C4 leaf development and evolution.

C4 photosynthesis is more efficient than C3 photosynthesis for two reasons. First, C4 plants have evolved efficient C4 enzymes to suppress wasteful photorespiration and enhance CO2 fixation. Second, C4 leaves have Kranz anatomy in which the veins are surrounded by one layer of bundle sheath (BS) cells and one layer of mesophyll (M) cells. The BS and M cells are functionally well differentiated and also well coordinated for rapid assimilation of atmospheric CO2 and transport of photo-assimilates between the two types of cells. Recent comparative transcriptomics of developing M and BS cells in young maize embryonic leaves revealed not only potential regulators of BS and M cell differentiation but also rapid early BS cell differentiation whereas slower, more prolonged M cell differentiation, contrary to the traditional view of a far simpler process of M cell development. Moreover, new upstream regulators of Kranz anatomy development have been identified and a number of gene co-expression modules for early vascular development have been inferred. Also, a candidate gene regulatory network associated with Kranz anatomy and vascular development has been constructed. Additionally, how whole genome duplication (WGD) may facilitate C4 evolution has been studied and the reasons for why the same WGD event led to successful C4 evolution in Gynandropsis gynandra but not in the sister species Tarenaya hassleriana have been proposed. Finally, new future research directions are suggested.

Regulators of early maize leaf development inferred from transcriptomes of laser capture microdissection (LCM)-isolated embryonic leaf cells.

The superior photosynthetic efficiency of C4 leaves over C3 leaves is owing to their unique Kranz anatomy, in which the vein is surrounded by one layer of bundle sheath (BS) cells and one layer of mesophyll (M) cells. Kranz anatomy development starts from three contiguous ground meristem (GM) cells, but its regulators and underlying molecular mechanism are largely unknown. To identify the regulators, we obtained the transcriptomes of 11 maize embryonic leaf cell types from five stages of pre-Kranz cells starting from median GM cells and six stages of pre-M cells starting from undifferentiated cells. Principal component and clustering analyses of transcriptomic data revealed rapid pre-Kranz cell differentiation in the first two stages but slow differentiation in the last three stages, suggesting early Kranz cell fate determination. In contrast, pre-M cells exhibit a more prolonged transcriptional differentiation process. Differential gene expression and coexpression analyses identified gene coexpression modules, one of which included 3 auxin transporter and 18 transcription factor (TF) genes, including known regulators of Kranz anatomy and/or vascular development. In situ hybridization of 11 TF genes validated their expression in early Kranz development. We determined the binding motifs of 15 TFs, predicted TF target gene relationships among the 18 TF and 3 auxin transporter genes, and validated 67 predictions by electrophoresis mobility shift assay. From these data, we constructed a gene regulatory network for Kranz development. Our study sheds light on the regulation of early maize leaf development and provides candidate leaf development regulators for future study.

Histone H3K27 demethylase UTX compromises articular chondrocyte anabolism and aggravates osteoarthritic degeneration.

Epigenome alteration in chondrocytes correlates with osteoarthritis (OA) development. H3K27me3 demethylase UTX regulates tissue homeostasis and deterioration, while its role was not yet studied in articulating joint tissue in situ. We now uncovered that increased UTX and H3K27me3 expression in articular chondrocytes positively correlated with human knee OA. Forced UTX expression upregulated the H3K27me3 enrichment at transcription factor Sox9 promoter, inhibiting key extracellular matrix molecules collagen II, aggrecan, and glycosaminoglycan in articular chondrocytes. Utx overexpression in knee joints aggravated the signs of OA, including articular cartilage damage, synovitis, osteophyte formation, and subchondral bone loss in mice. Chondrocyte-specific Utx knockout mice developed thicker articular cartilage than wild-type mice and showed few gonarthrotic symptoms during destabilized medial meniscus- and collagenase-induced joint injury. In vitro, Utx loss changed H3K27me3-binding epigenomic landscapes, which contributed to mitochondrial activity, cellular senescence, and cartilage development. Insulin-like growth factor 2 (Igf2) and polycomb repressive complex 2 (PRC2) core components Eed and Suz12 were, among others, functional target genes of Utx. Specifically, Utx deletion promoted Tfam transcription, mitochondrial respiration, ATP production and Igf2 transcription but inhibited Eed and Suz12 expression. Igf2 blockade or forced Eed or Suz12 expression increased H3K27 trimethylation and H3K27me3 enrichment at Sox9 promoter, compromising Utx loss-induced extracellular matrix overproduction. Taken together, UTX repressed articular chondrocytic activity, accelerating cartilage loss during OA. Utx loss promoted cartilage integrity through epigenetic stimulation of mitochondrial biogenesis and Igf2 transcription. This study highlighted a novel noncanonical role of Utx, in concert with PRC2 core components, in controlling H3K27 trimethylation and articular chondrocyte anabolism and OA development.

