N-aryl pyrido cyanine derivatives are nuclear and organelle DNA markers for two-photon and super-resolution imaging

A Bright Red Molecular Marker for Super-Resolution Imaging of DNA Nanoscale Organization in Cells

SEZ-NDEA, a long-range emissive molecular marker, can be used in fluorescence microscopy for super-resolution imaging (SRRF) of DNA nanoscale organization in cells. The developed probe stains the cell nucleus with minimum cytoplasmic leakage with good contrast. It showed good photostability in cellular medium.

Visualizing DNA/RNA, Proteins, and Small Molecule Metabolites within Live Cells

Live cell imaging is essential for obtaining spatial and temporal insights into dynamic molecular events within heterogeneous individual cells, in situ intracellular networks, and in vivo organisms. Molecular tracking in live cells is also a critical and general requirement for studying dynamic physiological processes in cell biology, cancer, developmental biology, and neuroscience. Alongside this context, this review provides a comprehensive overview of recent research progress in live-cell imaging of RNAs, DNAs, proteins, and small-molecule metabolites, as well as their applications in molecular diagnosis, immunodiagnosis, and biochemical diagnosis. A series of advanced live-cell imaging techniques have been introduced and summarized, including high-precision live-cell imaging, high-resolution imaging, low-abundance imaging, multidimensional imaging, multipath imaging, rapid imaging, and computationally driven live-cell imaging methods, all of which offer valuable insights for disease prevention, diagnosis, and treatment. This review article also addresses the current challenges, potential solutions, and future development prospects in this field.

Compact lens-free imager using a thin-film transistor for long-term quantitative monitoring of stem cell culture and cardiomyocyte production

With advancements in human induced pluripotent stem cell (hiPSC) technology, there is an increasing demand for quality control techniques to manage the long-term process of target cell production effectively. While monitoring systems designed for use within incubators are promising for assessing culture quality, existing systems still face challenges in terms of compactness, throughput, and available metrics. To address these limitations, we have developed a compact and high-throughput lens-free imaging device named INSPCTOR. The device is as small as a standard culture plate, which allows for the installation of multiple units within an incubator. INSPCTOR utilises a large thin-film transistor image sensor, enabling simultaneous observation of six independent culture environments, each approximately 1 cm2. With this device, we successfully monitored the confluency of hiPSC cultures and identified the onset timing of epithelial-to-mesenchymal transition during mesodermal induction. Additionally, we quantified the beating frequency and conduction of hiPSC-derived cardiomyocytes by using high-speed imaging modes. This enabled us to identify the onset of spontaneous beating during differentiation and assess chronotropic responses in drug evaluations. Moreover, by tracking beating frequency over 10 days of cardiomyocyte maturation, we identified week-scale and daily-scale fluctuations, the latter of which correlated with cellular metabolic activity. The metrics derived from this device would enhance the reproducibility and quality of target cell production.

Next-generation red ultra-bright fluorescent dyes for nuclear imaging and peripheral blood leukocytes sorting

The nucleus is a membrane-bound organelle in eukaryotic cells and plays a crucial role in cellular processes. Visualizing nuclear morphology is essential for investigating nuclear functions and understanding the relationship between nuclear morphological alterations and multiple diseases. Fluorescent dyes have been developed to visualize nuclear morphology, but the selection of red nuclear-labeling fluorescent dyes remains limited (high price, unknown structure, or high toxicity). Herein, we have developed a red ultra-bright nuclear-targeted dye, BPC1, through the engineering of unsymmetrical cyanine dyes derived from D-π-A systems. BPC1 exhibits ultrahigh fluorescence brightness and exceptional cell permeability, and selectively stains nuclear DNA rather than mitochondrial DNA, enabling the visualization of the nucleus in diverse cells at extremely low doses (100 nM) and laser power (0.8 μW). Furthermore, BPC1 is utilized for nuclear staining in blood cells, aiding in the distinct visualization of the white blood cell nucleus and facilitating the identification and enumeration of various leukocyte types. Our study implies considerable commercial potential for BPC1 and underscores its capacity to serve as a powerful tool in life sciences and cell biology research.

Binder-Responsive DNA Strand Displacement Enables High-Throughput and High-Fidelity Discovering of Small Molecular DNA Binders

High-throughput screening (HTS) is pivotal in the discovery of small molecules that bind to DNA, yet there are limited sensing mechanisms available for designing HTS assays for DNA binders. Herein, we introduce a binder-responsive toehold-mediated DNA strand displacement (BR-TMSD) technique featuring programmable reaction kinetics in response to DNA-binder interactions. When two DNA binders are used, BR-TMSD is initiated through a rapid binder displacement, followed by the DNA strand displacement. The orthogonal displacement reactions of BR-TMSD enables a high-fidelity, dual-channel HTS assay, returning 19 new DNA binders from a library of 1,170 compounds.

