Characterization Of Small RNAs Research Articles

Characterization of small RNAs in the spleen of MASH in a non-human primate model

Metabolic dysfunction-associated steatotic liver disease (MASLD) and its advanced stage, metabolic dysfunction-associated steatohepatitis (MASH), are increasingly recognized as a global health issue. This study examines the role of small RNAs in the spleen of MASH using a non-human primate model. We performed high-throughput small RNA sequencing on spleen tissues from MASH-primates, revealing significant alterations in the expression of small non-coding RNAs, especially miRNAs. Notably, miR-96, miR-182, miR-183, and miR-122 showed differential expression in MASH spleens. Predictive and validation studies have identified potential target genes, such as PTX3 and NFIX, that were significantly dysregulated in spleens of MASH. These findings characterized small RNAs in spleen of MASH and offer a novel insight for further research for MASH.

Characterization of small RNAs in early zebrafish PGCs.

Characterization of small RNAs in early zebrafish PGCs.

Comparison of methods and characterization of small RNAs from plasma extracellular vesicles of HIV/HCV coinfected patients

Hepatitis C virus (HCV) and human immunodeficiency virus (HIV) hijack the host exosomal machinery as an additional mechanism of infection and evasion of the immune system, modifying the small RNA (smRNA) cargo during infection. We characterized the surface epitopes of extracellular vesicles (EVs) from plasma HIV/HCV-coinfected patients and their smRNA cargo profile, by comparing different isolation procedures. Six EVs isolation procedures were compared: ultracentrifugation, and five different polyethylene glycol-based methods (commercial, combined with a column purification step and two custom); and two RNA commercial kits (phenol and non-phenol based) were used. High-throughput sequencing of smRNAs was performed. Exosomal surface epitopes were analyzed by the MACSPlex Exosome Kit. Four miRNAs displayed differences among protocols (hsa-miR-205-5p and hsa-let-7a/b/f-5p). The selection of RNA isolation kit impacted on the detection of miRNAs and other smRNAs, where the phenol-based RNA isolation kit performed acceptably. EVs surface was enriched with HLA-DR/DP/DQ, CD81, and CD8. There were three liver-specific miRNAs overexpressed (let-7a-5p, miR-21-5p and hsa-miR-122-5p), thus, EVs cargo might reflect liver disease evolution. Other smRNAs such as piwi-interacting RNAs were also detected for the first time. Custom polyethylene glycol precipitation-based methods combined with an RNA phenol-based kit yielded the higher number of smRNAs for EVs isolated from plasma HIV/HCV patients.

Inventory of European Sea Bass (Dicentrarchus labrax) sncRNAs Vital During Early Teleost Development.

During early animal ontogenesis, a plethora of small non-coding RNAs (sncRNAs) are greatly expressed and have been shown to be involved in several regulatory pathways vital to proper development. The rapid advancements in sequencing and computing methodologies in the last decade have paved the way for the production of sequencing data in a broad range of organisms, including teleost species. Consequently, this has led to the discovery of sncRNAs as well as the potentially novel roles of sncRNA in gene regulation. Among the several classes of sncRNAs, microRNAs (miRNAs) have, in particular, been shown to play a key role in development. The present work aims to identify the miRNAs that play important roles during early European sea bass (Dicentrarchus labrax) development. The European sea bass is a species of high commercial impact in European and especially Mediterranean aquaculture. This study reports, for the first time, the identification and characterization of small RNAs that play a part in the 10 developmental stages (from morula to all fins) of the European sea bass. From 10 developmental stages, more than 135 million reads, generated by next-generation sequencing, were retrieved from publicly available databases as well as newly generated. The analysis resulted in about 2,000 sample grouped reads, and their subsequently annotation revealed that the majority of transcripts belonged to the class of miRNAs followed by small nuclear RNAs and small nucleolar RNAs. The analysis of small RNA expression among the developmental stages under study revealed that miRNAs are active throughout development, with the main activity occurring after the earlier stages (morula and 50% epiboly) and at the later stages (first feeding, flexion, and all fins). Furthermore, investigating miRNAs exclusively expressed in one of the stages unraveled five miRNAs with a higher abundance only in the morula stage (miR-155, miR-430a, d1, d2, and miR-458), indicating possible important key roles of those miRNAs in further embryonic development. An additional target search showed putative miRNA-mRNA interactions with possible direct and indirect regulatory functions of the identified miRNAs.

