Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

We investigated the role of ethylene and auxin in regulating the growth and morphology of roots during mechanical impedance by developing a new growing system and using the model plant Arabidopsis (Arabidopsis thaliana). The Arabidopsis seedlings grown horizontally on a dialysis membrane-covered agar plate encountered adequate mechanical impedance as the roots showed characteristic ethylene phenotypes: 2-fold reduction in root growth, increase in root diameter, decrease in cell elongation, and ectopic root hair formation. The root phenotype characterization of various mutants having altered response to ethylene biosynthesis or signaling, the effect of ethylene inhibitors on mechanically impeded roots, and transcription profiling of the ethylene-responsive genes led us to conclude that enhanced ethylene response plays a primary role in changing root morphology and development during mechanical impedance. Further, the differential sensitivity of horizontally and vertically grown roots toward exogenous ethylene suggested that ethylene signaling plays a critical role in enhancing the ethylene response. We subsequently demonstrated that the enhanced ethylene response also affects the auxin response in roots. Taken together, our results provide a new insight into the role of ethylene in changing root morphology during mechanical impedance.

DOI： 10.1104/pp.107.115519

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Language：English   Publishing type：Research paper (scientific journal)  

In Arabidopsis thaliana, the ACL5 gene encodes thermospermine synthase and its mutant, acl5, exhibits a dwarf phenotype with excessive xylem formation. Studies of suppressor mutants of acl5 reveal the involvement of thermospermine in enhancing mRNA translation of the SAC51 gene family. We show here that a mutant, sac59, which partially suppresses the acl5 phenotype, has a point mutation in JMJ22 encoding a D6-class Jumonji C protein (JMJD6). A T-DNA insertion allele, jmj22-2, also partially suppressed the acl5 phenotype while mutants of its closest two homologs JMJ21 and JMJ20 had no such effects, suggesting a unique role for JMJ22 in plant development. We found that mRNAs of the SAC51 family are more stabilized in acl5 jmj22-2 than in acl5.

DOI： 10.1002/1873-3468.14470

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

In plants, many of the enzymes in polyamine metabolism are encoded by multiple genes, whose expressions are differentially regulated under different physiological conditions. For comprehensive understanding of their regulation during the seedling growth stage, we examined the expression of polyamine metabolic genes in response to polyamines and stress-related plant hormones in Arabidopsis thaliana. While confirming previous findings such as induction of many of the genes by abscisic acid, induction of arginase genes and a copper amine oxidase gene, CuAOα3, by methyl jasmonate, that of an arginine decarboxylase gene, ADC2, and a spermine synthase gene, SPMS, by salicylic acid, and negative feedback regulation of thermospermine biosynthetic genes by thermospermine, our results showed that expressions of most of the genes are not responsive to exogenous polyamines. We thus examined expression of OsPAO6, which encodes an apoplastic polyamine oxidase and is strongly induced by polyamines in rice, by using the promoter-GUS fusion in transgenic Arabidopsis seedlings. The GUS activity was increased by treatment with methyl jasmonate but neither by polyamines nor by other plant hormones, suggesting a difference in the response to polyamines between Arabidopsis and rice. Our results provide a framework to study regulatory modules directing expression of each polyamine metabolic gene.

DOI： 10.3390/cells10123283

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/15592324.2019.1669417

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1111/tpj.14448

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

Auxin transport plays a significant role modifying plant growth and development in response to environmental signals such as light and gravity. However, the effect of humidity on auxin transport is rarely documented. It is shown here that the transport of labelled indole-3-acetic acid (IAA) from the shoot to the root is accelerated in rice (Oryza sativa L. ssp. indica cv. IR8) seedlings grown under saturated humidity (SH-seedlings) compared with plants grown under normal humidity (NH-seedlings). The development of lateral roots in SH-seedlings was greatly enhanced compared with NH-seedlings. Removal of the shoot from SH-seedlings reduced the density of lateral roots, and the application of IAA to the cut stem restored the lateral root density, while the decapitation of NH-seedlings did not alter lateral root development. Phloem-based auxin transport appeared responsible for enhanced lateral root formation in SH-seedlings since (i) the rate of IAA transport from the shoot to the root tip was greater than 3.5 cm h(-1) and (ii) naphthylphthalamic acid (NPA)-induced reduction of polar auxin transport in the shoot did not influence the number of lateral roots in SH-seedlings. It is proposed that high humidity conditions accelerate the phloem-based transport of IAA from the leaf to the root, resulting in an increase in the number of lateral roots.

DOI： 10.1093/jxb/erm026

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We propose a simple and a powerful method to enhance the enantioselectivity for lipase-catalysed transformations in organic solvents by an addition of metal ion-containing water to the reaction mixture. In this paper, various metal ions such as LiCl or MgCl2 are tested to improve the enantioselectivity for the model reactions. The enantioselectivities obtained are dramatically enhanced, the E values of which are about 100-fold as compared with the ordinary conditions without a metal ion, for example, E = 200 by addition of LiCl. Furthermore, lowering the reaction temperature led to an almost perfect enantioselectivity of lipase in the presence of a metal ion, for example, E = 1300 by addition of LiCl. Also, a mechanism for the drastic enhancement by metal ions is discussed briefly on the basis of the EPR spectroscopic study and the initial rate for each enantiomer of the substrate.