Single-cell transcriptomics reveals a low CD8+ T cell infiltrating state mediated by fibroblasts in recurrent renal cell carcinoma.

PURPOSE: Recurrent renal cell carcinoma(reRCC) is associated with poor prognosis and the underlying mechanism is not yet clear. A comprehensive understanding of tumor microenvironment (TME) of reRCC may aid in designing effective anticancer therapies, including immunotherapies. Single-cell transcriptomics holds great promise for investigating the TME, however, this technique has not been used in reRCC. Here, we aimed to explore the difference in the TME and gene expression pattern between primary RCC (pRCC) and reRCC at single-cell level. EXPERIMENTAL DESIGN: We performed single-cell RNA sequencing analyses of 32,073 cells from 2 pRCC, 2 reRCC, and 3 adjacent normal kidney samples. 41 pairs of pRCC and reRCC samples were collected as a validation cohort to assess differences observed in single-cell sequencing. The prognostic significance of related cells and markers were studied in 47 RCC patients underwent immunotherapy. The function of related cells and markers were validated via in vitro and in vivo experiments. RESULTS: reRCC had reduced CD8+ T cells but increased cancer-associated fibroblasts (CAFs) infiltration compared with pRCC. Reduced CD8+ T cells and increased CAFs infiltration were significantly associated with a worse response from immunotherapy. Remarkably, CAFs showed substantial expression of LGALS1 (Gal1). In vitro, CAFs could induce CD8+ T cells apoptosis via Gal1. In vivo, knockdown of Gal1 in CAFs suppressed tumor growth, increased CD8+ T cells infiltration, reduced the proportion of apoptotic CD8+ T cells and enhanced the efficacy of immunotherapy. CONCLUSIONS: We delineated the heterogeneity of reRCC and highlighted an innovative mechanism that CAFs acted as a suppressor of CD8+ T cells via Gal1. Targeting Gal1 combined with anti-PD1 showed promising efficacy in treating RCC.

LRPPRC regulates redox homeostasis via the circANKHD1/FOXM1 axis to enhance bladder urothelial carcinoma tumorigenesis.

Reactive oxygen species (ROS) which are continuously generated mainly by mitochondria, have been proved to play an important role in the stress signaling of cancer cells. Moreover, pentatricopeptide repeat (PPR) proteins have been suggested to take part in mitochondrial metabolism. However, the mechanisms integrating the actions of these distinct networks in urothelial carcinoma of the bladder (UCB) pathogenesis are elusive. In this study, we found that leucine rich pentatricopeptide repeat containing (LRPPRC) was frequently upregulated in UCB and that it was an independent prognostic factor in UCB. We further revealed that LRPPRC promoted UCB tumorigenesis by regulating the intracellular ROS homeostasis. Mechanistically, LRPPRC modulates ROS balance and protects UCB cells from oxidative stress via mt-mRNA metabolism and the circANKHD1/FOXM1 axis. In addition, the SRA stem-loop interacting RNA binding protein (SLIRP) directly interacted with LRPPRC to protect it from ubiquitination and proteasomal degradation. Notably, we showed that LRPPRC modulated the tumorigenesis of UCB cells in a circANKHD1-FOXM1-dependent manner. In conclusion, LRPPRC exerts critical roles in regulating UCB redox homeostasis and tumorigenesis, and is a prognostic factor for UCB; suggesting that LRPPRC may serve as an exploitable therapeutic target in UCB.