Existence of Diverse Modifications in Small-RNA Species Composed of 16-28 Nucleotides.

RNA contains diverse modifications that exert an important influence in a variety of cellular processes. So far, more than 150 modifications have been identified in various RNA species, mainly in ribosomal RNA (rRNA), transfer RNA (tRNA), and messenger RNA (mRNA). In contrast to rRNA, tRNA, and mRNA, the known modifications in small RNA species have been primarily limited to 2'-O-ribose methylation in plants and inosine in mammals. The methylation of small RNAs in mammals is still unclear. Current methods widely used in the characterization of small RNAs are mainly based on the strategy of nucleic acid hybridization and sequencing, which cannot characterize modifications in small RNAs. Herein, we have systematically investigated modifications in small RNAs composed of 16-28 nucleotides (nt) by establishing an effective isolation and neutral enzymatic digestion of small RNAs in combination with liquid chromatography/electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). This method allowed us to simultaneously detect 57 different types of nucleoside modification. By using this approach, we revealed 24 modifications in small RNAs comprising 16-28 nt from human cells. In addition, we found that the obesity-associated protein (FTO) may demethylate N6 -methyladenosine (m6 A) and N6 ,2'-O-dimethyladenosine (m6 Am) in small RNAs of 16-28 nt. Our study demonstrates the existence of diverse modifications in small RNAs composed of 16-28 nt, which may promote in-depth understanding of the regulatory roles of noncoding RNAs.

Comparative characterization of small RNAs derived from an emaravirus and a geminivirus infecting pigeonpea

High throughput sequencing technologies, supported by bioinformatics tools are employed to retrieve small RNA sequence information derived from the nucleic acids of plant infecting viruses. In addition to characterization of the small RNAs to understand the biology of the virus, the small RNA sequence can be assembled to reconstitute viral genome sequence. For the first time the semiconductor based Ion Proton sequencing technology is used to sequence the small RNAs from pigeonpea (Cajanus cajan) plants infected by two distinct viruses with RNA and DNA as their genomes. The reconstitution of the viral genome sequence revealed that the pigeonpea plant from Kalaburagi (erstwhile Gulbarga, Karnataka state) was infected by an emaravirus species Pigeonpea sterility mosaic emaravirus 1 (PPSMV-1) and another plant from New Delhi was infected by a begomovirus species Mungbean yellow mosaic India virus (MYMIV). Characterization and comparison of small RNA sequences derived from both the viruses showed vast differences in their pattern of accumulation and their size classes. In the case of PPSMV-1, the 21 nt sized siRNAs accumulated at far greater levels followed by 22 and 24 nt siRNAs. Whereas in MYMIV, the proportion of accumulation of each size class of siRNAs was similar. Further the distribution of small RNAs across the genomes of PPSMV-1 and MYMIV was mapped and the density of small RNA accumulation showed a positive correlation with the GC content of viral sequence.

Primary Characterization of Small RNAs in Symbiotic Nitrogen-Fixing Bacteria.

High-throughput transcriptome profiling (RNAseq) has uncovered large and heterogeneous populations of small noncoding RNA species (sRNAs) with potential regulatory roles in bacteria. A large fraction of sRNAs are differentially regulated and rely on protein-assisted antisense interactions to trans-encoded target mRNAs to fine-tune posttranscriptional reprogramming of gene expression in response to external cues. However, annotation and function of sRNAs are still largely overlooked in nonmodel bacteria with complex lifestyles. Here, we describe experimental protocols successfully applied for the accurate annotation, expression profiling and target mRNA identification of trans-acting sRNAs in the nitrogen-fixing α-rhizobium Sinorhizobium meliloti. The protocols presented here can be similarly applied for the characterization of trans-sRNAs in genetically tractable α-proteobacteria of agronomical or clinical relevance interacting with eukaryotic hosts.

