miRNA Precursors Research Articles

Global identification and regulatory network analysis reveal the significant roles of lncRNAs during anther and pollen development in Arabidopsis.

A high-throughput sequencing identified 1283 lncRNAs in anthers at different stages in Arabidopsis and their relationship with protein-coding genes and miRNAs during anther and pollen development were analyzed. Long non-coding RNAs (lncRNAs) are important regulatory molecules involved in various biological processes. However, their roles in male reproductive development and interactions with miRNAs remained elusive. In this study, a high-throughput sequencing of anthers at different developmental stages in Arabidopsis identified 1283 lncRNAs including 524 differentially expressed lncRNAs (DELs). Most of these DELs exhibited positive correlations with the expression patterns of adjacent protein-coding genes. Weighted gene co-expression network analysis (WGCNA) revealed that protein-coding genes targeted by DELs in four modules related to the tetrad stage were associated with functions such as pollen wall formation, pollen germination, or pollen tube growth, respectively. Furthermore, five, 10, and 11 lncRNAs were predicted as miRNAs' endogenous target mimics (eTMs), precursors, and natural antisense transcripts of pri-miRNA, respectively. Remarkably, the lncRNA, host gene of ath-miR167a (ath-miR167aHG), predicted as the precursor of miR167a, was selected for function validation. Its overexpression resulted in the up-regulation of miR167a and the subsequent down-regulation of miR167a's target genes ARF6 and ARF8, demonstrating a functional interaction between ath-miR167aHG and miR167a. The transgenic plants showed delayed flowering, shorter filaments, abnormal anther dehiscence, and undeveloped siliques ultimately, suggesting a role of ath-miR167aHG in male reproductive development. Collectively, our research shed new light on the functions of lncRNAs in male reproductive development and uncovered the unique interactions between lncRNAs and miRNAs.

Chemical shift assignments of DRB2 domains, a dsRNA binding protein in A. thaliana RNAi pathway.

In Arabidopsis thaliana, micro-RNA regulation is primarily controlled by DCL1, an RNase III enzyme, and its associated proteins. DCL1, together with DRB2, governs a specific group of miRNAs that induce the inhibition of target mRNA translation. DRB2 is a multi-domain protein containing two N-terminal dsRNA binding domains (dsRBD) separated by a linker, followed by an unstructured C-terminal tail. The two dsRBDs in DRB2 are involved in recognizing the miRNA precursor and aiding DCL1 in generating 21-nucleotide-long miRNA. Our study presents a nearly complete backbone chemical shift assignment of both dsRBDs and the side-chain assignment of the first dsRBD in DRB2. The data presented here lays the groundwork for future investigations into the structural, dynamic, and functional aspects of DRB2.

Analysis of secondary structure and identification of internal repeats in miRNA precursor sequences of Saccharum officinarum, Saccharum sp. and Sorghum bicolor

Analysis of secondary structure and identification of internal repeats in miRNA precursor sequences of Saccharum officinarum, Saccharum sp. and Sorghum bicolor

PmiRScan: a LightGBM based method for prediction of animal pre-miRNAs.

MicroRNAs (miRNA) are categorized as short endogenous non-coding RNAs, which have a significant role in post-transcriptional gene regulation. Identifying new animal precursor miRNA (pre-miRNA) and miRNA is crucial to understand the role of miRNAs in various biological processes including the development of diseases. The present study focuses on the development of a Light Gradient Boost (LGB) based method for the classification of animal pre-miRNAs using various sequence and secondary structural features. In various pre-miRNA families, distinct k-mer repeat signatures with a length of three nucleotides have been identified. Out of nine different classifiers that have been trained and tested in the present study, LGB has an overall better performance with an AUROC of 0.959. In comparison with the existing methods, our method 'pmiRScan' has an overall better performance with accuracy of 0.93, sensitivity of 0.86, specificity of 0.95 and F-score of 0.82. Moreover, pmiRScan effectively classifies pre-miRNAs from four distinct taxonomic groups: mammals, nematodes, molluscs and arthropods. We have used our classifier to predict genome-wide pre-miRNAs in human. We find a total of 313 pre-miRNA candidates using pmiRScan. A total of 180 potential mature miRNAs belonging to 60 distinct miRNA families are extracted from predicted pre-miRNAs; of which 128 were novel and are note reported in miRBase. These discoveries may enhance our current understanding of miRNAs and their targets in human. pmiRScan is freely available at http://www.csb.iitkgp.ac.in/applications/pmiRScan/index.php .