Ureteral stents cannot decrease the incidence of ureteroileal anastomotic stricture and leakage: A systematic review and meta-analysis.

BACKGROUND: The ileal conduit and ileal orthotopic neobladder were the most popular methods for urinary diversion following radical cystectomy. Stenting the anastomosis of ileo-ureter or ureter-neobladder was a common practice. However, it is still controversial if ureteral stents could prevent complications such as ureteroileal anastomosis stricture (UIAS) and ureteroileal anastomosis leakage (UIAL) after ureteral anastomosis. OBJECTIVES: This study aims to investigate the role of the ureteral stent in preventing UIAS and UIAL. DATA SOURCES: We systematically searched the related studies in PubMed, Embase, and Cochrane Library up to June 2020. STUDY ELIGIBILITY CRITERIA: Cohort studies that identified the use of stent and the incidence of UIAS or UIAL were recorded. DATA SYNTHESIS: Comparative meta-analysis was conducted on four cohort studies for comparison of UIAS and UIAL between the stented and nonstented groups. Besides, eleven studies which reported the events of UIAS and UIAL were used for meta-analysis of single proportion. RESULTS: A total of 11 studies were qualified for analysis. Comparative meta-analysis identified that the incidence of UIAS was higher in the stented group than that in the nonstented group, but this did not reach a significant difference (odds ratio [OR]: 1.64; 95% confidence interval [CI]: 0.88-3.05; P = 0.12). Besides, there was no difference in the incidences of UIAL between the stented and the nonstented groups. On meta-analysis of single proportion, the incidence of UIAS was 7% (95% CI: 3%-10%) in the stented group and 3% (95% CI: 1%-6%) in the nonstented group. The UIAL rate was 1% (95% CI, 0%-4%) in stented patients and 2% (95% CI, 1%-4%) in nonstented patients. CONCLUSION: Stenting the ureteroileal anastomosis resulted in a higher incidence of UIAS. There is no evidence to support ureteral stents could prevent the occurrence of UIAL after urinary diversion.

Discovering unknown human and mouse transcription factor binding sites and their characteristics from ChIP-seq data.

Transcription factor binding sites (TFBSs) are essential for gene regulation, but the number of known TFBSs remains limited. We aimed to discover and characterize unknown TFBSs by developing a computational pipeline for analyzing ChIP-seq (chromatin immunoprecipitation followed by sequencing) data. Applying it to the latest ENCODE ChIP-seq data for human and mouse, we found that using the irreproducible discovery rate as a quality-control criterion resulted in many experiments being unnecessarily discarded. By contrast, the number of motif occurrences in ChIP-seq peak regions provides a highly effective criterion, which is reliable even if supported by only one experimental replicate. In total, we obtained 2,058 motifs from 1,089 experiments for 354 human TFs and 163 motifs from 101 experiments for 34 mouse TFs. Among these motifs, 487 have not previously been reported. Mapping the canonical motifs to the human genome reveals a high TFBS density ±2 kb around transcription start sites (TSSs) with a peak at -50 bp. On average, a promoter contains 5.7 TFBSs. However, 70% of TFBSs are in introns (41%) and intergenic regions (29%), whereas only 12% are in promoters (-1 kb to +100 bp from TSSs). Notably, some TFs (e.g., CTCF, JUN, JUNB, and NFE2) have motifs enriched in intergenic regions, including enhancers. We inferred 142 cobinding TF pairs and 186 (including 115 completely) tethered binding TF pairs, indicating frequent interactions between TFs and a higher frequency of tethered binding than cobinding. This study provides a large number of previously undocumented motifs and insights into the biological and genomic features of TFBSs.

