Publications by authors named "Hiroyuki Kasahara"

Cellular auxin (indole-3-acetic acid, IAA) levels are coordinately regulated by IAA biosynthesis and inactivation. IAA is synthesized through sequential reactions by two enzymes, TAA1 and YUCCA, in a linear indole-3-pyruvic acid (IPA) pathway. TAA1 converts tryptophan to IPA, and YUCCA catalyzes the oxidative decarboxylation of IPA into IAA.

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Several plant-associated microbes synthesize the auxinic plant growth regulator phenylacetic acid (PAA) in culture; however, the role of PAA in plant-pathogen interactions is not well understood. In this study, we investigated the role of PAA during interactions between the phytopathogenic bacterium strain DC3000 (DC3000) and the model plant host, . Previous work demonstrated that indole-3-acetaldehyde dehydrogenase A (AldA) of DC3000 converts indole-3-acetaldehyde (IAAld) to the auxin indole-3-acetic acid (IAA).

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Aim: Oral function in patients with schizophrenia has not been well-characterized. To address this, we performed a cross-sectional study of oral function in Japanese inpatients with schizophrenia.

Methods: We measured oral function, including occlusal force, tongue-lip motor function, tongue pressure, and masticatory function in 130 Japanese inpatients with schizophrenia.

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Plants adopt optimal tolerance strategies depending on the intensity and duration of stress. Retaining water is a priority under short-term drought conditions, whereas maintaining growth and reproduction processes takes precedence over survival under conditions of prolonged drought. However, the mechanism underlying changes in the stress response depending on the degree of drought is unclear.

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Background: In the Diagnostic and Statistical Manual and Mental Disorders, Fifth Edition (DSM-5), autism spectrum disorder (ASD) and social (pragmatic) communication disorder (SCD) were described as a new category of psychiatry nosography. SCD involves impairments in social communication and social interaction but not restricted, repetitive patterns of behavior, interests, or activities. The autism spectrum quotient (AQ) was developed to screen for autism tendencies in adults with normal intelligence.

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Article Synopsis
  • Lateral root (LR) formation is crucial for root system development in vascular plants, and mutations in the GNOM gene disrupt this process in Arabidopsis thaliana by affecting auxin response.
  • A mutation identified as fewer roots suppressor1 (fsp1) partially restores LR formation in GNOM mutants, linked to a gene named SUPERROOT2 (SUR2), which regulates the biosynthesis of auxin and indole glucosinolate.
  • The fsp1 mutation elevates local auxin levels and stabilizes sites of auxin accumulation in roots, indicating SUR2's role in LR founder cell formation and the interplay between SUR2 and GNOM for LR initiation.
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Purpose: There is little evidence regarding the effects of dental status on body mass index (BMI) in inpatients with schizophrenia. Thus, we performed a cross-sectional study to explore the associations between the number of remaining teeth and BMI in Japanese inpatients with schizophrenia.

Patients And Methods: We performed multiple regression analysis to assess the effects of potential predictors (age, sex, number of remaining teeth, number of antipsychotics prescribed, chlorpromazine equivalent dose, and antipsychotic type) on BMI in 212 inpatients with schizophrenia.

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The phytohormone auxin, indole-3-acetic acid (IAA), plays a prominent role in plant development. Auxin homeostasis is coordinately regulated by auxin synthesis, transport, and inactivation; however, the physiological contribution of auxin inactivation to auxin homeostasis has not been determined. The GH3 IAA-amino acid conjugating enzymes play a central role in auxin inactivation.

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In two-step culture systems for efficient shoot regeneration, explants are first cultured on auxin-rich callus-inducing medium (CIM), where cells are activated to proliferate and form calli containing root-apical meristem (RAM)-type stem cells and stem cell niche, and then cultured on cytokinin-rich shoot-inducing medium (SIM), where stem cells and stem cell niche of the shoot apical meristem (SAM) are established eventually leading to shoot regeneration. In the present study, we examined the effects of inhibitors of auxin biosynthesis and polar transport in the two-step shoot regeneration culture of Arabidopsis and found that, when they were applied during CIM culture, although callus growth was repressed, shoot regeneration in the subsequent SIM culture was significantly increased. The regeneration-stimulating effect of the auxin biosynthesis inhibitor was not linked with the reduction in the endogenous indole-3-acetic acid (IAA) level.

