Imaging Single mRNA Molecules in Mammalian Cells Using an Optimized MS2-MCP System

G3BP1 ribonucleoprotein complexes regulate focal adhesion protein mobility and cell migration

The subcellular localization of mRNAs plays a pivotal role in biological processes, including cell migration. For instance, β-actin mRNA and its associated RNA-binding protein (RBP), ZBP1/IGF2BP1, are recruited to focal adhesions (FAs) to support localized β-actin synthesis, crucial for cell migration. However, whether other mRNAs and RBPs also localize at FAs remains unclear. Here, we identify hundreds of mRNAs that are enriched at FAs (FA-mRNAs). FA-mRNAs share characteristics with stress granule (SG) mRNAs and are found in ribonucleoprotein (RNP) complexes with the SG RBP. Mechanistically, G3BP1 binds to FA proteins in an RNA-dependent manner, and its RNA-binding and dimerization domains, essential for G3BP1 to form RNPs in SG, are required for FA localization and cell migration. We find that G3BP1 RNPs promote cell speed by enhancing FA protein mobility and FA size. These findings suggest a previously unappreciated role for G3BP1 RNPs in regulating FA function under non-stress conditions.

Advances in posterity of visualization in paradigm of nano‐level ultra‐structures for nano–bio interaction studies

The progression in contemporary scientific field is facilitated by a multitude of sophisticated and cutting‐edge methodologies that are employed for various research purposes. Among these methodologies, microscopy stands out as a fundamental and essential technique utilized in scientific investigations. Moreover, due to the continuous evolution and enhancement of microscopic methodologies, nanotechnology has reached a highly developed stage within modern scientific realm, particularly renowned for its wide‐ranging applications in the fields of biomedicine and environmental science. When it comes to conducting comprehensive and in‐depth experimental analyses to explore the nanotechnological aspects relevant to biological applications, the concept of nano–biological interaction emerges as the focal point of any research initiative. Nonetheless, this particular study necessitates a meticulous approach toward imaging and visualization at diverse magnification levels to ensure accurate observations and interpretations. It is widely acknowledged that modern microscopy has emerged as a sophisticated and invaluable instrument in this regard. This review aims to provide a comprehensive discussion on the progress made in microscopic techniques specifically tailored for visualizing the interactions between nanostructures and biological entities, thereby facilitating the exploration of the practical applications of nanotechnology in the realm of biological sciences.

Cellular heterogeneity in TNF/TNFR1 signalling: live cell imaging of cell fate decisions in single cells

Cellular responses to TNF are inherently heterogeneous within an isogenic cell population and across different cell types. TNF promotes cell survival by activating pro-inflammatory NF-κB and MAPK signalling pathways but may also trigger apoptosis and necroptosis. Following TNF stimulation, the fate of individual cells is governed by the balance of pro-survival and pro-apoptotic signalling pathways. To elucidate the molecular mechanisms driving heterogenous responses to TNF, quantifying TNF/TNFR1 signalling at the single-cell level is crucial. Fluorescence live-cell imaging techniques offer real-time, dynamic insights into molecular processes in single cells, allowing for detection of rapid and transient changes, as well as identification of subpopulations, that are likely to be missed with traditional endpoint assays. Whilst fluorescence live-cell imaging has been employed extensively to investigate TNF-induced inflammation and TNF-induced cell death, it has been underutilised in studying the role of TNF/TNFR1 signalling pathway crosstalk in guiding cell-fate decisions in single cells. Here, we outline the various opportunities for pathway crosstalk during TNF/TNFR1 signalling and how these interactions may govern heterogenous responses to TNF. We also advocate for the use of live-cell imaging techniques to elucidate the molecular processes driving cell-to-cell variability in single cells. Understanding and overcoming cellular heterogeneity in response to TNF and modulators of the TNF/TNFR1 signalling pathway could lead to the development of targeted therapies for various diseases associated with aberrant TNF/TNFR1 signalling, such as rheumatoid arthritis, metabolic syndrome, and cancer.

