Biology subjects

Nakamura, S.

Publications and source records attributed to Nakamura, S..

At least 37 records · Page 2Linked to original sources

bioRxiv2025

Turbulence orchestrates actin-mitochondria dynamics to preserve GPIbα and support iPSC-derived platelet biogenesis

The in vitro manufacturing of induced pluripotent stem cell-derived platelets (iPSC-platelets) remains limited by low yield and poor quality, thus impeding practical clinical application. To address this, we developed a turbulence-assisted system using defined physical stimulation to enhance platelet production from immortalized megakaryocyte progenitor cell lines (imMKCLs). This approach significantly increases the yield of glycoprotein Ib (GPIb) functional iPSC-platelets. However, the underlying mechanisms remained unclear. Here, we reveal that GPIb iPSC-platelets retain high mitochondrial membrane potential, low phosphatidylserine (PS) exposure, and active ATP-dependent flippases, preserving mitochondrial integrity and platelet functionality. In contrast, GPIb- platelets exhibit PS exposure, ADAM17 activation, and selective GPIb shedding. Notably, turbulent flow induces late-stage actin depolymerization, promoting even mitochondrial distribution within maturing imMKCLs and enhancing mitochondrial inheritance to iPSC-platelets. These findings highlight the key role of turbulence in regulating actin dynamics and mitochondrial allocation during platelet biogenesis, providing a mechanistic foundation for improving in vitro platelet production for therapeutic use.

cell biology↗

bioRxiv2025

Spatial dynamics of the tumor microenvironment in emerging resistance to targeted therapy in EGFR-mutated NSCLC

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) provide therapeutic benefit in EGFR mutation-positive non-small cell lung cancer, but some individuals develop early resistance. We performed spatial transcriptomics analysis of pre- and posttreatment tumor samples from the same patients to explore the underlying mechanisms of such early resistance. The proportion and activation of fibroblasts increased in association with the development of early resistance, whereas a distinct tumor cell cluster showed activation of tumor necrosis factor- signaling via the NF-{kappa}B pathway even before treatment. Also in the early resistance sample, specific tumor cell clusters interacted with immune and stromal cells. Immature tertiary lymphoid structures (TLSs) were enriched in the early resistance sample, whereas mature TLSs were observed in the long-term response sample. These findings implicate tumor heterogeneity and an inflammatory tumor microenvironment in early EGFR-TKI resistance, providing insight into potential therapeutic strategies to improve treatment outcomes.

cancer biology↗

bioRxiv2024

High-resolution Cryo-EM visualises hydrated type I and IV pilus structures from enterotoxigenic Escherichia coli

To efficiently colonise intestinal epithelium, enteric pathogens utilise a wide variety of pilus filaments, including those synthesised by the chaperone-usher or type IV pilus assembly pathway. Despite the importance of these filaments as potential drug and vaccine targets, their large size and dynamic nature present challenges for atomic-resolution structural determination. Here, we used cryo-electron microscopy (cryo-EM) and whole genome sequencing to identify and determine the structures of type I and IV pili expressed in enterotoxigenic Escherichia coli. The well-defined cryo-EM maps at resolutions of 2.20 and 1.78 [A] for Type I and Type IV pilus, respectively, facilitated de novo structural modelling for these filaments, revealing side chain structures in detail. Further, we resolved thousands of hydrated water molecules around and within the inner core of the filaments, functioning as a buffer to stabilise the otherwise metastable subunit assembly. The high-resolution structures offer novel insights into the subunit-subunit interactions, providing important clues to understand pilus assembly, stability, and flexibility.

microbiology↗

bioRxiv2024

Identification of Ephrin type-B receptor 4 as a critical mediator of tissue fibrosis