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4-Phenylbutyric acid (4PBA) is utilized as a drug to treat urea cycle disorders and is also being studied as a potential anticancer drug that acts via its histone deacetylase (HDAC) inhibitor activity. During a search to find small molecules that affect plant regeneration in Arabidopsis, we found that 4PBA treatment promotes this process by mimicking the effect of exogenous auxin. Specifically, plant tissue culture experiments revealed that a medium containing 4PBA enhances callus formation and subsequent shoot regeneration.

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Gretchen Hagen 3 (GH3) amido synthetases conjugate amino acids to a carboxyl group of small molecules including hormones auxin, jasmonate, and salicylic acid. The Arabidopsis genome harbors 19 GH3 genes, whose exact roles in plant development have been difficult to define because of genetic redundancy among the GH3 genes. Here we use CRISPR/Cas9 gene editing technology to delete the Arabidopsis group II GH3 genes, which are able to conjugate indole-3-acetic acid (IAA) to amino acids.

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Article Synopsis
  • This study reveals the main pathway for inactivating the plant hormone auxin, specifically indole-3-acetic acid (IAA), through the GH3-ILR1-DAO pathway.
  • The process begins with GH3 enzymes converting IAA into storage forms (IAA-aspartate and IAA-glutamate), which can be reverted back to active IAA by ILR1/ILL enzymes.
  • Additionally, DAO1 irreversibly oxidizes these storage forms into inactive compounds, highlighting the significance of this pathway for maintaining auxin levels during plant development.
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The paper investigates the heterogeneous effect of a policy-induced decline in people's mobility on the Japanese labor market outcome during the early COVID-19 period. Regressing individual-level labor market outcomes on prefecture-level mobility changes using policy stringency index as an instrument, our two-stage least squares estimator presents the following findings. First, the number of people absent from work increased for all groups of individuals, but the magnitude was greater for workers with non-regular employment status, low-educated people, females especially with children, and those aged 31 to 45 years.

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This paper empirically examines how the opening of K-12 schools is associated with the spread of COVID-19 using county-level panel data in the United States. As preliminary evidence, our event-study analysis indicates that cases and deaths in counties with in-person or hybrid opening relative to those with remote opening substantially increased after the school opening date, especially for counties without any mask mandate for staff. Our main analysis uses a dynamic panel data model for case and death growth rates, where we control for dynamically evolving mitigation policies, past infection levels, and additive county-level and state-week "fixed" effects.

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This paper quantitatively analyzes the trade-off between job losses and the spread of COVID-19 in Japan. We derive an empirical specification from the social planner's resource constraint under the susceptible, infected, recovered, and deaths (SIRD) model and estimate how job losses and the case growth rate are related to people's mobility using the Japanese prefecture-level panel data on confirmed cases, involuntary job losses, people's mobility, and teleworkability. Our findings are summarized as follows.

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Active membrane transport of plant hormones and their related compounds is an essential process that determines the distribution of the compounds within plant tissues and, hence, regulates various physiological events. Here, we report that the NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER FAMILY 7.3 (NPF7.

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The paper evaluates the dynamic impact of various policies adopted by US states on the growth rates of confirmed Covid-19 cases and deaths as well as social distancing behavior measured by Google Mobility Reports, where we take into consideration people's voluntarily behavioral response to new information of transmission risks in a causal structural model framework. Our analysis finds that both policies and information on transmission risks are important determinants of Covid-19 cases and deaths and shows that a change in policies explains a large fraction of observed changes in social distancing behavior. Our main counterfactual experiments suggest that nationally mandating face masks for employees early in the pandemic could have reduced the weekly growth rate of cases and deaths by more than 10 percentage points in late April and could have led to as much as 19 to 47 percent less deaths nationally by the end of May, which roughly translates into 19 to 47 thousand saved lives.