Genome-wide identification and characterization of small RNAs in Rhodobacter capsulatus and identification of small RNAs affected by loss of the response regulator CtrA

ABSTRACTSmall non-coding RNAs (sRNAs) are involved in the control of numerous cellular processes through various regulatory mechanisms, and in the past decade many studies have identified sRNAs in a multitude of bacterial species using RNA sequencing (RNA-seq). Here, we present the first genome-wide analysis of sRNA sequencing data in Rhodobacter capsulatus, a purple nonsulfur photosynthetic alphaproteobacterium. Using a recently developed bioinformatics approach, sRNA-Detect, we detected 422 putative sRNAs from R. capsulatus RNA-seq data. Based on their sequence similarity to sRNAs in a sRNA collection, consisting of published putative sRNAs from 23 additional bacterial species, and RNA databases, the sequences of 124 putative sRNAs were conserved in at least one other bacterial species; and, 19 putative sRNAs were assigned a predicted function. We bioinformatically characterized all putative sRNAs and applied machine learning approaches to calculate the probability of a nucleotide sequence to be a bona fide sRNA. The resulting quantitative model was able to correctly classify 95.2% of sequences in a validation set. We found that putative cis-targets for antisense and partially overlapping sRNAs were enriched with protein-coding genes involved in primary metabolic processes, photosynthesis, compound binding, and with genes forming part of macromolecular complexes. We performed differential expression analysis to compare the wild type strain to a mutant lacking the response regulator CtrA, an important regulator of gene expression in R. capsulatus, and identified 18 putative sRNAs with differing levels in the two strains. Finally, we validated the existence and expression patterns of four novel sRNAs by Northern blot analysis.

Profiling and Characterization of Small RNAs in the Liverwort, Marchantia polymorpha, Belonging to the First Diverged Land Plants.

MicroRNAs (miRNAs) have important roles in gene regulation during plant development. Previous studies revealed that some miRNAs are highly shared by most land plants. Recently, the liverwort, Marchantia polymorpha, has been studied by molecular genetic approaches, and sequencing of its genome is currently underway. The expression pattern and the detailed functions of miRNAs during Marchantia development are unknown. Here, we profiled the small RNAs expressed in thalli, antheridiophores and archegoniophores of M. polymorpha using high-throughput RNA sequencing. We revealed that a limited number of miRNAs are shared between M. polymorpha and the moss, Physcomitrella patens, and that a number of miRNAs are M. polymorpha specific. Like other land plants, cognate target genes corresponding to conserved miRNAs could be found in the genome database and were experimentally confirmed to guide cleavage of target mRNAs. The results suggested that two genes in the SPL (SQUAMOSA PROMOTER BINDING-LIKE) transcription factor family, which are regulated by miR156 in most land plants, were instead targeted by two distinct miRNAs in M. polymorpha. In order to demonstrate the physiological roles of miRNAs in M. polymorpha, we constructed an miRNA ectopic expression system to establish overexpression transformants for conserved miRNAs, miR166 and miR319. Ectopic expression of these miRNAs induced abnormal development of the thallus and gemma cups, suggesting that balanced expression of miRNA/target mRNAs has a crucial role in developmental regulation in M. polymorpha. Profiling data on miRNA together with the ectopic expression system would provide new information on the liverwort small RNA world and evolutionary divergence/conservation of small RNA function among land plants.

Characterization of Small RNAs and Their Targets from Fusarium oxysporum Infected and Noninfected Cotton Root Tissues

Genes for host-plant resistant do exist in cotton (Gossypium spp.) but improvement of cotton cultivars with resistance is difficult due to intensive breeding. Identifying molecular-genetic mechanisms associated with disease resistance can offer a new way to combat a serious threat such as Fusarium oxysporum f. sp. vasinfectum (FOV). Here, we captured and annotated “top-layer” of abundantly and specifically expressed cotton root small RNA (sRNA) including microRNA (miR) sequences during FOV pathogenesis using size-directed and adenylated linker-based sRNA cloning strategy. A total of 4116 candidate sRNA sequences with 16 to 30 nucleotide (nt) length were identified from four complementary DNA (cDNA) libraries of noninfected and FOV race 3-infected roots of susceptible (“11970”) versus resistant (“Mebane B-1”) cotton genotypes (G. hirsutum L.). The highest numbers of sRNA signatures were those with 19–24 nt long in all libraries, and interestingly, the number of sRNAs substantially increased during FOV infection in a resistant genotype, while it sharply decreased in a susceptible genotype. In BLAST analysis, more than 73 % of sRNAs matched Gossypium (G. arboretum L., G. hirsutum, and G. barbadense L.) ESTs. A small percentage of sRNAs matched A. thaliana (1.68 %), T. cacao (1.26 %), fungal (2 %), and other organism (21.33 %) ESTs. mirBase comparisons showed that 4 % of sRNAs were homologous to previously reported plant miRs, among which we predicted novel cotton Ghr-miR-160 that was not registered in the cotton miR database. These major representative sRNA signatures targeted proteins associated with the key biological processes and molecular functions, explaining the molecular mechanisms of the host defense response during the FOV pathogenesis in cotton.