The expression profile analysis and functional prediction of lncRNAs in peripheral blood mononuclear cells in maintenance hemodialysis patients developing heart failure

Heart failure (HF) is the leading cause of death in patients with maintenance hemodialysis (MHD). Biomarkers has an important guiding role in the early diagnosis, risk stratification, and prognostic assessment of HF. Increasing studies have indicated that long non-coding RNAs (lncRNAs) have played an indispensable role in the regulatory network of HF. This study was aiming to explore the expression profiles of lncRNAs in patients treated with MHD developing heart failure. Peripheral blood mononuclear cells were isolated from 4 hemodialysis patients with reduced ejection fraction (HFrEF) and 4 hemodialysis patients with preserved ejection fraction (HFpEF), respectively. The expression profile analysis of lncRNAs was performed by using Illumina Novaseq 6000 sequencer. Quantitative real time polymerase chain reaction (qRT-PCR) was used to verify the expression of representative differentially expressed lncRNAs. Based on lncRNA-miRNA-mRNA-KEGG network analysis, the potential role of candidate lncRNAs and their association with the severity of HF were further evaluated. In total, 1,429 differentially expressed lncRNAs were found between patients with HFrEF and patients with HFpEF, of which 613 were up-regulated and 816 were down-regulated (P < 0.05). Five candidate lncRNAs were screened out by a series of bioinformatic analyses. After being compared with miRBase, ENST00000561762, one of the 5 candidates, was considered the most likely lncRNA to be serving as a precursor for miRNA. Nine predicted target genes were found by further lncRNA-miRNA-mRNA-KEGG network analysis, and among which ITGB5 was enriched in the actin dynamics signaling pathway. In another cohort of hemodialysis patients, the expression of lncRNA ENST00000561762 was verified by qRT-PCR. Further analysis revealed that there was a strong correlation between left ventricular ejection fraction and ENST00000561762, proBNP, and 6-minute walk distance, respectively. LncRNAs expression profile was remarkably different in hemodialysis patients with HFrEF compared to those with HFpEF. Among which, lncRNA ENST00000561762 was considered as a promising biomarker for patients with HFrEF as it was predicted to be a miRNA precursor to regulate the actin dynamics signaling pathway.

Transcriptomic analysis reveals role of lncRNA LOC100257036 to regulate AGAMOUS during cluster compactness of Vitis vinifera cv. sistan yaghooti

Yaghooti grape, as the earliest grape variety in Iran, is considered as more resistant to heat, drought, and salinity than other cultivars. Cluster compactness is regarded as an inappropriate feature for the productivity of Yaghooti grape as a critical commercial and nutritional product. In plants, lncRNAs play a critical role in regulating biological processes related to growth and development. However, the potential role of lncRNAs was not assessed in cluster compactness. Totally, 1549 lncRNAs were identified by RNA-Seq data analysis in three steps of cluster formation, berry formation, and final cluster size after a thorough screening process. In addition, 229 lncRNAs were differentially expressed in the cluster development steps. Based on the functional analysis, lncRNAs are related to AG and MYB, bHLH, LBD, NAC, and WRKY TFs. Further, the target genes enrichment analysis revealed a relationship between lncRNAs with grape growth and development, as well as resistance to abiotic stresses such as heat and drought, plant defense against pathogens, and early grapes ripening. The study identified four lncRNAs as precursors of miRNAs, predicting that 112 other lncRNAs could potentially be targeted by 166 miRNAs. The results provide new insights into the regulatory functions of lncRNAs in Yaghooti grape to improve overall understanding of the molecular mechanisms related to grape compactness.

AthisomiRDB: A comprehensive database of Arabidopsis isomiRs.