Poaceae plants transfer cyclobutane pyrimidine dimer photolyase to chloroplasts for ultraviolet-B resistance

Photoreactivation enzyme that repairs cyclobutane pyrimidine dimer (CPD) induced by ultraviolet-B radiation, commonly called CPD photolyase (PHR) is essential for plants living under sunlight. Rice (Oryza sativa) PHR (OsPHR) is a unique triple-targeting protein. The signal sequences required for its translocation to the nucleus or mitochondria are located in the C-terminal region but have yet to be identified for chloroplasts. Here, we identified sequences located in the N-terminal region, including the serine-phosphorylation site at position 7 of OsPHR, and found that OsPHR is transported/localized to chloroplasts via a vesicle transport system under the control of serine-phosphorylation. However, the sequence identified in this study is only conserved in some Poaceae species, and in many other plants, PHR is not localized to the chloroplasts. Therefore, we reasoned that Poaceae species need the ability to repair CPD in the chloroplast genome to survive under sunlight and have uniquely acquired this mechanism for PHR chloroplast translocation.

Xanthene, cyanine, oxazine and BODIPY: the four pillars of the fluorophore empire for super-resolution bioimaging

In the realm of biological research, the invention of super-resolution microscopy (SRM) has enabled the visualization of ultrafine sub-cellular structures and their functions in live cells at the nano-scale level, beyond the diffraction limit, which has opened up a new window for advanced biomedical studies to unravel the complex unknown details of physiological disorders at the sub-cellular level with unprecedented resolution and clarity. However, most of the SRM techniques are highly reliant on the personalized special photophysical features of the fluorophores. In recent times, there has been an unprecedented surge in the development of robust new fluorophore systems with personalized features for various super-resolution imaging techniques. To date, xanthene, cyanine, oxazine and BODIPY cores have been authoritatively utilized as the basic fluorophore units in most of the small-molecule-based organic fluorescent probe designing strategies for SRM owing to their excellent photophysical characteristics and easy synthetic acquiescence. Since the future of next-generation SRM studies will be decided by the availability of advanced fluorescent probes and these four fluorescent building blocks will play an important role in progressive new fluorophore design, there is an urgent need to review the recent advancements in designing fluorophores for different SRM methods based on these fluorescent dye cores. This review article not only includes a comprehensive discussion about the recent developments in designing fluorescent probes for various SRM techniques based on these four important fluorophore building blocks with special emphasis on their effective integration into live cell super-resolution bio-imaging applications but also critically evaluates the background of each of the fluorescent dye cores to highlight their merits and demerits towards developing newer fluorescent probes for SRM.

A Small Compound, HYGIC, Promotes Hypocotyl Growth Through Ectopic Ethylene Response

Plant seedlings adjust the growth of the hypocotyl in response to surrounding environmental changes. Genetic studies have revealed key players and pathways in hypocotyl growth, such as phytohormones and light signaling. However, because of genetic redundancy in the genome, it is expected that not-yet-revealed mechanisms can be elucidated through approaches different from genetic ones. Here, we identified a small compound, HYGIC (HG), that simultaneously induces hypocotyl elongation and thickening, accompanied by increased nuclear size and enlargement of cortex cells. HG-induced hypocotyl growth required the ethylene signaling pathway activated by endogenous ethylene, involving CONSTITUTIVE PHOTOMORPHOGENIC 1, ETHYLENE INSENSITIVE 2 (EIN2) and redundant transcription factors for ethylene responses, ETHYLENE INSENSITIVE 3 (EIN3) and EIN3 LIKE 1. By using EBS:GUS, a transcriptional reporter of ethylene responses based on an EIN3-binding-cis-element, we found that HG treatment ectopically activates ethylene responses at the epidermis and cortex of the hypocotyl. RNA-seq and subsequent gene ontology analysis revealed that a significant number of HG-induced genes are related to responses to hypoxia. Indeed, submergence, a representative environment where the hypoxia response is induced in nature, promoted ethylene-signaling-dependent hypocotyl elongation and thickening accompanied by ethylene responses at the epidermis and cortex, which resembled the HG treatment. Collectively, the identification and analysis of HG revealed that ectopic responsiveness to ethylene promotes hypocotyl growth, and this mechanism is activated under submergence.