Small RNA Detection by in Situ Hybridization Methods.

Small noncoding RNAs perform multiple regulatory functions in cells, and their exogenous mimics are widely used in research and experimental therapies to interfere with target gene expression. MicroRNAs (miRNAs) are the most thoroughly investigated representatives of the small RNA family, which includes short interfering RNAs (siRNAs), PIWI-associated RNA (piRNAs), and others. Numerous methods have been adopted for the detection and characterization of small RNAs, which is challenging due to their short length and low level of expression. These include molecular biology methods such as real-time RT-PCR, northern blotting, hybridization to microarrays, cloning and sequencing, as well as single cell miRNA detection by microscopy with in situ hybridization (ISH). In this review, we focus on the ISH method, including its fluorescent version (FISH), and we present recent methodological advances that facilitated its successful adaptation for small RNA detection. We discuss relevant technical aspects as well as the advantages and limitations of ISH. We also refer to numerous applications of small RNA ISH in basic research and molecular diagnostics.

Comprehensive discovery and characterization of small RNAs in Corynebacterium glutamicumATCC 13032

BackgroundRecent discoveries on bacterial transcriptomes gave evidence that small RNAs (sRNAs) have important regulatory roles in prokaryotic cells. Modern high-throughput sequencing approaches (RNA-Seq) enable the most detailed view on transcriptomes offering an unmatched comprehensiveness and single-base resolution. Whole transcriptome data obtained by RNA-Seq can be used to detect and characterize all transcript species, including small RNAs. Here, we describe an RNA-Seq approach for comprehensive detection and characterization of small RNAs from Corynebacterium glutamicum, an actinobacterium of high industrial relevance and model organism for medically important Corynebacterianeae, such as C. diphtheriae and Mycobacterium tuberculosis.ResultsIn our RNA-Seq approach, total RNA from C. glutamicum ATCC 13032 was prepared from cultures grown in minimal medium at exponential growth or challenged by physical (heat shock, cold shock) or by chemical stresses (diamide, H2O2, NaCl) at this time point. Total RNA samples were pooled and sequencing libraries were prepared from the isolated small RNA fraction. High throughput short read sequencing and mapping yielded over 800 sRNA genes. By determining their 5′- and 3′-ends and inspection of their locations, these potential sRNA genes were classified into UTRs of mRNAs (316), cis-antisense sRNAs (543), and trans-encoded sRNAs (262). For 77 of trans-encoded sRNAs significant sequence and secondary structure conservation was found by a computational approach using a whole genome alignment with the closely related species C. efficiens YS-314 and C. diphtheriae NCTC 13129. Three selected trans-encoded sRNAs were characterized by Northern blot analysis and stress-specific transcript patterns were found.ConclusionsThe study showed comparable numbers of sRNAs known from genome-wide surveys in other bacteria. In detail, our results give deep insight into the comprehensive equipment of sRNAs in C. glutamicum and provide a sound basis for further studies concerning the functions of these sRNAs.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-14-714) contains supplementary material, which is available to authorized users.

Characterization of small RNAs and their target genes in wheat seedlings using sequencing-based approaches

Wheat is the most highly cultivated plant species for its grain production throughout the world. Because small RNA-dependent gene regulation is critical for successful completion of plant life cycle including its productivity, identification of not only miRNAs but also confirming their targets in wheat is important. To identify small RNAs including novel miRNAs as well as miRNA targets in wheat, we constructed small RNA and degradome libraries from wheat seedlings. Small RNA analysis resulted in identification of most conserved miRNAs including novel miRNAs that can be grouped into 32 miRNA families. The sequence analysis also led to the characterization of two abundantly expressed rRNA-derived small RNAs. To identify miRNA targets, degradome library was sequenced and the bioinformatic analysis confirmed 53 genes as targets for miRNAs and Tas3-siRNAs. Degradome analysis also confirmed a conserved fine-tuning mechanism of Tas3-siRNA abundance by siRNA-mediated silencing of TAS3 transcripts in diverse plant species. These findings added additional information to the small RNA knowledge-base in wheat.