Several pieces of evidence challenge the traditional view of miRNAs as static molecules, revealing dynamic isomiRs originating from each miRNA precursor arm. In plants, isomiRs, which result from imprecise cleavage during pre-miRNA processing and post-transcriptional alterations, serve as crucial regulators of target microRNAs (miRNAs). Despite numerous studies on Arabidopsis miRNAs, the systematic identification and annotation of isomiRs across various tissues and conditions remain limited. Due to the lack of systematically collected isomiR information, we introduce the athisomiRDB database, which houses 20 764 isomiRs from Arabidopsis small RNA-sequencing (sRNA-seq) libraries. It comprises >2700 diverse samples and allows exploration at the sample, miRNA, or isomiR levels, offering insights into the presence or absence of isomiRs. The athisomiRDB includes exclusive and ambiguous isomiRs, each with features such as transcriptional origin, variant-containing isomiRs, and identifiers for frequent single-nucleotide polymorphisms from the 1001 Genomes Project. It also provides 3' nontemplated post-transcriptional additions, isomiR-target interactions, and trait associations for each isomiR. We anticipate that athisomiRDB will play a pivotal role in unraveling the regulatory nature of the Arabidopsis miRNAome and enhancing sRNA research by leveraging isomiR profiles from extensive sRNA-seq datasets. Database URL: https://www.nipgr.ac.in/athisomiRDB.

Characterizing Host microRNA: Virus Interactions of Orthoavulavirus javaense.

Post-transcriptional gene regulation mediated by microRNAs (miRNAs) relies on sequence complementarity between the miRNA seed site and the target gene transcript(s). This complementarity can completely inhibit or reduce translation into protein. We hypothesized that viruses employ sequence complementarity/similarity with host miRNAs to inhibit or increase the miRNA-mediated regulation of host gene expression specifically during viral infection(s). In this study, we focus on Orthoavulavirus javaense (OAVJ), the causative of Newcastle disease, a poultry disease with significant economic impact. A computational analysis of OAVJ genomes from low-virulence (lentogenic) versus virulent (velogenic) viruses was carried out to identify viral signature motifs that potentially either mimic or complement host miRNA seed sequences. Data show that OAVJ genomes harbor viral seed mimics (vSMs) or viral seed sponges (vSSs) and can mimic host miRNAs or inhibit their regulation of host genes, disrupting cellular pathways. Our analyses showed that velogens encode a statistically significant higher number of vSMs and a lower number of vSSs relative to lentogens. The number of vSMs or vSSs did not correlate with gene length. The analysis of the secondary structures flanking these vSMs and vSSs showed structural features common to miRNA precursors. The inhibition or upregulation of vSS-miR-27b-5p altered P gene expression in a sequence-dependent manner. These data demonstrate that viral transcripts can interact with host miRNAs to alter the outcomes of infection.

Ythdf2 facilitates precursor miR-378/miR-378-5p maturation to support myogenic differentiation.

Ythdf2 is known to mediate mRNA degradation in an m6A-dependent manner, and it has been shown to play a role in skeletal muscle differentiation. Recently, Ythdf2 was also found to bind to m6A-modified precursor miRNAs and regulate their maturation. However, it remains unknown whether this mechanism is related to the regulation of myogenesis by Ythdf2. Here, we observed that Ythdf2 knockdown significantly suppressed myotube formation and impacted miRNAs expression during myogenic differentiation. Through integrated analysis of miRNA and mRNA sequencing data, miR-378 and miR-378-5p were identified as important targets of Ythdf2 in myogenesis. Mechanically, Ythdf2 was found to interact with core components of the pre-miRNA processor complex, namely DICER1 and TARBP2, thereby facilitating the maturation of pre-miR-378/miR-378-5p in an m6A-dependent manner and resulting in an increase in the expression levels of mature miR-378 and miR-378-5p. Moreover, the downregulation of either miR-378 or miR-378-5p significantly inhibited myotube formation, while the forced expression of miR-378 or miR-378-5p could partially rescued Ythdf2 knockdown-induced suppression of myogenic differentiation by activating the mTOR pathway. Collectively, our results for the first time suggest that Ythdf2 regulates myogenic differentiation via mediating pre-miR-378/miR-378-5p maturation, which might provide new insights into the molecular mechanisms underlying m6A modification in the regulation of myogenesis.

Description Generation Using Variational Auto-Encoders for Precursor microRNA.

Micro RNAs (miRNA) are a type of non-coding RNA involved in gene regulation and can be associated with diseases such as cancer, cardiovascular, and neurological diseases. As such, identifying the entire genome of miRNA can be of great relevance. Since experimental methods for novel precursor miRNA (pre-miRNA) detection are complex and expensive, computational detection using Machine Learning (ML) could be useful. Existing ML methods are often complex black boxes that do not create an interpretable structural description of pre-miRNA. In this paper, we propose a novel framework that makes use of generative modeling through Variational Auto-Encoders to uncover the generative factors of pre-miRNA. After training the VAE, the pre-miRNA description is developed using a decision tree on the lower dimensional latent space. Applying the framework to miRNA classification, we obtain a high reconstruction and classification performance while also developing an accurate miRNA description.

