study to characterize the properties and functions of baculoviral lncRNAs.

Characterizing the Global Transcriptional Effects of TEL-AML1-Fusion in Childhood Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer affecting thousands of children worldwide each year. Most patients are cured but only after long chemotherapy treatment and still 15 % of them relapse. Therefore, better understanding of the molecular biology behind the disease is fundamental. TEL-AML1 fusion - comprised of two transcription factors important in hematopoiesis regulation - is the most frequent genetic variation found in 25 % of pediatric ALL-patients. The translocation occurs during pregnancy and is suggested to serve as a “first hit” enabling secondary changes that lead to cancer formation. Despite its frequency, genetic targets of this aberrant transcription factor are unclear, and its function in leukemia initiation and progression remains elusive.Here we aim at solving the genome-wide effects of TEL-AML1 on transcription using pre-B-leukemic cell models. After a time-series induction of wild-type or DNA-binding compromised mutated TEL-AML1, or a constitutive expression of shRNA silencing the fusion, the cells were studied using global nuclear run-on sequencing (GRO-seq). GRO-seq technology can map RNA polymerase II location and identify actively transcribed coding and non-coding genes and their directionality. Thus, GRO-seq provides a snapshot of global active transcription and was used here to identify bona fide targets of the TEL-AML1-fusion protein.In addition to transcriptional changes in known genes, we identified a notable number of novel transcripts including antisense-, lincRNA-, and microRNAs. We also characterized genomic locations where the fusion functions as a direct regulator by taking advantage of non-coding RNA transcripts known as enhancer RNAs. Furthermore, we performed transcription factor motif enrichment analysis on these active regulatory eRNA regions. The results uncover early transcriptional changes induced by TEL-AML1-fusion and may reveal critical steps in leukemia initiation and development. The findings also highlight the importance of non-coding RNAs in the pathogenesis of pediatric leukemia. DisclosuresNo relevant conflicts of interest to declare.

Analysis of the Drought Stress-Responsive Transcriptome of Black Cottonwood (Populus trichocarpa) Using Deep RNA Sequencing

The complete genome of Populus trichocarpa has been available for years, however, relatively little effort has been made to map and quantify the transcriptome for this important model organism. Here, we applied Illumina sequencing to systematically investigate the leaf transcriptomes derived from P. trichocarpa seedlings grown in normal condition and drought stress. On the basis of the available Populus genome, we defined gene structures and identified a number of novel transcripts and upstream open reading frames, which may be informative for understanding drought adaption of woody plants. We obtained 33,044 genes expressed in leaves covering ~80 % of the available P. trichocarpa gene models and 5689 genes were differentially expressed during drought stress. About 38.9 % of the expressed genes show alternative splicing (AS) patterns. Interestingly, the number of AS events and the expression of some AS genes increased when the plants were subjected to drought. At the physiological level, photosynthetic rates, stomatal conductance, and leaf water potential were significantly reduced after water stress. This was accompanied by strong transcriptional remodeling of energy metabolism, cell growth, carbohydrate metabolism, and cellular homeostasis in P. trichocarpa. In addition, genes involved in photosynthesis, cell wall organization, and osmoprotectants metabolism that may specially modulate the drought stress responses of P. trichocarpa are highlighted. Our analysis provides insight into the transcriptional responses of P. trichocarpa to drought stress and is expected to serve as valuable transcriptome resources for woody plants.

Development of endosperm transfer cells in barley.

Endosperm transfer cells (ETCs) are positioned at the intersection of maternal and filial tissues in seeds of cereals and represent a bottleneck for apoplasmic transport of assimilates into the endosperm. Endosperm cellularization starts at the maternal-filial boundary and generates the highly specialized ETCs. During differentiation barley ETCs develop characteristic flange-like wall ingrowths to facilitate effective nutrient transfer. A comprehensive morphological analysis depicted distinct developmental time points in establishment of transfer cell (TC) morphology and revealed intracellular changes possibly associated with cell wall metabolism. Embedded inside the grain, ETCs are barely accessible by manual preparation. To get tissue-specific information about ETC specification and differentiation, laser microdissection (LM)-based methods were used for transcript and metabolite profiling. Transcriptome analysis of ETCs at different developmental stages by microarrays indicated activated gene expression programs related to control of cell proliferation and cell shape, cell wall and carbohydrate metabolism reflecting the morphological changes during early ETC development. Transporter genes reveal distinct expression patterns suggesting a switch from active to passive modes of nutrient uptake with the onset of grain filling. Tissue-specific RNA-seq of the differentiating ETC region from the syncytial stage until functionality in nutrient transfer identified a high number of novel transcripts putatively involved in ETC differentiation. An essential role for two-component signaling (TCS) pathways in ETC development of barley emerged from this analysis. Correlative data provide evidence for abscisic acid and ethylene influences on ETC differentiation and hint at a crosstalk between hormone signal transduction and TCS phosphorelays. Collectively, the data expose a comprehensive view on ETC development, associated pathways and identified candidate genes for ETC specification.