Rice transcription factor GAMYB modulates bHLH142 and is homeostatically regulated by TDR during anther tapetal and pollen development.

GIBBERELLIN MYB GENE (GAMYB), UNDEVELOPED TAPETUM1 (UDT1), TDR INTERACTING PROTEIN2 (TIP2/bHLH142), TAPETUM DEGENERATION RETARDATION (TDR), and ETERNAL TAPETUM 1/DELAYED TAPETUM DEGENERATION (EAT1/DTD) are important transcription factors that play a crucial role during pollen development in rice. This study demonstrates that bHLH142 acts downstream of UDT1 and GAMYB and works as a 'hub' in these two pollen pathways. We show that GAMYB modulates bHLH142 expression through specific binding to the MYB motif of the bHLH142 promoter during the early stage of pollen development, while TDR acts as a transcriptional repressor of the GAMYB modulation of bHLH142 by binding to the E-box close to the MYB motif on the promoter. Altered expression of these transcription factors highlights that a tight, precise, and coordinated regulation among them is essential for normal pollen development. Most notably, we show that the regulatory pathways of GAMYB and UDT1 rely on bHLH142 in a direct and indirect manner, respectively, and function in different tissues with distinct biological roles during pollen development. This study advances our understanding of the molecular mechanisms of rice pollen development.

Prognostic significance of tumor-infiltrating immune cells in muscle-invasive bladder cancer.

BACKGROUND: Muscle-invasive bladder cancer (MIBC) is a lethal disease with poor treatment response and a high death rate. Immune cells infiltrating the tumor tissues have been shown to play a vital role in tumorigenesis and tumor progression, but their prognostic significance in MIBC remains unclear. OBJECTIVES: To explore the landscape and prognostic significance of tumor-infiltrating immune cells (TIICs) in MIBC, and to develop a model to improve the prognostic predictions of MIBC. METHODS AND MATERIALS: The gene expression profile and clinical data of MIBC patients were downloaded from the Gene Expression Omnibus and The Cancer Genome Atlas portal. The fractions of 22 TIIC subtypes were calculated using the Cell Type Identification by Estimating Relative Subsets of RNA Transcripts (CIBERSORT) algorithm. A TIICs-based model was constructed using least absolute shrinkage and selection operator (LASSO) Cox regression in a training cohort and validated in the validation cohort. RESULTS: Ten types of TIICs demonstrated different infiltration abundance between MIBC and normal tissue. We also found 11 types of TIICs that were significantly associated with overall survival (OS). A TIICs-based model was established, consisting of 15 types of immune cells, and an immunoscore was calculated. Significant differences in OS were found between the high and low immunoscore groups, in both training (n = 343) and validation (n = 146) cohorts. The model could identify patients who would have worse OS despite having similar clinical characteristics. Furthermore, multivariate analysis identified the immunoscore as an independent risk factor (hazard ratio, 3.23; 95% confidence interval; 2.22-4.70) for OS in MIBC patients. CONCLUSION: The landscape of immune infiltration is different between MIBC and normal tissue. The TIICs-based model could provide promising predictive value to complement the existing staging system for predicting the OS of MIBC patients.

Maize ANT1 modulates vascular development, chloroplast development, photosynthesis, and plant growth.

Arabidopsis AINTEGUMENTA (ANT), an AP2 transcription factor, is known to control plant growth and floral organogenesis. In this study, our transcriptome analysis and in situ hybridization assays of maize embryonic leaves suggested that maize ANT1 (ZmANT1) regulates vascular development. To better understand ANT1 functions, we determined the binding motif of ZmANT1 and then showed that ZmANT1 binds the promoters of millet SCR1, GNC, and AN3, which are key regulators of Kranz anatomy, chloroplast development, and plant growth, respectively. We generated a mutant with a single-codon deletion and two frameshift mutants of the ANT1 ortholog in the C4 millet Setaria viridis by the CRISPR/Cas9 technique. The two frameshift mutants displayed reduced photosynthesis efficiency and growth rate, smaller leaves, and lower grain yields than wild-type (WT) plants. Moreover, their leaves sporadically exhibited distorted Kranz anatomy and vein spacing. Conducting transcriptomic analysis of developing leaves in the WT and the three mutants we identified differentially expressed genes (DEGs) in the two frameshift mutant lines and found many down-regulated DEGs enriched in photosynthesis, heme, tetrapyrrole binding, and antioxidant activity. In addition, we predicted many target genes of ZmANT1 and chose 13 of them to confirm binding of ZmANT1 to their promoters. Based on the above observations, we proposed a model for ANT1 regulation of cell proliferation and leaf growth, vascular and vein development, chloroplast development, and photosynthesis through its target genes. Our study revealed biological roles of ANT1 in several developmental processes beyond its known roles in plant growth and floral organogenesis.