DOI： 10.1039/b514885e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

For lipase-catalyzed reactions of 2-(4-substitued phenoxy)propionic acids with alcohols in organic solvents containing a small amount of water, the increase of the lipase flexibility brought about by addition of water is found to be favorable for the induced-fit motion of the lipase for the correctly binding enantiomer of the substrate used, thus resulting in the improvement of the lipase enantioselectivity. In particular, for the reaction of the substrate with rich pi electron density on its aromatic ring, the enantioselectivity was much more sensitive to the change of the lipase flexibility. Thus, in the induced fit motion, the CH...pi association between amino acids side chains around the lipase's active site and the aromatic ring of the correctly binding enantiomer is assumed to accelerate the accommodation Of the Substrate into the lipase's active site and the stabilization of the complex between the enzyme and the substrate. This assumption is also Supported by a discussion based on the value of the Michaelis constant obtained. Furthermore, on the basis of a model concerning the acyl-enzyme structure for the incorrectly binding enantiomer, the long alkyl chain alcohols as a nucleophile are found to improve the lipase enantioselectivity markedly.

DOI： 10.1246/bcsj.77.543

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

The behavior of the enantioselectivity of Candida rugosa lipase was investigated in the esterification of 2-(4-substituted phenoxy)propionic acids with 1-butanol in aliphatic, aromatic, and ethereal solvents. The observed enantioselectivity (E value) was greatly affected by the solvent nature. Two key solvent characteristics, dielectric constant (E) and hydrophobicity (log P), failed to explain the solvent effects on the E value. On the other hand, the variation of the E value was found to be successfully correlated with the lipase flexibility brought about by the solvent effects, the flexibility of which was estimated by the ESR measurements of the spin-labeled lipase. Although organic chemists should often undertake a solvent screening step in the biocatalytic asymmetric resolutions, the obtained correlation will provide a useful guide in the solvent optimization step.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC PUBL  

Semi-purified lipases from Candida rugosa, Pseudomonas cepacia and Alcaligenes sp. were chemically modified with a wide range of hydrophobic groups such as benzyloxycarbonyl, p-nitrobenzyloxycarbonyl, p-methoxybenzyloxycarbonyl, t-butoxycarbonyl, lauroyl and acetyl moieties. The Candida rugosa lipase MY modified with the benzyloxycarbonyl group (modification ratio = 84%) brought about a 15-fold increase in enantioselectivity (E value) towards the hydrolysis of racemic butyl 2-(4-ethylphenoxy) propionate in an aqueous buffer solution, although the enzymatic activity was decreased. The origin of the enantioselectivity enhancement by chemical modification of the lipase is attributed to a significant deceleration in the initial reaction rate for the incorrectly binding enantiomer.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

The enantioselectivity for the lipase-catalyzed esterifications in an organic solvent was found to be enhanced by addition of (+)- or (-)-camphor as a chiral additive. A more remarkable enhancement of its enantioselectivity was brought about by the cooperative effects of two kinds of additives: (-)-camphor and water.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC PUBL  

The hydrolysis of racemic butyl 2-(4-substituted phenoxy)propionates having various substituents catalyzed by lipase MY from Candida rugosa was achieved in di-isopropyl ether containing 0.75% (v/v) of 2.4 M LiCl or 1.2 M MgCl2 aqueous solution. Water molecules hydrated to the metal ion in isopropyl ether acted as a nucleophile to cause the hydrolysis of these esters as with water alone. Metal ions used significantly enhanced their enantioselectivities by 100-fold or above, as compared with the ordinary reaction media.

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Language：English   Publishing type：Research paper (scientific journal)  

CiNii Article

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

By the addition of metal ion-containing water, a marked enhancement of the enantioselectivity for the lipase-catalysed esterification of 2-(4-substituted-phenoxy)propionic acids in (Pr2O)-O-i was observed, the mechanism of which will be discussed briefly on the basis of the initial rate obtained for each enantiomer of the substrate.

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Event date： 2021.3.14 - 2021.3.16

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：松江   Country：Japan  

Event date： 2020.3.19 - 2020.3.21

Language：Japanese  

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Event date： 2020.3.19 - 2020.3.21

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：大阪   Country：Japan  

Event date： 2019.9.15 - 2019.9.17

Language：Japanese   Presentation type：Poster presentation  

Venue：仙台   Country：Japan  

Event date： 2019.7.7 - 2019.7.12

Language：English   Presentation type：Poster presentation  

Venue：Cambridge, UK   Country：United Kingdom  

Event date： 2019.7.7 - 2019.7.12

Language：English   Presentation type：Poster presentation  

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Event date： 2019.3.13 - 2019.3.15

Language：Japanese   Presentation type：Poster presentation  

Venue：名古屋   Country：Japan  

Event date： 2019.3.13 - 2019.3.15

Language：Japanese   Presentation type：Poster presentation  

Venue：名古屋   Country：Japan  

Event date： 2019.3.13 - 2019.3.15

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋   Country：Japan  

Event date： 2019.3.13 - 2019.3.15

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2019.3.13 - 2019.3.15

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2019.3.13 - 2019.3.15

Language：Japanese   Presentation type：Poster presentation  

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