Measuring Transcription Dynamics of Individual Genes Inside Living Cells

Transcription is a highly dynamic process, which, for many genes, occurs in stochastic bursts. Studying what regulates these stochastic bursts requires visualization and quantification of transcription dynamics in single living cells. Such measurements of bursting can be accomplished by labeling nascent transcripts of single genes fluorescently with the MS2 and PP7 RNA labeling techniques. Live-cell single-molecule microscopy of transcription in real time allows for the extraction of transcriptional bursting kinetics inside single cells. This chapter describes how to set up the MS2 or PP7 RNA labeling system of endogenous genes in both budding yeast (Saccharomyces cerevisiae) and mammalian cells (mouse embryonic stem cells). We include how to genetically engineer the cells with the MS2 and PP7 system, describe how to perform the live-microscopy experiments and discuss how to extract transcriptional bursting parameters of the genes of interest.

Analysis and Modeling of Early Estradiol-induced GREB1 Single Allele Gene Transcription at the Population Level

Single molecule fluorescence in situ hybridization (smFISH) can be used to visualize transcriptional activation at the single allele level. We and others have applied this approach to better understand the mechanisms of activation by steroid nuclear receptors. However, there is limited understanding of the interconnection between the activation of target gene alleles inside the same nucleus and within large cell populations. Using the GREB1 gene as an early estrogen receptor (ER) response target, we applied smFISH to track E2-activated GREB1 allelic transcription over early time points to evaluate potential dependencies between alleles within the same nucleus. We compared two types of experiments where we altered the initial status of GREB1 basal transcription by treating cells with and without the elongation inhibitor flavopiridol (FV). E2 stimulation changed the frequencies of active GREB1 alleles in the cell population independently of FV pre-treatment. In FV treated cells, the response time to hormone was delayed, albeit still reaching at 90 minutes the same levels as in cells not treated by FV. We show that the joint frequencies of GREB1 activated alleles observed at the cell population level imply significant dependency between pairs of alleles within the same nucleus. We identify probabilistic models of joint alleles activations by applying a principle of maximum entropy. For pairs of alleles, we have then quantified statistical dependency by computing their mutual information. We have then introduced a stochastic model compatible with allelic statistical dependencies, and we have fitted this model to our data by intensive simulations. This provided estimates of the average lifetime for degradation of GREB1 introns and of the mean time between two successive transcription rounds. Our approach informs on how to extract information on single allele regulation by ER from within a large population of cells, and should be applicable to many other genes.

AUTHOR SUMMARY

After application of a gene transcription stimulus, in this case the hormone 17 β -estradiol, on large populations of cells over a short time period, we focused on quantifying and modeling the frequencies of GREB1 single allele activations. We have established an experimental and computational pipeline to analyze large numbers of high resolution smFISH images to detect and monitor active GREB1 alleles, that can be translatable to any target gene of interest. A key result is that, at the population level, activation of individual GREB1 alleles within the same nucleus do exhibit statistically significant dependencies which we quantify by the mutual information between activation states of pairs of alleles. After noticing that frequencies of joint alleles activations observed over our large cell populations evolve smoothly in time, we have defined a population level stochastic model which we fit to the observed time course of GREB1 activation frequencies. This provided coherent estimates of the mean time between rounds of GREB1 transcription and the mean lifetime of nascent mRNAs. Our algorithmic approach and experimental methods are applicable to many other genes.

Transcriptional bursting: stochasticity in deterministic development

The transcription of DNA by RNA polymerase occurs as a discontinuous process described as transcriptional bursting. This bursting behavior is observed across species and has been quantified using various stochastic modeling approaches. There is a large body of evidence that suggests the bursts are actively modulated by transcriptional machinery and play a role in regulating developmental processes. Under a commonly used two-state model of transcription, various enhancer-, promoter- and chromatin microenvironment-associated features are found to differentially influence the size and frequency of bursting events - key parameters of the two-state model. Advancement of modeling and analysis tools has revealed that the simple two-state model and associated parameters may not sufficiently characterize the complex relationship between these features. The majority of experimental and modeling findings support the view of bursting as an evolutionarily conserved transcriptional control feature rather than an unintended byproduct of the transcription process. Stochastic transcriptional patterns contribute to enhanced cellular fitness and execution of proper development programs, which posit this mode of transcription as an important feature in developmental gene regulation. In this Review, we present compelling examples of the role of transcriptional bursting in development and explore the question of how stochastic transcription leads to deterministic organism development.