Mutational signatures and mutagenic impacts associated with betel quid chewing in oral squamous cell carcinoma.

Betel quid (BQ) chewing is a prevailing risk for oral squamous cell carcinoma (OSCC) in Southeast Asia. Yet, the detailed mechanisms by which BQ chewing damages the genome are still not fully understood. Through exome sequencing of tumor-normal pairs from 196 male patients with OSCC, including 95 habitual BQ chewers and 101 non-BQ users, we conducted a quantitative survey of mutational signatures and genomic aberrations and explored their association with BQ chewing. We found that BQ-associated elevation in mutation rate was seen in cancers of the tongue, but not in overall OSCC. Additionally, we identified a mutational signature that is enriched in tumors from BQ users. Moreover, the numbers of small insertions and deletions (INDELs) and breakpoints derived from structural variations (SV) were increased, whereas the extent of loss of heterozygosity was decreased in BQ-related OSCC genomes. However, neither the number of base substitutions and microsatellite instability events nor the extent of copy-number alterations differed between BQ-related and -unrelated OSCC. In conclusion, consistent with the proposition that BQ chewing increases OSCC risk as a mutagen, our results unveil a BQ-associated mutational signature and indicate mutagenic impacts of BQ chewing on preferentially eliciting INDELs and SV-related breakpoints in OSCC genomes.

Many human RNA viruses show extraordinarily stringent selective constraints on protein evolution.

How negative selection, positive selection, and population size contribute to the large variation in nucleotide substitution rates among RNA viruses remains unclear. Here, we studied the ratios of nonsynonymous-to-synonymous substitution rates (dN/dS) in protein-coding genes of human RNA and DNA viruses and mammals. Among the 21 RNA viruses studied, 18 showed a genome-average dN/dS from 0.01 to 0.10, indicating that over 90% of nonsynonymous mutations are eliminated by negative selection. Only HIV-1 showed a dN/dS (0.31) higher than that (0.22) in mammalian genes. By comparing the dN/dS values among genes in the same genome and among species or strains, we found that both positive selection and population size play significant roles in the dN/dS variation among genes and species. Indeed, even in flaviviruses and picornaviruses, which showed the lowest ratios among the 21 species studied, positive selection appears to have contributed significantly to dN/dS We found the view that positive selection occurs much more frequently in influenza A subtype H3N2 than subtype H1N1 holds only for the hemagglutinin and neuraminidase genes, but not for other genes. Moreover, we found no support for the view that vector-borne RNA viruses have lower dN/dS ratios than non-vector-borne viruses. In addition, we found a correlation between dN and dS, implying a correlation between dN and the mutation rate. Interestingly, only 2 of the 8 DNA viruses studied showed a dN/dS < 0.10, while 4 showed a dN/dS > 0.22. These observations increase our understanding of the mechanisms of RNA virus evolution.

Comparative transcriptomics method to infer gene coexpression networks and its applications to maize and rice leaf transcriptomes.