Distribution Of Microrna Counts Across Human Chromosomes.

microRNAs (miRNAs) are a class of non-coding RNAs that play important roles in gene regulation. miRNAs are transcribed from DNA sequences into primary miRNAs and then processed into precursor miRNAs and mature miRNAs. miRNA gene counts in chromosomes for different species have been studied. Certain chromosomes have higher numbers of miRNA genes in all species, such as the X chromosome, while the Y chromosome has the fewest or no miRNA genes. miRNA counts in different chromosomes might have a positive correlation with coding gene counts in many species. In this study, a regression model was used to find the relationship between the miRNA count and the coding gene count across human chromosomes, and miRNA counts for 23 human chromosomes were predicted based on this regression model. In addition, the chromosome locations for the miRNA biomarkers of major depression, diabetes, Parkinson's disease, and COVID-19 are discussed. The results reveal that miRNA biomarkers of these diseases are located in various chromosomes. The dispersion of miRNA locations across different chromosomes might explain the complication of the pathology of these diseases. Moreover, diabetes and COVID-19 have the largest number of miRNA biomarkers from Chromosome X. As Chromosome X is a sex chromosome, this phenomenon may explain the gender difference in the prevalence or severity of diabetes and COVID-19. The significant gender difference in the prevalence or severity of diabetes and COVID-19 might be due to the regulation function of their miRNA biomarkers from Chromosome X.

MCPIP1 modulates the miRNA‒mRNA landscape in keratinocyte carcinomas

BackgroundMonocyte Chemotactic Protein 1-Induced Protein 1 (MCPIP1, also called Regnase-1) is a negative modulator of inflammation with tumor-suppressive properties. Mice with keratinocyte-specific deletion of the Zc3h12a gene, encoding MCPIP1, (Mcpip1eKO mice) are more susceptible to the development of epidermal papillomas initiated by 7,12-dimethylbenz[a]-anthracene (DMBA) and promoted by 2-O-tetradecanoylphorbol-13-acetate (TPA).MethodsThe aim of this study was to investigate the MCPIP1 RNase-dependent microRNA (miRNA)‒mRNA regulatory network in chemically induced squamous cell carcinoma (SCC)-like skin papillomas. Next-generation sequencing (NGS) coupled with bioinformatic analysis was used to shortlist the MCPIP1-dependent changes in protein-coding genes and miRNAs. The expression levels of the selected miRNAs were analyzed by quantitative PCR in human keratinocytes with MCPIP1 silencing. Functional studies were performed in human keratinocytes transfected with appropriate miRNA mimics. The DIANA-microT-CDS algorithm and DIANA-TarBase v7 database were used to predict potential target genes and identify the experimentally validated targets of differentially expressed (DE) miRNAs.ResultsRNA sequencing (RNA-Seq) analysis of control and Mcpip1eKO DMBA/TPA-induced papillomas revealed transcriptome changes, with 2400 DE protein-coding genes and 33 DE miRNAs. The expression of miR-223-3p, miR-376c-3p, and miR-139-5p was confirmed to be dependent on MCPIP1 activity in both murine and human models. We showed that MCPIP1 directly regulates the expression of miR-376c-3p via direct cleavage of the corresponding precursor miRNA. The pro-proliferative activity of miR-223-3p, miR-376c-3p, and miR-139-5p was experimentally confirmed in SCC-like keratinocytes. Bioinformatic prediction of the mRNA targets of the DE-miRNAs revealed 416 genes as putative targets of the 18 upregulated miRNAs and 425 genes as putative targets of the 15 downregulated miRNAs. Further analyses revealed the murine interactions that are conserved in humans. Functional analysis indicated that during the development of cutaneous SCC, the most important pathways/processes mediated by the miRNA‒mRNA MCPIP1-dependent network are the regulation of inflammatory processes, epithelial cell proliferation, Wnt signaling, and miRNA transcription.ConclusionsLoss of MCPIP1 modulates the expression profiles of 33 miRNAs in chemically induced Mcpip1eKO papillomas, and these changes directly affect the miRNA‒mRNA network and the modulation of pathways and processes related to carcinogenesis.