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Plants have a high regeneration capacity and some plant species can regenerate clone plants, called plantlets, from detached vegetative organs. We previously outlined the molecular mechanisms underlying plantlet regeneration from (Brassicaceae) leaf explants. However, the fundamental difference between the plant species that can and cannot regenerate plantlets from vegetative organs remains unclear.

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Article Synopsis
  • Auxin is a vital plant hormone that influences various growth processes, with indole-3-acetic acid (IAA) as the primary type, while phenylacetic acid (PAA) is another auxin that is often more abundant in certain plants.
  • This study focused on the role of a specific enzyme, UGT84B1, in the metabolism of both IAA and PAA, showing that it can convert IAA and PAA into their respective glucosides more effectively in lab conditions.
  • Despite increased levels of IAA and PAA in mutant plants lacking UGT84B1, no major growth changes were observed, but overexpressing the enzyme caused root development issues, indicating its significant role in
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Auxin is a key regulator of plant growth and development. Indole-3-acetic acid (IAA), a plant auxin, is mainly produced from tryptophan via indole-3-pyruvate (IPA) in both bryophytes and angiosperms. Angiosperms have multiple, well-documented IAA inactivation pathways, involving conjugation to IAA-aspartate (IAA-Asp)/glutamate by the GH3 auxin-amido synthetases, and oxidation to 2-oxindole-3-acetic acid (oxIAA) by the DAO proteins.

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Article Synopsis
  • The phytohormone auxin, particularly indole-3-acetic acid (IAA), is crucial for plant development and moves in a polar manner, creating concentration gradients, while phenylacetic acid (PAA) does not.
  • The study focused on Arabidopsis IAA CARBOXYL METHYLTRANSFERASE 1 (IAMT1), which can convert both IAA and PAA into methyl esters, but is primarily involved in the metabolism of IAA.
  • While overexpressing IAMT1 resulted in reduced IAA levels and auxin-deficient traits, knockout mutants showed normal auxin levels, implying that other proteins in the SABATH family may also contribute to regulating IAA in
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Indole-3-acetamide (IAM) is the first confirmed auxin biosynthetic intermediate in some plant pathogenic bacteria. Exogenously applied IAM or production of IAM by overexpressing the bacterial iaaM gene in Arabidopsis causes auxin overproduction phenotypes. However, it is still inconclusive whether plants use IAM as a key precursor for auxin biosynthesis.

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Endogenous auxin determines the pattern of adventitious shoot formation. Auxin produced in the dominant shoot is transported to the internodal segment and suppresses growth of other shoots. Adventitious shoot formation is required for the propagation of economically important crops and for the regeneration of transgenic plants.

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Phenylacetic acid (PAA) is one type of natural auxin and widely exists in plants. Previous biochemical studies demonstrate that PAA in plants is synthesized from phenylalanine (Phe) via phenylpyruvate (PPA), but the PAA biosynthetic genes and its regulation remain unknown. In this article, we show that the AROGENATE DEHYDRATASE (ADT) family, which catalyzes the conversion of arogenate to Phe, can modulate the levels of PAA in Arabidopsis.

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Article Synopsis
  • Auxin, especially indole-3-acetic acid (IAA), is a key hormone for plant growth, facilitating intercellular communication through polar transport, while another auxin, phenylacetic acid (PAA), lacks this polar movement and its functions are still largely unclear.
  • Researchers discovered that overexpressing the CYP79A2 gene in Arabidopsis led to increased PAA levels and improved lateral root formation, while simultaneously decreasing IAA levels.
  • The study suggests that GH3 genes, responsible for inactivating IAA, can modulate the balance between IAA and PAA, highlighting their roles in plant development regulation.
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