Time-series transcriptomes of a biological process obtained under different conditions are useful for identifying the regulators of the process and their regulatory networks. However, such data are 3D (gene expression, time, and condition), and there is currently no method that can deal with their full complexity. Here, we developed a method that avoids time-point alignment and normalization between conditions. We applied it to analyze time-series transcriptomes of developing maize leaves under light-dark cycles and under total darkness and obtained eight time-ordered gene coexpression networks (TO-GCNs), which can be used to predict upstream regulators of any genes in the GCNs. One of the eight TO-GCNs is light-independent and likely includes all genes involved in the development of Kranz anatomy, which is a structure crucial for the high efficiency of photosynthesis in C4 plants. Using this TO-GCN, we predicted and experimentally validated a regulatory cascade upstream of SHORTROOT1, a key Kranz anatomy regulator. Moreover, we applied the method to compare transcriptomes from maize and rice leaf segments and identified regulators of maize C4 enzyme genes and RUBISCO SMALL SUBUNIT2 Our study provides not only a powerful method but also novel insights into the regulatory networks underlying Kranz anatomy development and C4 photosynthesis.

Popmarker: Identifying Phylogenetic Markers at the Population Level.

As phylogenomic approach becomes a common practice for constructing true bacterial phylogenies, it has become apparent that single molecular markers such as 16S ribosomal DNA often lead to misclassification of species. In this study, we present a program called Popmarker that uses the true species phylogeny and identifies a minimum set of molecular markers reflecting the bacterial evolution history and phylogenetic relationship at the resolution of populations. Popmarker ranks the proteome according to the correlation of whole species tree or subtree branch length against orthologous sequence distances. We demonstrate that 5 proteins of 2 top ranks achieve the same resolution as concatenation of 2203 single-copy orthologous genes and the right species classification as well as correct split of the 2 groups of Vibrio campbellii . The top-ranking genes selected by Popmarker are candidates that lead to speciation and are useful in distinguishing close related species in microbiome study.

Elevated auxin biosynthesis and transport underlie high vein density in C4 leaves.

High vein density, a distinctive trait of C4 leaves, is central to both C3-to-C4 evolution and conversion of C3 to C4-like crops. We tested the hypothesis that high vein density in C4 leaves is due to elevated auxin biosynthesis and transport in developing leaves. Up-regulation of genes in auxin biosynthesis pathways and higher auxin content were found in developing C4 leaves compared with developing C3 leaves. The same observation held for maize foliar (C4) and husk (C3) leaf primordia. Moreover, auxin content and vein density were increased in loss-of-function mutants of Arabidopsis MYC2, a suppressor of auxin biosynthesis. Treatment with an auxin biosynthesis inhibitor or an auxin transport inhibitor led to much fewer veins in new leaves. Finally, both Arabidopsis thaliana auxin efflux transporter pin1 and influx transporter lax2 mutants showed reduced vein numbers. Thus, development of high leaf vein density requires elevated auxin biosynthesis and transport.

Predicting Transcription Factor Binding Sites and Their Cognate Transcription Factors Using Gene Expression Data.

A transcription factor (TF) is a DNA binding protein that targets specific binding-sites (TFBSs) to regulate the transcript levels of its downstream genes. Thus, identifying the TF-TFBS pairs is a pivotal step in understanding the function of TFs and the regulatory network in an organism. Here, we describe two methods for predicting the TFBS of a given TF and for predicting the cognate TF of a given TFBS from a set of strongly co-expressed genes, using time-course transcriptome data of maize developing leaves.

Exome Sequencing of Oral Squamous Cell Carcinoma Reveals Molecular Subgroups and Novel Therapeutic Opportunities.