Pulmonary fibrosis (PF) is a pathology associated with interstitial lung diseases (ILDs), including idiopathic pulmonary fibrosis (IPF). Fibrosis promotes continual secretion of extracellular matrix (ECM), producing non-functional scar tissue and causing organ failure. This study investigated the tyrosine kinase receptor Ephrin type-B receptor 4 (EphB4) as a mediator of PF. To this end, we generated mice with conditional Col1a2-driven deletion of Ephb4 and used a preclinical mouse model of PF, total and single nuclei RNA (snRNA) sequencing, NanoString, previously published single cell data, computational analysis, and functional assays of mouse and human healthy control and IPF lung fibroblasts. Col1a2-CreERT-driven Ephb4 deletion, or EphB4 inhibition via NVP-BHG712, markedly protected against bleomycin-induced PF. Total RNA-sequencing of fibroblasts isolated from Ephb4-deficient fibrotic mouse lungs exhibited reduced expression of ECM, ER Cargo, and protein trafficking-related genes. NVP-BHG712 reduced expression of these identified genes in mouse lung fibroblasts under fibrotic conditions in vitro. SnRNA sequencing of mouse lungs treated with NVP-BHG712 identified transcriptomic changes of ECM genes in specific fibroblast subpopulations. RNA sequencing, computational, and functional assays using mouse and human IPF fibroblasts identified elastin as a key mediator involved in EphB4 signaling. Combined, our data show that EphB4 is a crucial mediator of PF.

pathology↗

bioRxiv2024

Mouth-attaching copepod Salmincola markewitschi reduces the body condition and growth of juvenile salmonid Salvelinus leucomaenis by decreasing host feeding activity: evidence from parasite removal experiment

Ectoparasitic copepods in the genus Salmincola Wilson, 1915 are considered harmful to host salmonids, yet experimental studies on whether and how these copepods affect hosts are critically limited. We evaluated the effects of the mouth-attaching Salmincola markewitschi Shedko and Shedko, 2002 on juvenile white-spotted charr Salvelinus leucomaenis (Pallas, 1814) using a parasite removal experiment where all individuals were artificially infected, and then parasites were removed in one group (i.e., treatment), while the copepods were left in another group (i.e., control). We hypothesized that the copepods reduce host feeding, thereby reducing host body condition and growth. The alternative hypothesis is that parasites do not change host feeding, or even increase because of the compensation for the negative effect. In this case, host condition and growth would not be reduced. The control group (parasite remained) had lower food consumption, body condition, and growth compared to the treatment (parasite removed). Thus, S. markewitschi negatively affected hosts by reducing host feeding, and no behavioral compensation was observed. It remains unknown, however, whether reduced feeding was due to impaired swallowing or physiological stresses caused by infections. Further experiments on gill- and body-surface-attaching Salmincola species could provide deeper insights into how these parasites influence host health.

ecology↗

bioRxiv2024

Mechanosensing by Piezo1 regulates osteoclast differentiation via PP2A-Akt axis in periodontitis