Genome‐wide identification of novel small RNAs in Pseudomonas aeruginosa

Bacterial small regulatory RNAs (sRNAs) function in post-transcriptional control of gene expression and control a variety of processes including metabolic reactions, stress responses and pathogenesis in response to environmental signals. A variety of approaches have been used previously to identify 44 sRNAs in the opportunistic human pathogen Pseudomonas aeruginosa. In this work, RNA sequencing (RNA-seq) is used to identify novel transcripts in P.aeruginosa involving a combination of three different sequencing libraries. Almost all known sRNAs and over 500 novel intergenic sRNAs are identified with this approach. Although the use of three libraries increased the number of novel transcripts identified, there were significant differences in the subset of transcripts detected in each library, underscoring the importance of library preparation strategy and relative sRNA abundance for successful sRNA detection. Nearly 90% of the novel sRNAs have no orthologous bacterial sequences outside of P.aeruginosa, supporting a limited degree of sequence conservation and rapid evolution of sRNAs at the species level. We anticipate that the data will be useful for the study of regulatory sRNAs in bacteria and that the approach described here may be applied to identify sRNAs in any bacterium under different growth and stress conditions.

Identification and Characterization of Novel Genotoxic Stress-Inducible Nuclear Long Noncoding RNAs in Mammalian Cells

Whole transcriptome analyses have revealed a large number of novel transcripts including long and short noncoding RNAs (ncRNAs). Currently, there is great interest in characterizing the functions of the different classes of ncRNAs and their relevance to cellular processes. In particular, nuclear long ncRNAs may be involved in controlling various aspects of biological regulation, such as stress responses. By a combination of bioinformatic and experimental approaches, we identified 25 novel nuclear long ncRNAs from 6,088,565 full-length human cDNA sequences. Some nuclear long ncRNAs were conserved among vertebrates, whereas others were found only among primates. Expression profiling of the nuclear long ncRNAs in human tissues revealed that most were expressed ubiquitously. A subset of the identified nuclear long ncRNAs was induced by the genotoxic agents mitomycin C or doxorubicin, in HeLa Tet-off cells. There were no commonly altered nuclear long ncRNAs between mitomycin C- and doxorubicin-treated cells. These results suggest that distinct sets of nuclear long ncRNAs play roles in cellular defense mechanisms against specific genotoxic agents, and that particular long ncRNAs have the potential to be surrogate indicators of a specific cell stress.

Deep RNA sequencing improved the structural annotation of the Tuber melanosporum transcriptome

• The functional complexity of the Tuber melanosporum transcriptome has not yet been fully elucidated. Here, we applied high-throughput Illumina RNA-sequencing (RNA-Seq) to the transcriptome of T. melanosporum at different major developmental stages, that is free-living mycelium, fruiting body and ectomycorrhiza. • Sequencing of cDNA libraries generated a total of c. 24 million sequence reads representing > 882 Mb of sequence data. To construct a coverage signal profile across the genome, all reads were then aligned to the reference genome assembly of T. melanosporum Mel28. • We were able to identify a substantial number of novel transcripts, antisense transcripts, new exons, untranslated regions (UTRs), alternative upstream initiation codons and upstream open reading frames. • This RNA-Seq analysis allowed us to improve the genome annotation. It also provided us with a genome-wide view of the transcriptional and post-transcriptional mechanisms generating an increased number of transcript isoforms during major developmental transitions in T. melanosporum.

A spatial and temporal map of C. elegans gene expression.

The C. elegans genome has been completely sequenced, and the developmental anatomy of this model organism is described at single-cell resolution. Here we utilize strategies that exploit this precisely defined architecture to link gene expression to cell type. We obtained RNAs from specific cells and from each developmental stage using tissue-specific promoters to mark cells for isolation by FACS or for mRNA extraction by the mRNA-tagging method. We then generated gene expression profiles of more than 30 different cells and developmental stages using tiling arrays. Machine-learning-based analysis detected transcripts corresponding to established gene models and revealed novel transcriptionally active regions (TARs) in noncoding domains that comprise at least 10% of the total C. elegans genome. Our results show that about 75% of transcripts with detectable expression are differentially expressed among developmental stages and across cell types. Examination of known tissue- and cell-specific transcripts validates these data sets and suggests that newly identified TARs may exercise cell-specific functions. Additionally, we used self-organizing maps to define groups of coregulated transcripts and applied regulatory element analysis to identify known transcription factor- and miRNA-binding sites, as well as novel motifs that likely function to control subsets of these genes. By using cell-specific, whole-genome profiling strategies, we have detected a large number of novel transcripts and produced high-resolution gene expression maps that provide a basis for establishing the roles of individual genes in cellular differentiation.