Understanding spatiotemporal coupling of gene expression using single molecule RNA imaging technologies

Across all kingdoms of life, gene regulatory mechanisms underlie cellular adaptation to ever-changing environments. Regulation of gene expression adjusts protein synthesis and, in turn, cellular growth. Messenger RNAs are key molecules in the process of gene expression. Our ability to quantitatively measure mRNA expression in single cells has improved tremendously over the past decades. This revealed an unexpected coordination between the steps that control the life of an mRNA, from transcription to degradation. Here, we provide an overview of the state-of-the-art imaging approaches for measurement and quantitative understanding of gene expression, starting from the early visualizations of single genes by electron microscopy to current fluorescence-based approaches in single cells, including live-cell RNA-imaging approaches to FISH-based spatial transcriptomics across model organisms. We also highlight how these methods have shaped our current understanding of the spatiotemporal coupling between transcriptional and post-transcriptional events in prokaryotes. We conclude by discussing future challenges of this multidisciplinary field.Abbreviations: mRNA: messenger RNA; rRNA: ribosomal rDNA; tRNA: transfer RNA; sRNA: small RNA; FISH: fluorescence in situ hybridization; RNP: ribonucleoprotein; smFISH: single RNA molecule FISH; smiFISH: single molecule inexpensive FISH; HCR-FISH: Hybridization Chain-Reaction-FISH; RCA: Rolling Circle Amplification; seqFISH: Sequential FISH; MERFISH: Multiplexed error robust FISH; UTR: Untranslated region; RBP: RNA binding protein; FP: fluorescent protein; eGFP: enhanced GFP, MCP: MS2 coat protein; PCP: PP7 coat protein; MB: Molecular beacons; sgRNA: single guide RNA.

Tracking the Message: Applying Single Molecule Localization Microscopy to Cellular RNA Imaging

RNA function is increasingly appreciated to be more complex than merely communicating between DNA sequence and protein structure. RNA localization has emerged as a key contributor to the intricate roles RNA plays in the cell, and the link between dysregulated spatiotemporal localization and disease warrants an exploration beyond sequence and structure. However, the tools needed to visualize RNA with precise resolution are lacking in comparison to methods available for studying proteins. In the past decade, many techniques have been developed for imaging RNA, and in parallel super resolution and single-molecule techniques have enabled imaging of single molecules in cells. Of these methods, single molecule localization microscopy (SMLM) has shown significant promise for probing RNA localization. In this review, we highlight current approaches that allow super resolution imaging of specific RNA transcripts and summarize challenges and future opportunities for developing innovative RNA labeling methods that leverage the power of SMLM.

Enhanced single RNA imaging reveals dynamic gene expression in live animals

Imaging endogenous mRNAs in live animals is technically challenging. Here, we describe an MS2-based signal amplification with the Suntag system that enables live-cell RNA imaging of high temporal resolution and with 8xMS2 stem-loops, which overcomes the obstacle of inserting a 1300 nt 24xMS2 into the genome for the imaging of endogenous mRNAs. Using this tool, we were able to image the activation of gene expression and the dynamics of endogenous mRNAs in the epidermis of live C. elegans.

Folylpolyglutamate synthetase mRNA G-quadruplexes regulate its cell protrusion localization and enhance a cancer cell invasive phenotype upon folate repletion

BACKGROUND

Folates are crucial for the biosynthesis of nucleotides and amino acids, essential for cell proliferation and development. Folate deficiency induces DNA damage, developmental defects, and tumorigenicity. The obligatory enzyme folylpolyglutamate synthetase (FPGS) mediates intracellular folate retention via cytosolic and mitochondrial folate polyglutamylation. Our previous paper demonstrated the association of the cytosolic FPGS (cFPGS) with the cytoskeleton and various cell protrusion proteins. Based on these recent findings, the aim of the current study was to investigate the potential role of cFPGS at cell protrusions.

RESULTS

Here we uncovered a central role for two G-quadruplex (GQ) motifs in the 3'UTR of FPGS mediating the localization of cFPGS mRNA and protein at cell protrusions. Using the MBSV6-loop reporter system and fluorescence microscopy, we demonstrate that following folate deprivation, cFPGS mRNA is retained in the endoplasmic reticulum, whereas upon 15 min of folate repletion, this mRNA is rapidly translocated to cell protrusions in a 3'UTR- and actin-dependent manner. The actin dependency of this folate-induced mRNA translocation is shown by treatment with Latrunculin B and inhibitors of the Ras homolog family member A (RhoA) pathway. Upon folate repletion, the FPGS 3'UTR GQs induce an amoeboid/mesenchymal hybrid cell phenotype during migration and invasion through a collagen gel matrix. Targeted disruption of the 3'UTR GQ motifs by introducing point mutations or masking them by antisense oligonucleotides abrogated cell protrusion targeting of cFPGS mRNA.