Mechanical stimulus to the multicellular bone unit (MBU) plays a key role in normal bone remodeling, whereas disuse osteoporosis, for example, represents loss of bone owing to lack of mechanical stresses. The analogy can be applied to a variety of pathogenic bone lytic complications, including periodontitis, in which local mechanical stress appears to be diminished. The activation of mechanosensitive Piezo1 Ca2+ channel expressed by osteoblasts and osteocytes in the MBU elicits the osteogenic signals in those cells. However, since osteoclast (OC)-specific Piezo1-gene knockout mice showed no skeletal phenotype, it has been assumed that Piezo1 might not play any role in OC-mediated bone remodeling. Here, however, we showed that mechanical stimulation of Piezo1 expressed on preosteoclasts (pre-OCs) downmodulates OC formation and, hence, bone resorptive activity in periodontitis, accompanied by significantly reduced expression of NFATc1, a master transcription factor for RANKL-induced OC-genesis. We know that the Ca2+/calcineurin/NFAT axis upregulates NFATc1 activation in pre-OCs. Interestingly, Piezo1-elicited Ca2+ influx did not affect NFATc1 expression. Instead, PP2A-mediated dephosphorylation of Akt downregulated NFATc1 in Piezo1-activated pre-OCs. However, systemic administration with Yoda1, a Piezo1 chemical agonist, or local injection of PP2A agonist, significantly downregulated the bone resorption induced in a mouse model of periodontitis, together with reduced numbers of TRAP+/phospho-Akt+ pre-OCs in local bone. These results suggest that mechanosensing by Piezo1 expressed on pre-OCs can downmodulate the RANKL-induced OC-genesis via the PP2A/Akt-dephosphorylation pathway, but that such Piezo1-mediated downregulation of bone resorption is attenuated in periodontitis. Significance StatementThe mechanosensitive Ca2+ channel Piezo1 plays important regulatory roles in a variety of cellular activities. RANKL-mediated OC-genesis requires permissive co-stimulatory signal from ITAM receptors, such as OSCAR and TREM2, to trigger the calcineurin/calmodulin signaling axis via Ca2+ oscillation, thereby upregulating NFATc1 expression. Activation of Piezo1 remarkably suppressed RANKL-induced NFATc1 activation which, in turn, reduced OC-genesis. Such mechanical activation of Piezo1 expressed on pre-OCs induced intracellular Ca2+ influx. Nonetheless, PP2A-mediated dephosphorylation of Akt, not the calcineurin/calmodulin pathway, suppressed NFATc1 in RANKL-elicited OC-genesis and resultant bone resorption, both in vitro and in vivo. These results indicate that mechanostress applied to pre-OCs can downregulate pathogenic OC-genesis and that Piezo1, as the mediator, is a novel molecular target for the development of anti-osteolytic therapies.

cell biology↗

bioRxiv2024

Ancient genomics reveals a genetic continuum with dual structure in the Classic Copan

Copan was a major capital at the southeasternmost of the Maya civilization, serving as a crossroads connecting Central and South America. In 426/427 CE, the city witnessed the establishment of a royal dynasty, which endured for approximately 400 years. Despite extensive historical and archaeological records, there remains limited information regarding the genetic origins of people who resided in Copan. Here, we present seven Classic Copan genomes including an enigmatic dynastic ruler and his sacrificed companion. Our analysis identifies a high genetic affinity of the Classic Copan with present-day Maya. Both groups exhibit an admixture of Mesoamerican and South American Farmer (SAF) ancestry, with a shift in a dominant component from SAF to Mesoamerican. At the individual level, commoners show a more prominent SAF ancestry, while the royal individual demonstrates nearly equal contributions from two ancestors. These results highlight a dual ancestral structure in this geographic extreme of the Classic Maya state, uncovering a cline of Mesoamerican ancestry across individuals.

evolutionary biology↗

bioRxiv2024

The Rubicon-WIPI axis regulates exosome biogenesis during aging

Cells release intraluminal vesicles (ILVs) in multivesicular bodies as exosomes to communicate with other cells. Although recent studies suggest an intimate link between exosome biogenesis and autophagy, the detailed mechanism is not fully understood. Here we employed comprehensive RNAi screening for autophagy-related factors and discovered that Rubicon, a negative regulator of autophagy, is essential for exosome release. Rubicon recruits WIPI2d to endosomes to promote exosome biogenesis. Interactome analysis of WIPI2d identified the ESCRT components that are required for ILV formation. Notably, we found that Rubicon is required for an age-dependent increase of exosome release in mice. In addition, small RNA sequencing of serum exosomes revealed that Rubicon determines the fate of exosomal microRNAs associated with cellular senescence and longevity pathways. Taken together, our current results suggest that the Rubicon-WIPI axis functions as a key regulator of exosome biogenesis and is responsible for the age-dependent changes in exosome quantity and quality.

cell biology↗

bioRxiv2024

Effects of cognitive load and years of experience on phase-amplitude coupling in simultaneous interpretation