Identification and Characterization of Small RNAs in the Hyperthermophilic Archaeon Sulfolobus solfataricus

The term RNA silencing (RNA interference, RNAi) describes a set of mechanisms that regulate gene expression in eukaryotes. Small interfering RNAs (siRNA) and microRNAs (miRNAs) are two major types of RNAi-associated small RNAs (smRNAs) found in most eukaryotic organisms. Despite the presence of a plethora of non-coding RNAs longer than 50-nucleotide (nt) in length in various species of Archaea, little is known about smRNAs in archaea that resemble the 20–24-nt long smRNAs found in eukaryotes, which have been implicated in the post-transcriptional control of gene expression. Here, we report the finding of a large number of smRNAs approximatelly 20-nt in length, including phased smRNAs and potential miRNAs, from the hyperthermophilic archaeon Sulfolobus solfataricus p2 (Ssp2) based on deep sequencing. The expression of some of the miRNA candidates in Ssp2 was confirmed. Consistent with the Ssp2 hyperthermophilic properties, we found that higher temperatures more efficiently induced the production of the miRNA candidates in an in vitro system using the putative foldback precursor transcripts incubated with Ssp2 extract. Although we initially predicted putative target genes of some miRNA candidates, further analysis mapped the cleavage sites downstream of the miRNA candidate complementary regions, similar to those involved in plant miRNA-mediated TAS transcript cleavage. We also identified smRNAs from clustered, regularly interspaced, short palindromic repeat (CRISPR) loci, which play important roles in prokaryotic microbial defense systems. Archaea represent a unique life form next to Bacteria and Eukarya, and our results may provide a useful resource for further in-depth study on the regulation and evolution of smRNAs in this special organism.

Characterization of small RNAs from Ulva prolifera by high-throughput sequencing and bioinformatics analysis

The seaweed Ulva prolifera exists in 2 different states; attached to rocks or free-floating. However, there is little difference between the structures of the 2 states. U. prolifera thalli show significant differences in growth rate, with the attached thalli growing at a normal rate and free-floating thalli growing at a much faster rate. This raised the possibility that the growth of the two states may be regulated differently. miRNAs are important post-transcriptional regulators. In higher plants and animals, miRNAs have been extensively studied but they have been rarely studied in algae. To identify U. prolifera miRNAs and to investigate their possible roles in proliferation, we constructed and sequenced small RNA (sRNA) libraries from U. prolifera. Our results show that U. prolifera has a complex small RNA system that might play important roles in various processes.

Cloning and bioinformatic identification of small RNAs in the filarial nematode, Brugia malayi

Characterization of small RNAs from the filarial nematode Brugia malayi is the initial step in understanding their role in gene silencing. Both RNA cloning and bioinformatics were used to identify 32 microRNAs (miRNAs) belonging to 24 families. One family, miR-36 only occurs in helminths including B. malayi. Several of the miRNAs are arranged in clusters and are coordinately expressed as determined by northern blot analysis. In addition, small RNAs were identified from Pao/Bleo retrotransposons and their associated repeat sequences indicating that B. malayi uses an RNAi mechanism to maintain genome integrity. Analysis of these data provides a first glimpse into how small RNA-mediated silencing pathways regulate the parasitic life cycle of B. malayi.

Characterization of Small RNAs in Aplysia Reveals a Role for miR-124 in Constraining Synaptic Plasticity through CREB

Memory storage and memory-related synaptic plasticity rely on precise spatiotemporal regulation of gene expression. To explore the role of small regulatory RNAs in learning-related synaptic plasticity, we carried out massive parallel sequencing to profile the small RNAs of Aplysia californica. We identified 170 distinct miRNAs, 13 of which were novel and specific to Aplysia. Nine miRNAs were brain enriched, and several of these were rapidly downregulated by transient exposure to serotonin, a modulatory neurotransmitter released during learning. Further characterization of the brain-enriched miRNAs revealed that miR-124, the most abundant and well-conserved brain-specific miRNA, was exclusively present presynaptically in a sensory-motor synapse where it constrains serotonin-induced synaptic facilitation through regulation of the transcriptional factor CREB. We therefore present direct evidence that a modulatory neurotransmitter important for learning can regulate the levels of small RNAs and present a role for miR-124 in long-term plasticity of synapses in the mature nervous system.