Meeting report: Third Franco-Japanese developmental biology meeting "New Frontiers in developmental biology: Celebrating the diversity of life"

The French and Japanese Developmental Biology Societies, teaming up with Human Frontier Science Program, were eager to meet back in person in November 2022 in the lovely city of Strasbourg. Top scientists in the developmental biology field from France and Japan, but also from United States, United Kingdom, Switzerland or Germany shared their exciting science during the 4 days of this meeting. Core fields of developmental biology such as morphogenesis, patterning, cell identity, and cell state transition, notably at the single cell level, were well represented, and a diversity of experimental models, including plants, animals, and other exotic organisms, as well as some in vitro cellular models, were covered. This event also extended the scope of classic scientific gatherings for two reasons. First the involvement of artists during the preparation of the event and on site. Second, part of the meeting was open for the general public through a series of outreach events, including a music and video presentation through projection mapping at Rohan palace, as well as public lectures.

Enabling programmable dynamic DNA chemistry using small-molecule DNA binders

The binding of small molecules to the double helical structure of DNA, through either intercalation or minor groove binding, may significantly alter the stability and functionality of DNA, which is a fundamental basis for many therapeutic and sensing applications. Here, we report that small-molecule DNA binders can also be used to program reaction pathways of a dynamic DNA reaction, where DNA strand displacement can be tuned quantitatively according to the affinity, charge, and concentrations of a given DNA binder. The binder-induced nucleic acid strand displacement (BIND) thus enables innovative technologies to accelerate the discovery and characterization of bioactive small molecules. Specifically, we demonstrate the comprehensive characterization of existing and newly discovered DNA binders, where critical parameters for binding affinity and sequence selectivity can be obtained in a single, unbiased molecular platform without the need for any specialized equipment. We also engineer a tandem BIND system as a high-throughput screening assay for discovering DNA binders, through which 8 DNA binders were successfully discovered from a library of 700 compounds.

Recent Development of Advanced Fluorescent Molecular Probes for Organelle-Targeted Cell Imaging

Fluorescent molecular probes are very powerful tools that have been generally applied in cell imaging in the research fields of biology, pathology, pharmacology, biochemistry, and medical science. In the last couple of decades, numerous molecular probes endowed with high specificity to particular organelles have been designed to illustrate intracellular images in more detail at the subcellular level. Nowadays, the development of cell biology has enabled the investigation process to go deeply into cells, even at the molecular level. Therefore, probes that can sketch a particular organelle's location while responding to certain parameters to evaluate intracellular bioprocesses are under urgent demand. It is significant to understand the basic ideas of organelle properties, as well as the vital substances related to each unique organelle, for the design of probes with high specificity and efficiency. In this review, we summarize representative multifunctional fluorescent molecular probes developed in the last decade. We focus on probes that can specially target nuclei, mitochondria, endoplasmic reticulums, and lysosomes. In each section, we first briefly introduce the significance and properties of different organelles. We then discuss how probes are designed to make them highly organelle-specific. Finally, we also consider how probes are constructed to endow them with additional functions to recognize particular physical/chemical signals of targeted organelles. Moreover, a perspective on the challenges in future applications of highly specific molecular probes in cell imaging is also proposed. We hope that this review can provide researchers with additional conceptual information about developing probes for cell imaging, assisting scientists interested in molecular biology, cell biology, and biochemistry to accelerate their scientific studies.

Small-molecule fluorogenic probes for mitochondrial nanoscale imaging

Mitochondria are inextricably linked to the development of diseases and cell metabolism disorders. Super-resolution imaging (SRI) is crucial in enhancing our understanding of mitochondrial ultrafine structures and functions. In addition to high-precision instruments, super-resolution microscopy relies heavily on fluorescent materials with unique photophysical properties. Small-molecule fluorogenic probes (SMFPs) have excellent properties that make them ideal for mitochondrial SRI. This paper summarizes recent advances in the field of SMFPs, with a focus on the chemical and spectroscopic properties required for mitochondrial SRI. Finally, we discuss future challenges in this field, including the design principles of SMFPs and nanoscopic techniques.