Simultaneous interpretation is a highly cognitively demanding task that requires constant attention switching between languages. Interest continues to grow in the contribution of phase-amplitude coupling (PAC), which involves the cooperative interaction of multiple oscillations and working memory. In this study, we established subjective definitions for cognitive load levels based on the subjective word familiarity of simultaneous interpretation, categorizing them as low, medium, or high. We then compared the changes in the PAC patterns between experienced interpreters and beginners. Experienced interpreters exhibited an increase in PAC, including theta-gamma PAC, which is linked to working memory, as well as theta-beta PAC, alpha-beta PAC and alpha-gamma PAC, with rising cognitive load levels in simultaneous interpreting. This suggests that experienced simultaneous interpreters choose a more adaptive neural processing strategy in response to the cognitive demands of interpretation language. In contrast, beginner interpreters do not show such changes in PACs, indicating either an underdeveloped or a different neurological approach to the cognitive load levels of interpretation language. The difference in PAC responses between the two groups reflects varying cognitive and interpretive strategies in the brain, where experienced interpreters might utilize more advanced neural mechanisms to manage higher levels of difficulty in simultaneous interpretation.

neuroscience↗

bioRxiv2024

The Role of Morphological Adaptability in Vibrio cholerae's Motility and Pathogenicity

Vibrio cholerae, the etiological agent of cholera, exhibits remarkable adaptability to different environmental conditions by undergoing morphological changes that significantly contribute to its pathogenicity and impact the epidemiology of the disease globally. This study investigates the morphological adaptability of the clinically isolated V. cholerae O1 strain, specifically focusing on the motility and pathogenicity differences between the filamentous and original comma-shaped forms within diverse viscosity conditions. Utilizing the El Tor strain of V. cholerae O1, we induced the transformation into the filamentous form and performed a comparative analysis with the canonical comma-shaped morphology. Our approach involved assessing motility patterns, swimming speeds, rotation rates, kinematics, and reversal frequencies through dark-field microscopy and high-speed imaging techniques. The findings reveal that filamentous V. cholerae cell retains enhanced motility in viscous environments. This suggests an evolutionary adaptation enabling survival across a range of habitats, notably the human gastrointestinal tract. Filamentous forms demonstrated increased reversal behavior at mucin interfaces, hinting at an advantage in penetrating the mucus layer. Rabbit intestinal loop assays further showed that both morphological forms exhibit similar fluid accumulation ratios, thus indicating comparable pathogenic potentials. These results underscore the significance of V. choleraes morphological flexibility in adapting to environmental viscosity changes, shedding light on the bacteriums intricate survival and infection strategies. Our study provides critical insights into the dynamics of cholera, underlining the importance of considering bacterial morphology in developing effective cholera control strategies.

microbiology↗

bioRxiv2023

Autophagosome development and chloroplast segmentation occur synchronously for piecemeal degradation of chloroplasts

Plants distribute many nutrients to chloroplasts during leaf development and maturation. When leaves senesce or experience sugar starvation, the autophagy machinery degrades chloroplast proteins to facilitate efficient nutrient reuse. Here, we report on the intracellular dynamics of an autophagy pathway responsible for piecemeal degradation of chloroplast components. Through live-cell monitoring of chloroplast morphology, we observed the formation of chloroplast budding structures in sugar-starved leaves. These buds were then released and incorporated into the vacuolar lumen as an autophagic cargo termed a Rubisco-containing body. The budding structures did not accumulate in mutants of core autophagy machinery, suggesting that autophagosome creation is required for forming chloroplast buds. Simultaneous tracking of chloroplast morphology and autophagosome development revealed that the isolation membranes of autophagosomes interact closely with part of the chloroplast surface before forming chloroplast buds. Chloroplasts then protrude at the site associated with the isolation membranes, which divide synchronously with autophagosome maturation. This autophagy-related division does not require DYNAMIN-RELATED PROTEIN 5B, which constitutes the division ring for chloroplast proliferation in growing leaves. An unidentified division machinery may thus fragment chloroplasts for degradation in coordination with the development of the chloroplast-associated isolation membrane.