Cloning and characterization of small RNAs from Medicago truncatula reveals four novel legume‐specific microRNA families

MicroRNAs (miRNAs) and small-interfering RNAs (siRNAs) have emerged as important regulators of gene expression in higher eukaryotes. Recent studies indicate that genomes in higher plants encode lineage-specific and species-specific miRNAs in addition to the well-conserved miRNAs. Leguminous plants are grown throughout the world for food and forage production. To date the lack of genomic sequence data has prevented systematic examination of small RNAs in leguminous plants. Medicago truncatula, a diploid plant with a near-completely sequenced genome has recently emerged as an important model legume. We sequenced a small RNA library generated from M. truncatula to identify not only conserved miRNAs but also novel small RNAs, if any. Eight novel small RNAs were identified, of which four (miR1507, miR2118, miR2119 and miR2199) are annotated as legume-specific miRNAs because these are conserved in related legumes. Three novel transcripts encoding TIR-NBS-LRR proteins are validated as targets for one of the novel miRNA, miR2118. Small RNA sequence analysis coupled with the small RNA blot analysis, confirmed the expression of around 20 conserved miRNA families in M. truncatula. Fifteen transcripts have been validated as targets for conserved miRNAs. We also characterized Tas3-siRNA biogenesis in M. truncatula and validated three auxin response factor (ARF) transcripts that are targeted by tasiRNAs. These findings indicate that M. truncatula and possibly other related legumes have complex mechanisms of gene regulation involving specific and common small RNAs operating post-transcriptionally.

Identification and characterization of small RNAs from the phloem of Brassica napus

Systemic signalling is indispensable for the coordination of diverse physiological processes during development, defence and nutrient allocation. Indirect evidence suggests that plant small RNAs (smRNAs) could be involved in long-distance information transfer via the vasculature of the plant. Analyses of the smRNA complements of vascular exudates from oilseed rape (Brassica napus) showed that xylem sap is devoid of RNA, whereas phloem sap contained a large number of smRNAs. In addition to 32 annotated microRNAs (miRNAs) from 18 different families that could be identified and approved, a set of unknown smRNAs, predominantly of 21 and 24 nucleotides in length, was obtained, and selected candidates were found to be highly abundant in phloem sap. Moreover, we could demonstrate that the levels of three miRNAs known to respond to nutrient deprivation in non-vascular tissue, miR395 (sulphate), miR398 (copper) and miR399 (phosphate), were increased in phloem sap during the growth of plants under the respective starvation conditions. Interestingly, only mature miRNA molecules were found to be stress responsive, demonstrating that single-stranded sense miRNAs are most likely to represent the physiologically relevant molecules. The strong responses in the phloem suggest a role of miRNAs in systemic information transfer via this long-distance transport system.

Identification and characterization of small RNAs from vernalizedArabidopsis thaliana

MicroRNAs (miRNAs) and small interfering RNAs (siRNAs) are two major classes of small non-coding RNAs with important roles in the regulation of gene expression, such as mRNA degradation and translational repression, heterochromatin formation, genome defense against transposons and viruses in eukaryotes. MiRNA- and siRNA-directed processes have emerged as a regulatory mechanism for growth and development in both animals and plants. To identify small RNAs that might be involved in vernalization, a process accelerating flowering brought on by a long period of cold, we generated a library of small RNAs from Arabidopsis that had been subject to vernalization. From the analysis of the library, 277 small RNAs were identified. They were distributed throughout all the five chromosomes. While the vast majority of small RNA genes locate on intergenic regions, others locate on repeat-rich regions, centromeric regions, transposon-related genes, and protein-coding genes. Five of them were mapped to convergent overlapping gene pairs. Two-hundred and forty of them were novel endogenous small RNAs that have not been cloned yet from plants grown under normal conditions and other environmental stresses. Seven putative miRNAs were up- or down-regulated by vernalization. In conclusion, many small RNAs were identified from vernalized Arabidopsis and some of these identified small RNAs may play roles in plant responses to vernalization.