CONCLUSIONS

Collectively, the GQ motifs within the 3'UTR of FPGS regulate its transcript and protein localization at cell protrusions in response to a folate cue, inducing cancer cell invasive phenotype. These novel findings suggest that the 3'UTR GQ motifs of FPGS constitute an attractive druggable target aimed at inhibition of cancer invasion and metastasis.

Dynamic Ins2 Gene Activity Defines β-Cell Maturity States

Transcriptional and functional cellular specialization has been described for insulin-secreting β-cells of the endocrine pancreas. However, it is not clear whether β-cell heterogeneity is stable or reflects dynamic cellular states. We investigated the temporal kinetics of endogenous insulin gene activity using live cell imaging, with complementary experiments using FACS and single-cell RNA sequencing, in β-cells from Ins2GFP knockin mice. In vivo staining and FACS analysis of islets from Ins2GFP mice confirmed that at a given moment, ∼25% of β-cells exhibited significantly higher activity at the evolutionarily conserved insulin gene, Ins2. Live cell imaging over days captured Ins2 gene activity dynamics in single β-cells. Autocorrelation analysis revealed a subset of oscillating cells, with mean oscillation periods of 17 h. Increased glucose concentrations stimulated more cells to oscillate and resulted in higher average Ins2 gene activity per cell. Single-cell RNA sequencing showed that Ins2(GFP)HIGH β-cells were enriched for markers of β-cell maturity. Ins2(GFP)HIGH β-cells were also significantly less viable at all glucose concentrations and in the context of endoplasmic reticulum stress. Collectively, our results demonstrate that the heterogeneity of insulin production, observed in mouse and human β-cells, can be accounted for by dynamic states of insulin gene activity.

Technologies Enabling Single-Molecule Super-Resolution Imaging of mRNA

The transient nature of RNA has rendered it one of the more difficult biological targets for imaging. This difficulty stems both from the physical properties of RNA as well as the temporal constraints associated therewith. These concerns are further complicated by the difficulty in imaging endogenous RNA within a cell that has been transfected with a target sequence. These concerns, combined with traditional concerns associated with super-resolution light microscopy has made the imaging of this critical target difficult. Recent advances have provided researchers the tools to image endogenous RNA in live cells at both the cellular and single-molecule level. Here, we review techniques used for labeling and imaging RNA with special emphases on various labeling methods and a virtual 3D super-resolution imaging technique.

Circ_CEA promotes the interaction between the p53 and cyclin-dependent kinases 1 as a scaffold to inhibit the apoptosis of gastric cancer

Circular RNAs (circRNAs) have been reported to play essential roles in tumorigenesis and progression. This study aimed to identify dysregulated circRNAs in gastric cancer (GC) and investigate the functions and underlying mechanism of these circRNAs in GC development. Here, we identify circ_CEA, a circRNA derived from the back-splicing of CEA cell adhesion molecule 5 (CEA) gene, as a novel oncogenic driver of GC. Circ_CEA is significantly upregulated in GC tissues and cell lines. Circ_CEA knockdown suppresses GC progression, and enhances stress-induced apoptosis in vitro and in vivo. Mechanistically, circ_CEA interacts with p53 and cyclin-dependent kinases 1 (CDK1) proteins. It serves as a scaffold to enhance the association between p53 and CDK1. As a result, circ_CEA promotes CDK1-mediated p53 phosphorylation at Ser315, then decreases p53 nuclear retention and suppresses its activity, leading to the downregulation of p53 target genes associated with apoptosis. These findings suggest that circ_CEA protects GC cells from stress-induced apoptosis, via acting as a protein scaffold and interacting with p53 and CDK1 proteins. Combinational therapy of targeting circ_CEA and chemo-drug caused more cell apoptosis, decreased tumor volume and alleviated side effect induced by chemo-drug. Therefore, targeting circ_CEA might present a novel treatment strategy for GC.