plant biology↗

bioRxiv2023

Transcriptome Analysis Reveals Enhancement of Cardiogenesis-Related Signaling Pathways by S-nitroso-N-pivaloyl-D-penicillamine (SNPiP): Implications for Improved Diastolic Function and Cardiac Performance

We previously reported a novel compound called S-nitroso-N-pivaloyl-D-penicillamine (SNPiP), which was screened from a group of nitric oxide (NO) donor compounds with a basic chemical structure of S-nitroso-N-acetylpenicillamine (SNAP), to activate the non-neuronal acetylcholine (NNA) system. SNPiP-treated mice exhibited improved cardiac output and enhanced diastolic function, without an increase in heart rate. The NNA-activating effects included increased resilience to ischemia, modulation of energy metabolism preference, and activation of angiogenesis. Here, we performed transcriptome analysis of SNPiP-treated mice ventricles to elucidate how SNPiP exerts beneficial effects on cardiac function. A time-course study (24 and 48 h after SNPiP administration) revealed that SNPiP initially induced Wnt and cGMP-protein kinase G (PKG) signaling pathways, along with upregulation of genes involved in cardiac muscle tissue development and oxytocin signaling pathway. We also observed enrichment of glycolysis-related genes in SNPiP-treated samples, indicating a metabolic shift from oxidative phosphorylation to glycolysis following SNPiP administration in the hearts. Additionally, SNPiP significantly upregulated atrial natriuretic peptide (ANP) and sarcolipin (SLN), which play crucial roles in calcium handling and cardiac performance. These findings suggest that SNPiP may have therapeutic potential based on the pleiotropic mechanisms elucidated in this study.

molecular biology↗

bioRxiv2023

Machine-learning-based motion tracking revealed the inverse correlation between adhesivity and surface motility of the leptospirosis spirochete

Bacterial motility is generally a critical virulence factor for pathogenic species, and thus studies on bacterial motility are significant given that they elucidate the mechanisms of infection and disease. Although fluorescent labeling has been the mainstream approach to detecting individual bacteria in a population or in host tissues, it contains problems related to protein expression stability and interference with bacterial physiology. Here, we applied machine learning to microscopic image analysis to achieve label-free motion tracking of the zoonotic bacterium Leptospira interrogans on cultured animal cells. The label-free method allowed us to measure various leptospiral strains isolated from human and animal patients, and natural reservoirs, showing that fast mobility on kidney cells tends to result in severe symptom. We also analyzed the surface locomotion of mutant strains lacking outer membrane proteins (OMPs) and revealed that the loss of OMPs reduced adherence and facilitated motility on cultured kidney cells. The behavior of clinical isolates and OMP-deficient mutants on cultured cells showed the inverse correlation between adhesion and mobility, which could affect infection outcomes. Thus, our computer vision technique eliminated the restriction on available bacterial strains and provided information that could help in understanding the mechanisms underlying motility-dependent bacterial pathogenicity.

biophysics↗

bioRxiv2023

Mechanism Underlying the Immune Responses of a Sublingual Vaccine for SARS-CoV-2 with RBD Antigen and Adjuvant, Poly(I:C) or AddaS03, in Non-human Primates