Small Fluorogenic Amino Acids for Peptide-Guided Background-Free Imaging

The multiple applications of super-resolution microscopy have prompted the need for minimally invasive labeling strategies for peptide-guided fluorescence imaging. Many fluorescent reporters display limitations (e.g., large and charged scaffolds, non-specific binding) as building blocks for the construction of fluorogenic peptides. Herein we have built a library of benzodiazole amino acids and systematically examined them as reporters for background-free fluorescence microscopy. We have identified amine-derivatized benzoselenadiazoles as scalable and photostable amino acids for the straightforward solid-phase synthesis of fluorescent peptides. Benzodiazole amino acids retain the binding capabilities of bioactive peptides and display excellent signal-to-background ratios. Furthermore, we have demonstrated their application in peptide-PAINT imaging of postsynaptic density protein-95 nanoclusters in the synaptosomes from mouse brain tissues.

Small Fluorogenic Amino Acids for Peptide-Guided Background-Free Imaging

The multiple applications of super-resolution microscopy have prompted the need for minimally invasive labeling strategies for peptide-guided fluorescence imaging. Many fluorescent reporters display limitations (e.g., large and charged scaffolds, non-specific binding) as building blocks for the construction of fluorogenic peptides. Herein we have built a library of benzodiazole amino acids and systematically examined them as reporters for background-free fluorescence microscopy. We have identified amine-derivatized benzoselenadiazoles as scalable and photostable amino acids for the straightforward solid-phase synthesis of fluorescent peptides. Benzodiazole amino acids retain the binding capabilities of bioactive peptides and display excellent signal-to-background ratios. Furthermore, we have demonstrated their application in peptide-PAINT imaging of postsynaptic density protein-95 nanoclusters in the synaptosomes from mouse brain tissues.

Spin-Orbit Coupling Calculation Combined with the Reference Interaction Site Model Self-Consistent Field Explicitly Including Constrained Spatial Electron Density Distribution

Studying the radiative and non-radiative decay processes of molecules in a solution is an important issue in the design of organic and functional molecules. Theoretical approaches have great potential for revealing this decay process through computation of various parameters, such as the energy surfaces at the excited state and spin-orbit coupling (SOC). The development of quantum chemical programs has enabled the calculation of SOC values to become popular for the gas phase. However, SOC calculations in solution have some difficulties that need to be overcome. In the present study, the authors combined the SOC calculations with the reference interaction site model self-consistent field explicitly including constrained spatial electron density distribution. To validate the reliability of our method, the decay process of dimethylaminobenzonitrile in cyclohexane and acetonitrile was studied. By computing the SOC values in both solution systems, the authors were able to investigate the decay process at the atomistic level. Furthermore, a natural transition orbital analysis and the measurement of the decomposed SOC values were found to provide a clear understanding of intersystem crossing.

Dynamics of mitochondrial distribution during development and asymmetric division of rice zygotes

Mitochondria change their distribution from nuclear peripheral to uniformly distributed in cytoplasm during zygotic development of rice, and the mitochondria re-distribute around nucleus for even segregation into daughter cells. Mitochondria are highly dynamic organelles that actively move and change their localization along with actin filaments during the cell cycle. Studies of mitochondrial dynamics and distribution in plant cells have mainly been conducted on somatic cells, and our understanding about these aspects during the formation and development of zygotes remains limited. In this study, mitochondrial nucleoids of rice egg cells and zygotes were successfully stained by using N-aryl pyrido cyanine 3 (PC3), and their intracellular localization and distribution were demonstrated. Mitochondria in rice egg cells were small and coccoid in shape and were primarily distributed around the nucleus. Upon gamete fusion, the resulting zygotes showed mitochondrial dispersion and accumulation equivalent to those in rice egg cells until 8 h after fusion (HAF). Around 12 HAF, the mitochondria started to disperse throughout the cytoplasm of the zygotes, and this dispersive distribution pattern continued until the zygotes entered the mitotic phase. At early prophase, the mitochondria redistributed from dispersive to densely accumulated around the nucleus, and during the metaphase and anaphase, the mitochondria were depleted from possible mitotic spindle region. Thereafter, during cell plate formation between daughter nuclei, the mitochondria distributed along the phragmoplast, where the new cell wall was formed. Finally, relatively equivalent amounts of mitochondria were detected in the apical and basal cells which were produced through asymmetric division of the zygotes. Further observation by treating the egg cell with latrunculin B revealed that the accumulation of mitochondria around the nuclear periphery in egg cells and early zygotes depended on the actin meshwork converging toward the egg or zygote nucleus.

Development of 1,8-naphthalimide dyes for rapid imaging of subcellular compartments in plants

Here, we report the installation of 1,8-naphthalimide dyes in live cell imaging of plants. We developed a series of 1,8-naphthalimide-based probes that illuminate different subcellular compartments by altering their spectral characteristics. Simple infiltration of the probes into leaves rapidly visualized the structure of chloroplasts or the vacuole. We further demonstrated that these probes are applicable to monitor the organelle behaviors in an autophagy pathway.