Research progress of live-cell RNA imaging techniques

RNA molecules play diverse roles in many physiological and pathological processes as they interact with various nucleic acids and proteins. The various biological processes of RNA are highly dynamic. Tracking RNA dynamics in living cells is crucial for a better understanding of the spatiotemporal control of gene expression and the regulatory roles of RNA. Genetically encoded RNA-tagging systems include MS2/MCP, PP7/PCP, boxB/λN22 and CRISPR-Cas. The MS2/MCP system is the most widely applied, and it has the advantages of stable binding and high signal-to-noise ratio, while the realization of RNA imaging requires gene editing of the target RNA, which may change the characteristics of the target RNA. Recently developed CRISPR-dCas13 system does not require RNA modification, but the uncertainty in CRISPR RNA (crRNA) efficiency and low signal-to-noise ratio are its limitations. Fluorescent dye-based RNA-tagging systems include molecular beacons and fluorophore-binding aptamers. The molecular beacons have high specificity and high signal-to-noise ratio; Mango and Peppers outperform the other RNA-tagging system in signal-to-noise, but they also need gene editing. Live-cell RNA imaging allows us to visualize critical steps of RNA activities, including transcription, splicing, transport, translation (for message RNA only) and subcellular localization. It will contribute to studying biological processes such as cell differentiation and the transcriptional regulation mechanism when cells adapt to the external environment, and it improves our understanding of the pathogenic mechanism of various diseases caused by abnormal RNA behavior and helps to find potential therapeutic targets. This review provides an overview of current progress of live-cell RNA imaging techniques and highlights their major strengths and limitations.

Fluorescence Microscopy-An Outline of Hardware, Biological Handling, and Fluorophore Considerations

Fluorescence microscopy has become a critical tool for researchers to understand biological processes at the cellular level. Micrographs from fixed and live-cell imaging procedures feature in a plethora of scientific articles for the field of cell biology, but the complexities of fluorescence microscopy as an imaging tool can sometimes be overlooked or misunderstood. This review seeks to cover the three fundamental considerations when designing fluorescence microscopy experiments: (1) hardware availability; (2) amenability of biological models to fluorescence microscopy; and (3) suitability of imaging agents for intended applications. This review will help equip the reader to make judicious decisions when designing fluorescence microscopy experiments that deliver high-resolution and informative images for cell biology.

Interrogating lncRNA functions via CRISPR/Cas systems

Long noncoding RNAs (lncRNAs) are an increasing focus of investigation due to their implications in diverse biological processes and disease. Nevertheless, the majority of lncRNAs are low in abundance and poorly conserved, posing challenges to functional studies. The CRISPR/Cas system, an innovative technology that has emerged over the last decade, can be utilized to further understand lncRNA function. The system targets specific DNA and/or RNA sequences via a guide RNA (gRNA) and Cas nuclease complex. We and others have utilized this technology in various applications such as lncRNA knockout, knockdown, overexpression, and imaging. In this review, we summarize how the CRISPR/Cas technology provides new tools to investigate the roles and therapeutic implications of lncRNAs.

Intracellular mRNA transport and localized translation

Fine-tuning cellular physiology in response to intracellular and environmental cues requires precise temporal and spatial control of gene expression. High-resolution imaging technologies to detect mRNAs and their translation state have revealed that all living organisms localize mRNAs in subcellular compartments and create translation hotspots, enabling cells to tune gene expression locally. Therefore, mRNA localization is a conserved and integral part of gene expression regulation from prokaryotic to eukaryotic cells. In this Review, we discuss the mechanisms of mRNA transport and local mRNA translation across the kingdoms of life and at organellar, subcellular and multicellular resolution. We also discuss the properties of messenger ribonucleoprotein and higher order RNA granules and how they may influence mRNA transport and local protein synthesis. Finally, we summarize the technological developments that allow us to study mRNA localization and local translation through the simultaneous detection of mRNAs and proteins in single cells, mRNA and nascent protein single-molecule imaging, and bulk RNA and protein detection methods.