A sublingual vaccine formulated with recombinant SARS-CoV-2 spike protein receptor binding domain (RBD) antigen and Poly(I:C)) adjuvant was assessed for its safety in non-human primates. This Poly(I:C)-adjuvanted sublingual vaccine was safe compared to the AddaS03-adjuvanted vaccine in blood tests and plasma CRP. The safety of the vaccine was also confirmed through quantitative reverse transcription PCR of six genes and ELISA of four cytokines associated with inflammation and related reactions. The Poly(I:C)- or AddaS03-adjuvanted sublingual vaccine produced RBD-specific IgA antibodies in nasal washings, saliva, and plasma. SARS-CoV-2 neutralizing antibodies were detected in plasma, suggesting that adjuvanted-sublingual vaccines protect against SARS-CoV-2 infection. "Yin and Yang"-like unique transcriptional regulation was observed through DNA microarray analyses of white blood cell RNAs from both vaccines, suppressing and enhancing immune responses and up- or downregulating genes associated with these immune responses. Poly(I:C) adjuvanted sublingual vaccination induced atypical up- or downregulation of genes related to immune suppression or tolerance; Treg differentiation; and T-cell exhaustion. Therefore, Poly(I:C) adjuvant is safe and favorable for sublingual vaccination and can induce a balanced "Yin/Yang" -like effect on immune responses.

immunology↗

bioRxiv2023

Genistein enhances NAD+ biosynthesis by binding to Prohibitin 1 and upregulating nicotinamide phosphoribosyltransferase in adipocytes

Decreased NAD+ levels in adipocytes cause adipose-tissue dysfunction, leading to systemic glucose and lipid metabolism failure. Therefore, developing small molecules and nutraceuticals that can increase NAD+ levels in adipocytes is necessary. Genistein, a nutraceutical derived from soybeans, has various physiological activities and improves glucose and lipid metabolism. In this study, we aimed to unravel the effects of genistein on the intracellular NAD+ levels in adipocytes and the underlying molecular mechanisms. We showed that genistein enhanced NAD+ biosynthesis by increasing the expression of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in NAD+ biosynthesis. A pull-down assay using genistein-immobilized beads identified prohibitin 1 (PHB1) as a target protein of genistein. The knockdown of PHB1 suppressed the genistein-induced increase in NAMPT expression and NAD+ levels in adipocytes. Genistein-bound PHB1 contributed to the stabilization of the transcription factor CCAAT/enhancer-binding protein {beta} through activation of extracellular signal-regulated kinase, resulting in increased NAMPT expression at the transcriptional level. Genistein induced dephosphorylation of peroxisome proliferator-activated receptor at serine 273 and increased the insulin-sensitizing adipokine, adiponectin, in adipocytes, whereas the knockdown of NAMPT and PHB1 abolished these genistein-mediated effects. Our results proved the potential efficacy of nutraceuticals in promoting NAD+ levels and restoring metabolic function in adipocytes. Furthermore, we identified PHB1, localized to the plasma membrane, as a candidate target protein for increased expression of NAMPT in adipocytes. Overall, these findings will assist in developing NAD+ boosting strategies to alleviate the metabolic dysfunctions in adipose tissues. Significance StatementIncreasing NAD+ levels is an important preventive strategy for maintaining metabolic function. Here, we showed that genistein, a nutraceutical, which increases NAD+ levels in adipocytes, increased NAD+ biosynthesis by upregulating nicotinamide phosphoribosyltransferase (NAMPT), a rate-limiting enzyme in the NAD+ biosynthesis pathway. Our findings also showed that genistein increased NAMPT expression by binding to prohibitin 1 in the plasma membrane. Genistein-induced increase in NAD+ levels promoted adiponectin expression, an insulin-sensitizing adipokine, in adipocytes. This study provides evidence that nutraceuticals, such as genistein, are effective in enhancing NAD+ biosynthesis in adipocytes and that PHB1 is a candidate target protein for increased expression of NAMPT to maintain metabolic functions in adipose tissues.

biochemistry↗

bioRxiv2023

An efficient induction method for human spinal lower motor neurons and high-throughput image analysis at the single cell level