Revealing the Dynamics of Mitochondrial Microenvironment during Apoptosis under Two-photon Fluorescence Lifetime Microscopy by a Cyclic Iridium (III) Complex

Mitochondria-mediated apoptosis is a major mode of cell death and is inextricably linked to various pathological processes such as tumorigenesis. However, there is still a paucity of non-toxic tools that...

Advances in Synthetic Fluorescent Probe Labeling for Live-Cell Imaging in Plants

Fluorescent probes are powerful tools for visualizing cellular and subcellular structures, their dynamics and cellular molecules in living cells and enable us to monitor cellular processes in a spatiotemporal manner within complex and crowded systems. In addition to popular fluorescent proteins, a wide variety of small-molecule dyes have been synthesized through close association with the interdisciplinary field of chemistry and biology, ranging from those suitable for labeling cellular compartments such as organelles to those for labeling intracellular biochemical and biophysical processes and signaling. In recent years, self-labeling technologies including the SNAP-tag system have allowed us to attach these dyes to cellular domains or specific proteins and are beginning to be employed in plant studies. In this mini review, we will discuss the current range of synthetic fluorescent probes that have been exploited for live-cell imaging and the recent advances in the application that enable genetical tagging of synthetic probes in plant research.

Progress on the Physiological Function of Mitochondrial DNA and Its Specific Detection and Therapy

Mitochondrial DNA (mtDNA) is the genetic information of mitochondrion, and its structure is circular double-stranded. Despite the diminutive size of the mitochondrial genome, mtDNA mutations are an important cause of mitochondrial diseases which are characterized by defects in oxidative phosphorylation (OXPHOS). Mitochondrial diseases are involved in multiple systems, particularly in the organs that are highly dependent on aerobic metabolism. The diagnosis of mitochondrial disease is more complicated since mtDNA mutations can cause various clinical symptoms. To realize more accurate diagnosis and treatment of mitochondrial diseases, the detection of mtDNA and the design of drugs acting on it are extremely important. Over the past few years, many probes and therapeutic drugs targeting mtDNA have been developed, making significant contributions to fundamental research including elucidation of the mechanisms of mitochondrial diseases at the genetic level. In this review, we summarize the structure, function, and detection approaches for mtDNA. The most current topics in this field, such as mechanistic exploration and treatment of mtDNA mutation-related disorders, are also reviewed. Specific attention is given to discussing the design and development of these probes and drugs for mtDNA. We hope that this review will provide readers with a comprehensive understanding of the importance of mtDNA, and promote the development of effective molecules for theragnosis of mtDNA mutation-related diseases.

Metal-Nano-Ink Coating for Monitoring and Quantification of Cotyledon Epidermal Cell Morphogenesis

During cotyledon growth, the pavement cells, which make up most of the epidermal layer, undergo dynamic morphological changes from simple to jigsaw puzzle-like shapes in most dicotyledonous plants. Morphological analysis of cell shapes generally involves the segmentation of cells from input images followed by the extraction of shape descriptors that can be used to assess cell shape. Traditionally, replica and fluorescent labeling methods have been used for time-lapse observation of cotyledon epidermal cell morphogenesis, but these methods require expensive microscopes and can be technically demanding. Here, we propose a silver-nano-ink coating method for time-lapse imaging and quantification of morphological changes in the epidermal cells of growing Arabidopsis thaliana cotyledons. To obtain high-resolution and wide-area cotyledon surface images, we placed the seedlings on a biaxial goniometer and adjusted the cotyledons, which were coated by dropping silver ink onto them, to be as horizontal to the focal plane as possible. The omnifocal images that had the most epidermal cell shapes in the observation area were taken at multiple points to cover the whole surface area of the cotyledon. The multi-point omnifocal images were automatically stitched, and the epidermal cells were automatically and accurately segmented by machine learning. Quantification of cell morphological features based on the segmented images demonstrated that the proposed method could quantitatively evaluate jigsaw puzzle-shaped cell growth and morphogenesis. The method was successfully applied to phenotyping of the bpp125 triple mutant, which has defective pavement cell morphogenesis. The proposed method will be useful for time-lapse non-destructive phenotyping of plant surface structures and is easier to use than the conversional methods that require fluorescent dye labeling or transformation with marker gene constructs and expensive microscopes such as the confocal laser microscope.