Elemene as a binding stabilizer of microRNA-145-5p suppresses the growth of non-small cell lung cancer

Elemene is widely recognized as an effective anti-cancer compound and is routinely administered in Chinese clinical settings for the management of several solid tumors, including non-small cell lung cancer (NSCLC). However, its detailed molecular mechanism has not been adequately demonstrated. In this research, it was demonstrated that elemene effectively curtailed NSCLC growth in the patient-derived xenograft (PDX) model. Mechanistically, employing high-throughput screening techniques and subsequent biochemical validations such as microscale thermophoresis (MST), microRNA-145-5p (miR-145-5p) was pinpointed as a critical target through which elemene exerts its anti-tumor effects. Interestingly, elemene serves as a binding stabilizer for miR-145-5p, demonstrating a strong binding affinity (KD = 0.39 ± 0.17 μg/mL) and preventing its degradation both in vitro and in vivo, while not interfering with the synthesis of the primary microRNA transcripts (pri-miRNAs) and precursor miRNAs (pre-miRNAs). The stabilization of miR-145-5p by elemene resulted in an increased level of this miRNA, subsequently suppressing NSCLC progression through the miR-145-5p/mitogen-activated protein kinase kinase kinase 3 (MAP3K3)/nuclear factor kappaB (NF-κB) pathway. Our findings provide a new perspective on revealing the interaction patterns between clinical anti-tumor drugs and miRNAs.

Identification of lncRNAs regulating seed traits in Brassica juncea and development of a comprehensive seed omics database.

Brassica juncea is a crucial oilseed crop, and its seeds possess high economic value as they are a source of edible oil. In order to understand the role of long non coding RNAs (lncRNAs) in the regulation of seed development, we carried out computational analysis using transcriptome data of developing seeds of two contrasting genotypes of B. juncea, Pusajaikisan (PJK) and Early Heera 2 (EH2). The seeds were sampled at three stages, 15, 30, and 45 days after pollination. We identified 1,539 lncRNAs, of which 809 were differentially expressed. We also carried out extensive characterization and functional analysis of seed lncRNAome. The expression patterns were analysed using k-means clustering, and the targets were analysed using pathway, transcription factor, and GO enrichment, as well as ortholog information. We shortlisted a total of 25 robust lncRNA candidates for seed size, oil content, and seed coat color. We also identified 4 lncRNAs as putative precursors of miRNAs regulating seed development. Moreover, a total of 28 miRNA-lncRNA-mRNA regulatory networks regulating seed traits were identified. We also developed a comprehensive database, (BrassIca juncea database or "BIJ" ( https://bij.cuh.ac.in/ ), which provides seed omics as well as other functional genomics and genetics data in an easily accessible form. These candidate lncRNAs are suitable for including in crop improvement programs through molecular breeding, as well as for future validations through genome editing. Together, the knowledge of these candidate lncRNAs and availability of BIJ database shall leverage the crop improvement efforts in B. juncea.

Programmable editing of primary MicroRNA switches stem cell differentiation and improves tissue regeneration

Programmable RNA editing is harnessed for modifying mRNA. Besides mRNA, miRNA also regulates numerous biological activities, but current RNA editors have yet to be exploited for miRNA manipulation. To engineer primary miRNA (pri-miRNA), the miRNA precursor, we present a customizable editor REPRESS (RNA Editing of Pri-miRNA for Efficient Suppression of miRNA) and characterize critical parameters. The optimized REPRESS is distinct from other mRNA editing tools in design rationale, hence enabling editing of pri-miRNAs that are not editable by other RNA editing systems. We edit various pri-miRNAs in different cells including adipose-derived stem cells (ASCs), hence attenuating mature miRNA levels without disturbing host gene expression. We further develop an improved REPRESS (iREPRESS) that enhances and prolongs pri-miR-21 editing for at least 10 days, with minimal perturbation of transcriptome and miRNAome. iREPRESS reprograms ASCs differentiation, promotes in vitro cartilage formation and augments calvarial bone regeneration in rats, thus implicating its potentials for engineering miRNA and applications such as stem cell reprogramming and tissue regeneration.

RNA Sequencing Reveals the Involvement of Serum Exosomal miRNAs in Early Pregnancy in Cattle.