This study presents a newly developed method to rapidly and efficiently induce human spinal lower motor neurons (LMNs) from induced pluripotent stem cells (iPSCs) for elucidation of the amyotrophic lateral sclerosis (ALS) pathomechanism and drug screening. Previous methods had several limitations such as poor efficiency and low purity of LMN induction and labor intensiveness of the induction and evaluation procedures. Our new protocol achieved nearly 80% induction efficiency in only 2 weeks by combining a small molecule-based approach and transduction of transcription factors. To overcome cellular heterogeneity, we analyzed morphology and viability of iPSC-derived LMNs on a cell-by-cell basis using time-lapse microscopy and machine learning, thus establishing a highly accurate pathophysiological evaluation system. Our rapid, efficient, and simplified protocol and single cell-based evaluation method allow the conduct of large-scale analysis and drug screening using iPSC-derived motor neurons.

neuroscience↗

bioRxiv2023

Construction of Fosmid-based SARS-CoV-2 replicons for antiviral drug screening and replication analyses in biosafety level 2 facilities

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has necessitated the global development of countermeasures since its outbreak. However, current therapeutics and vaccines to stop the pandemic are insufficient and this is mainly because of the emergence of resistant variants, which requires the urgent development of new countermeasures, such as antiviral drugs. Replicons, self-replicating RNAs that do not produce virions, are a promising system for this purpose because they safely recreate viral replication, enabling antiviral screening in biosafety level (BSL)-2 facilities. We herein constructed three pCC2Fos-based RNA replicons lacking some open reading frames (ORF) of SARS-CoV-2: the {Delta}orf2-8, {Delta}orf2.4, and {Delta}orf2 replicons, and validated their replication in Huh-7 cells. The functionalities of the {Delta}orf2-8 and {Delta}orf2.4 replicons for antiviral drug screening were also confirmed. We conducted puromycin selection following the construction of the {Delta}orf2.4-puro replicon by inserting a puromycin-resistant gene into the {Delta}orf2.4 replicon. We observed the more sustained replication of the {Delta}orf2.4-puro replicon by puromycin pressure. The present results will contribute to the establishment of a safe and useful replicon system for analyzing SARS-CoV-2 replication mechanisms as well as the development of novel antiviral drugs in BSL-2 facilities.

microbiology↗

bioRxiv2023

Conserved cis-acting motifs and localization of transcripts and proteins of MFT2 in barley and rice

MFT is an important regulator of seed dormancy in flowering plants. A natural mutation in the A-box motif in the promoter of wheat (Triticum aestivum) MFT2 on chromosome 3A (TaMFT2-3A) has been used to prevent pre-harvest sprouting (PHS) in wheat cultivars in East Asia. Previous research using in situ hybridization showed that TaMFT2-3A is primarily expressed in the seed scutellum. In this study, we analyzed the localization of transcripts and encoded proteins for the TaMFT2 homologs from barley (Hordeum vulgare) and rice (Oryza sativa), HvMFT2 and OsMFT2, respectively. RNA in situ hybridization showed that, like the wheat genes, the rice and barley homologs are primarily expressed in the scutellum, indicating that these three MFT2 genes have a common expression pattern during seed development. Analysis of the cis-acting regulatory elements of their promoter sequences showed that the three MFT2 promoters share eight seed-specific cis-acting RY motifs, which are binding sites for B3-domain transcription factors of the AFL-B3 and VIVIPAROUS1/ABI3-LIKE (VAL) families. In addition, we detected tandemly repeated and partially overlapping A-box motifs in the promoters of HvMFT2, TaMFT2-3B, and TaMFT2-3D, possibly explaining why the natural allele of TaMFT2-3A has been employed in breeding. We generated transgenic rice plants expressing nuclear-localized green fluorescent protein (NLS-2xGFP) and OsMFT2-GFP under the control of a 3-kb fragment of the OsMFT2 promoter. Immunohistochemical staining using anti-GFP antibodies mainly detected GFP in the scutellum and scutellar epithelium, which is an important tissue for initiating germination upon seed hydration. We confirmed these results by confocal microscopy of GFP fluorescence in seeds. Our results suggest that MFT2 expression in rice, barley, and wheat might be regulated by a similar network of transcription factors through multi-RY motifs in the MFT2 promoters, with possible roles in scutellar epithelium development.

plant biology↗