Oral squamous cell carcinoma (OSCC), an epithelial malignancy affecting a variety of subsites in the oral cavity, is prevalent in Asia. The survival rate of OSCC patients has not improved over the past decades due to its heterogeneous etiology, genetic aberrations, and treatment outcomes. Improvement in therapeutic strategies and tailored treatment options is an unmet need. To unveil the mutational spectrum, whole-exome sequencing of 120 OSCC from male individuals in Taiwan was conducted. Analyzing the contributions of the five mutational signatures extracted from the dataset of somatic variations identified four groups of tumors that were significantly associated with demographic and clinical features. In addition, known (TP53, FAT1, EPHA2, CDKN2A, NOTCH1, CASP8, HRAS, RASA1, and PIK3CA) and novel (CHUK and ELAVL1) genes that were significantly and frequently mutated in OSCC were discovered. Further analyses of gene alteration status with clinical parameters revealed that the tumors of the tongue were enriched with copy-number alterations in several gene clusters containing CCND1 and MAP4K2. Through defining the catalog of targetable genomic alterations, 58% of the tumors were found to carry at least one aberrant event potentially targeted by US Food and Drug Administration (FDA)-approved agents. Strikingly, if targeting the p53-cell cycle pathway (TP53 and CCND1) by the drugs studied in phase I-III clinical trials, those possibly actionable tumors are predominantly located in the tongue, suggesting a better prediction of sensitivity to current targeted therapies. Our work revealed molecular OSCC subgroups that reflect etiological and prognostic correlation as well as defined the landscape of major altered events in the coding regions of OSCC genomes. These findings provide clues for the design of clinical trials for targeted therapies and stratification of OSCC patients with differential therapeutic efficacy.

Identification and evolutionary analysis of long non-coding RNAs in zebra finch.

BACKGROUND: Long non-coding RNAs (lncRNAs) are important in various biological processes, but very few studies on lncRNA have been conducted in birds. To identify IncRNAs expressed during feather development, we analyzed single-stranded RNA-seq (ssRNA-seq) data from the anterior and posterior dorsal regions during zebra finch (Taeniopygia guttata) embryonic development. Using published transcriptomic data, we further analyzed the evolutionary conservation of IncRNAs in birds and amniotes. RESULTS: A total of 1,081 lncRNAs, including 965 intergenic lncRNAs (lincRNAs), 59 intronic lncRNAs, and 57 antisense lncRNAs (lncNATs), were identified using our newly developed pipeline. These avian IncRNAs share similar characteristics with lncRNAs in mammals, such as shorter transcript length, lower exon number, lower average expression level and less sequence conservation than mRNAs. However, the proportion of lncRNAs overlapping with transposable elements in birds is much lower than that in mammals. We predicted the functions of IncRNAs based on the enriched functions of co-expressed protein-coding genes. Clusters of lncRNAs associated with natal down development were identified. The sequences and expression levels of candidate lncRNAs that shared conserved sequences among birds were validated by qPCR in both zebra finch and chicken. Finally, we identified three highly conserved lncRNAs that may be associated with natal down development. CONCLUSIONS: Our study provides the first systematical identification of avian lncRNAs using ssRNA-seq analysis and offers a resource of embryonically expressed lncRNAs in zebra finch. We also predicted the biological function of identified lncRNAs.

Comparative genomics of Vibrio campbellii strains and core species of the Vibrio Harveyi clade.

The core of the Vibrio Harveyi clade contains V. harveyi, V. campbellii, V. owensii, V. jasicida, and V. rotiferianus. They are well recognized aquatic animal pathogens, but misclassification has been common due to similarities in their rDNA sequences and phenotypes. To better understand their evolutionary relationships and functional features, we sequenced a shrimp pathogen strain V. harveyi 1114GL, reclassified it as V. campbellii and compared this and 47 other sequenced Vibrio genomes in the Harveryi clade. A phylogeny based on 1,775 genes revealed that both V. owensii and V. jasicida were closer to V. campbellii than to V. harveyi and that V. campbellii strains can be divided into two distinct groups. Species-specific genes such as intimin and iron acquisition genes were identified in V. campbellii. In particular, the 1114GL strain contains two bacterial immunoglobulin-like genes for cell adhesion with 22 Big_2 domains that have been extensively reshuffled and are by far the most expanded among all species surveyed in this study. The 1114GL strain differed from ATCC BAA-1116 by ~9% at the synonymous sites, indicating high diversity within V. campbellii. Our study revealed the characteristics of V. campbellii in the Harveyi clade and the genetic basis for their wide-spread pathogenicity.