Low fertility is the main cause of the low productivity in beef cattle and is mainly associated with a lack of conception after fertilization. The establishment of early pregnancy in cattle is a complex physiological process, and embryo implantation is crucial for the successful establishment of pregnancy. Exosomal miRNAs play an important role in regulating mammalian embryo implantation and development. This study used synchronous estrus technology to extract exosomes from bovine serum at 0, 14, and 21 days of early pregnancy and analyzed the expression profile of exosomal miRNAs through RNA-seq technology. We identified 472 miRNA precursor sequences and 367 mature miRNA sequences in the three sample groups, with the majority of the miRNAs having high abundance. Differentially expressed miRNAs (DEmiRNAs) were screened, and 20 DEmiRNAs were obtained. The differential expression analysis results show that compared to day 0, there were 15 DEmiRNAs in the serum on day 14 and 5 on day 21 of pregnancy. Compared to the 14th day of pregnancy, there were eight DEmiRNAs in the serum on the 21st day of pregnancy. Bioinformatics analysis shows that the target genes of DEmiRNAs regulated the signaling pathways closely related to early pregnancy, including the VEGF, NF-κB, and MAPK signaling pathways. In addition, the newly discovered miRNAs were bta-miR-3604, bta-miR-2889, bta-miR-3432a, and bta-miR-409b. These results provide a theoretical reference for screening the molecular markers for early pregnancy establishment and maternal recognition of pregnancy (MRP) in cattle and new ideas for shortening the calving interval in cows.

CROSSTALK OF CONSERVATION OF SEQUENCES OF miRNAs AND ENZYMATIC MACHINERY OF miRNAs PRODUCTION IN AMPULLARIIDAE

BACKGROUND: The Ampullariidae family of molluscs is an emerging model for evolutionary studies due to its high diversity, ancient history and wide geographic distribution. miRNAs are essential for the development of the organism, as they help and act in the control of gene expression. The analysis of miRNAs in molluscs, especially in the family Ampullariidae, is especially important due to the low representativeness of analyzed species and the possibility of analyzing the conservation of miRNAs among ampullariids species. OBJECTIVE: Identification and characterization of miRNAs (precursors and matures) and their processing pathway genes. METHODS: Computational prediction and characterization of miRNAs and genes involved in the miRNA pathway were performed using public database of Lanistes nyassanus, Marisa cornuarietis, Pomacea canaliculata and Pomacea maculata. The in silico analysis was performed using a robust algorithm to identify and characterize miRNAs and their precursors in genome of ampullariids species. To search for the putative proteins involved in the miRNA biogenesis the putative proteomes from 4 Ampullariids species and Blastp tool were used. Characterization of conserved protein domains was performed using the PFAM and CDD. Phylogenetic analyzes were performed for the ampullariids miRNA precursors and their orthologs and also for the putative ampullariids proteins involved in the miRNA pathway and their orthologs using MEGA program. FINDINGS: 141 pre-miRNAs and 162 mature miRNAs were identified in the genome of L. nyassanus, 279 pre-miRNAs and 297 mature miRNAs in the genome of M. cornuarietis, 269 pre-miRNAs and 296 mature miRNAs in the genome of P. canaliculata and 299 pre-miRNAs and 316 mature miRNAs in the genome of P. maculata. We identified and characterized 24 putative key proteins involved in the miRNA pathway including Argonaute, DICER, DROSHA and EXPORTIN protein families in the predicted proteome of the 4 ampullariids. The data obtained in this work will support studies of phylogeny, population divergence, speciation and patterns of diversity in the Ampullariidae Family. MAIN CONCLUSIONS: The searching for novel miRNAs and their processing pathway genes in 4 species of ampullariids was able to predict new structures expanding the study of miRNAs in molluscs and in Ampullariidae family, as well as open an avenue to study the roles of miRNAs in the organisms.

Chromosome-scale genome assembly and annotation of Paspalum notatum Flüggé var. saurae

Paspalum notatum Flüggé is an economically important subtropical fodder grass that is widely used in the Americas. Here, we report a new chromosome-scale genome assembly and annotation of a diploid biotype collected in the center of origin of the species. Using Oxford Nanopore long reads, we generated a 557.81 Mb genome assembly (N50 = 56.1 Mb) with high gene completeness (BUSCO = 98.73%). Genome annotation identified 320 Mb (57.86%) of repetitive elements and 45,074 gene models, of which 36,079 have a high level of confidence. Further characterisation included the identification of 59 miRNA precursors together with their putative targets. The present work provides a comprehensive genomic resource for P. notatum improvement and a reference frame for functional and evolutionary research within the genus.