P60. Functional analysis of stem cell-specific long non-coding RNAs in human embryonic carcinoma cell line NCCIT

Human stem cells are characterized by the ability for self-renewal and differentiation potential. These characteristics are likely governed by tight regulation of a molecular network that includes POU5F1, SOX2, and NANOG. In addition to known genes, transcriptome profiling studies have also identified a large number of novel transcripts that appear to be significantly expressed in stem cells. Several novel targets previously identified by reverseSAGE were investigated and these transcripts appear to be long non-coding RNAs. Two of these, HEST097 and HEST147, were further studied to determine possible connections to the stem cell fate. Real-time PCR showed specific expression of these targets in human embryonic stem cells (hESCs) and human embryonic carcinomas (hECCs), with little expression in other cell types, and was confirmed by SAGE database analysis. RNAi knockdown of HEST097 and HEST147 in hECC cell line NCCIT produced minor morphological changes and no overt signs of differentiation despite downregulation of NANOG. Cell proliferation appeared to be reduced and cell cycle markers were also affected. Intriguingly, siRNA knockdown of HEST147 resulted in downregulation of FGF4 expression, a gene that is located on the chromosome region downstream to HEST147. This may possibly point towards a role in which the stability of a long non-coding RNA may affect expression of a neighbouring transcript on its chromosome location. The discovery of these stem cell-specific transcripts raises interesting questions where further studies would be required in order to determine the possible mechanisms in which long non-coding RNAs may affect the stem cell fate.

Mass identification of transcriptional units expressed from the Bombyx mori nucleopolyhedrovirus genome

In order to identify the transcriptional units expressed from an entire nucleopolyhedrovirus (NPV) genome during infection, we constructed a full-length-enriched cDNA library from Bombyx mori NPV (BmNPV)-infected BmN cells. We randomly sequenced 11,520 clones from both ends to obtain a total of 4679 BmNPV-derived transcriptional units. The data revealed a number of novel transcripts, including putative non-coding RNAs, most of which are expressed from recognized baculovirus early or late promoter motifs. These findings provide new insights into the complex transcriptional regulation of an NPV genome and suggest roles for as-yet-uncharacterized transcripts.

Survey of the transcriptome of Aspergillus oryzae via massively parallel mRNA sequencing

Aspergillus oryzae, an important filamentous fungus used in food fermentation and the enzyme industry, has been shown through genome sequencing and various other tools to have prominent features in its genomic composition. However, the functional complexity of the A. oryzae transcriptome has not yet been fully elucidated. Here, we applied direct high-throughput paired-end RNA-sequencing (RNA-Seq) to the transcriptome of A. oryzae under four different culture conditions. With the high resolution and sensitivity afforded by RNA-Seq, we were able to identify a substantial number of novel transcripts, new exons, untranslated regions, alternative upstream initiation codons and upstream open reading frames, which provide remarkable insight into the A. oryzae transcriptome. We were also able to assess the alternative mRNA isoforms in A. oryzae and found a large number of genes undergoing alternative splicing. Many genes and pathways that might be involved in higher levels of protein production in solid-state culture than in liquid culture were identified by comparing gene expression levels between different cultures. Our analysis indicated that the transcriptome of A. oryzae is much more complex than previously anticipated, and these results may provide a blueprint for further study of the A. oryzae transcriptome.

Deep RNA sequencing at single base-pair resolution reveals high complexity of the rice transcriptome

Understanding the dynamics of eukaryotic transcriptome is essential for studying the complexity of transcriptional regulation and its impact on phenotype. However, comprehensive studies of transcriptomes at single base resolution are rare, even for modern organisms, and lacking for rice. Here, we present the first transcriptome atlas for eight organs of cultivated rice. Using high-throughput paired-end RNA-seq, we unambiguously detected transcripts expressing at an extremely low level, as well as a substantial number of novel transcripts, exons, and untranslated regions. An analysis of alternative splicing in the rice transcriptome revealed that alternative cis-splicing occurred in approximately 33% of all rice genes. This is far more than previously reported. In addition, we also identified 234 putative chimeric transcripts that seem to be produced by trans-splicing, indicating that transcript fusion events are more common than expected. In-depth analysis revealed a multitude of fusion transcripts that might be by-products of alternative splicing. Validation and chimeric transcript structural analysis provided evidence that some of these transcripts are likely to be functional in the cell. Taken together, our data provide extensive evidence that transcriptional regulation in rice is vastly more complex than previously believed.