Crystallin gene expression: Insights from studies of transcriptional bursting

Cellular differentiation is marked by temporally and spatially regulated gene expression. The ocular lens is one of the most powerful mammalian model system since it is composed from only two cell subtypes, called lens epithelial and fiber cells. Lens epithelial cells differentiate into fiber cells through a series of spatially and temporally orchestrated processes, including massive production of crystallins, cellular elongation and the coordinated degradation of nuclei and other organelles. Studies of transcriptional and posttranscriptional gene regulatory mechanisms in lens provide a wide range of opportunities to understand global molecular mechanisms of gene expression as steady-state levels of crystallin mRNAs reach very high levels comparable to globin genes in erythrocytes. Importantly, dysregulation of crystallin gene expression results in lens structural abnormalities and cataracts. The mRNA life cycle is comprised of multiple stages, including transcription, splicing, nuclear export into cytoplasm, stabilization, localization, translation and ultimate decay. In recent years, development of modern mRNA detection methods with single molecule and single cell resolution enabled transformative studies to visualize the mRNA life cycle to generate novel insights into the sequential regulatory mechanisms of gene expression during embryogenesis. This review is focused on recent major advancements in studies of transcriptional bursting in differentiating lens fiber cells, analysis of nascent mRNA expression from bi-directional promoters, transient nuclear accumulation of specific mRNAs, condensation of chromatin prior lens fiber cell denucleation, and outlines future studies to probe the interactions of individual mRNAs with specific RNA-binding proteins (RBPs) in the cytoplasm and regulation of translation and mRNA decay.

Advances in Confocal Microscopy and Selected Applications

Over the last 30 years, confocal microscopy has emerged as a primary tool for biological investigation across many disciplines. The simplicity of use and widespread accessibility of confocal microscopy ensure that it will have a prominent place in biological imaging for many years to come, even with the recent advances in light sheet and field synthesis microscopy. Since these more advanced technologies still require significant expertise to effectively implement and carry through to analysis, confocal microscopy-based approaches still remain the easiest way for biologists with minimal imaging experience to address fundamental questions about how their systems are arranged through space and time. In this review, we discuss a number of advanced applications of confocal microscopy for probing the spatiotemporal dynamics of biological systems.

Enabling high-throughput single-animal gene-expression studies with molecular and micro-scale technologies

Gene expression and regulation play diverse and important roles across all living systems. By quantifying the expression, whether in a sample of single cells, a specific tissue, or in a whole animal, one can gain insights into the underlying biology. Many biological questions now require single-animal and tissue-specific resolution, such as why individuals, even within an isogenic population, have variations in development and aging across different tissues and organs. The popular techniques that quantify the transcriptome (e.g. RNA-sequencing) process populations of animals and cells together and thus, have limitations in both individual and spatial resolution. There are single-animal assays available (e.g. fluorescent reporters); however, they suffer other technical bottlenecks, such as a lack of robust sample-handling methods. Microfluidic technologies have demonstrated various improvements throughout the years, and it is likely they can enhance the impact of these single-animal gene-expression assays. In this perspective, we aim to highlight how the engineering/method-development field have unique opportunities to create new tools that can enable us to robustly answer the next set of important questions in biology that require high-density, high-quality gene expression data.

Visualization of Transiently Expressed mRNA in Plants Using MS2

RNA transport and localization are evolutionarily conserved processes that allow protein translation to occur at specific subcellular sites and thereby having fundamental roles in the determination of cell fates, embryonic patterning, asymmetric cell division, and cell polarity. In addition to localizing RNA molecules to specific subcellular sites, plants have the ability to exchange RNA molecules between cells through plasmodesmata (PD). Plant RNA viruses hijack the mechanisms of intracellular and intercellular RNA transport to establish localized replication centers within infected cells and then to disseminate their infectious genomes between cells and throughout the plant organism with the help of their movement proteins (MP). In this chapter, we describe the transient expression of the tobacco mosaic virus movement protein (TMV-MP) and the application of the MS2 system for the in vivo labeling of the MP-encoding mRNA. The MS2 method is based on the binding of the bacteriophage coat protein (CP) to its origin of assembly (OAS) in the phage RNA. Thus, to label a specific mRNA in vivo, a tandem repetition of a 19-nucleotide-long stem-loop (SL) sequence derived from the MS2 OAS sequence (MSL) is transcriptionally fused to the RNA under investigation. The RNA is detected by the co-expression of fluorescent protein-tagged MS2 CP (MCP), which binds to each of the MSL elements. In providing a detailed protocol for the in vivo visualization of TMV-MP mRNA tagged with the MS2 system in Nicotiana benthamiana epidermal cells, we describe (1) the specific DNA constructs, (2) Agrobacterium tumefaciens-mediated transfection for their transient expression in plants, and (3) imaging conditions required to obtain high-quality mRNA imaging data.