The non-canonically organized members of MIR395 gene family in Brassica juncea are associated with developmentally regulated, sulfate-stress responsive bidirectional promoters that exhibit orientation-dependent differential transcriptional activity

Several MICRORNA genes belonging to same family or different families are often found in homologous or non-homologous clusters. Among the various classes, head-to-head arranged genes form one of the largest categories of non-canonically organized genes. Such head-to-head arranged, non-canonically organized genes possibly share cis-regulatory region with the intergenic sequence having the potential to function as bi-directional promoter (BDP). The transcriptional regulation of head-to-head arranged genes, especially with bidirectional promoters, remains an enigma. In the past, bidirectional promoters have been characterized for a small set of protein-coding gene pairs in plants; however, to the best of our knowledge, no such study has been carried so far for MICRORNA genes. The present study thus functionally characterizes bidirectional promoters associated with members of MIR395 family, which is evolutionary conserved and is most frequently occurring cluster across plant kingdom.In Arabidopsis thaliana, the MIR395 gene family contains six members with two head-to-head arranged gene pairs- MIR395A-B and MIR395E-F. This organization was found to be conserved at seven loci for MIR395A-B, and eleven loci for MIR395E-F in five Brassica sps. Sequence analysis of the putative bidirectional promoters revealed variation in length, GC content and distribution of strict TATA-box. Comparatively higher level of conservation at both the ends of the bidirectional promoters, corresponding to ca. 250 bp upstream of 5’end of the respective MIRNA precursor, was observed. These conserved regions harbour several abiotic stress (nutrient, salt, drought) and hormone (ABA, ethylene) responsive cis-motifs. Functional characterization of putative bidirectional promoters associated with MIR395A-B and MIR395E-F from Arabidopsis and their respective orthologs from Brassica juncea (Bj_A08 MIR395A-B, Bj_B03 MIR395A-B, Bj_A07.1 MIR395E-F and Bj_A07.2 MIR395E-F) was carried out using a dual-reporter vector with β-glucuronidase (GUS) and Green Fluorescent Protein (GFP). Analysis of transcriptional regulation of the two reporter genes - GUS and GFP during developmental stages confirmed their bidirectional nature. Orientation-dependent differential reporter activity indicated asymmetric nature of the promoters. Comparison of the reporter activity amongst orthologs, paralogs and homeologs revealed regulatory diversification, an outcome expected in polyploid genomes. Interestingly, reporter gene activities driven by selected bidirectional promoters were also observed in anther and siliques apart vegetative tissues indicating role of miR395 in anther and fruit development. Finally, we evaluated the activity of reporter genes driven under transcriptional regulation of bidirectional promoters under normal and sulfate-deprived conditions which revealed asymmetric inducibility under sulfate-starvation, in agreement with the known role of miR395 in sulfate homeostasis.

Widespread changes to the translational landscape in a maize microRNA biogenesis mutant.

MicroRNAs are short, non-coding RNAs that repress gene expression in both plants and animals and have diverse functions related to growth, development, and stress responses. The ribonuclease, DICER-LIKE1 (DCL1) is required for two steps in plant miRNA biogenesis: cleavage of the primary miRNAs (pri-miRNAs) to release a hairpin structure, called the precursor miRNA (pre-miRNA) and cleavage of the pre-miRNA to generate the miRNA/miRNA* duplex. The mature miRNA guides the RNA-induced silencing complex to target RNAs with complementary sequences, resulting in translational repression and/or RNA cleavage of target mRNAs. However, the relative contribution of translational repression versus mRNA degradation by miRNAs remains unknown at the genome-level in crops, especially in maize. The maize fuzzy tassel (fzt) mutant contains a hypomorphic mutation in DCL1 resulting in broad developmental defects. While most miRNAs are reduced in fzt, the levels of miRNA-targeted mRNAs are not dramatically increased, suggesting that translational regulation by miRNAs may be common. To gain insight into the repression mechanism of plant miRNAs, we combined ribosome profiling and RNA-sequencing to globally survey miRNA activities in maize. Our data indicate that translational repression contributes significantly to regulation of most miRNA targets and that approximately one-third of miRNA targets are regulated primarily at the translational level. Surprisingly, ribosomes appear altered in fzt mutants suggesting that DCL1 may also have a role in ribosome biogenesis. Thus, DICER-LIKE1 shapes the translational landscape in plants through both miRNA-dependent and miRNA-independent mechanisms.