The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform

Sjef Smeekens - One of the best experts on this subject based on the ideXlab platform.

  • the arabidopsis sucrose uncoupled 6 gene is identical to Abscisic Acid insensitive 4 involvement of Abscisic Acid in sugar responses
    Plant Journal, 2000
    Co-Authors: Casper Huijser, A J Kortstee, Jonatas V Pego, Peter Weisbeek, Ellen Wisman, Sjef Smeekens
    Abstract:

    : In plants, sugars act as signalling molecules that control many aspects of metabolism and development. Arabidopsis plants homozygous for the recessive sucrose uncoupled-6 (sun6) mutation show a reduced sensitivity to sugars for processes such as photosynthesis, gene expression and germination. The sun6 mutant is insensitive to sugars that are substrates for hexokinase, suggesting that SUN6 might play a role in hexokinase-dependent sugar responses. The SUN6 gene was cloned by transposon tagging and analysis showed it to be identical to the previously described Abscisic Acid INSENSITIVE-4 (ABI4) gene. Our analysis suggests the involvement of Abscisic Acid and components of the Abscisic Acid signal transduction cascade in a hexokinase-dependent sugar response pathway. During the plant life cycle, SUN6/ABI4 may be involved in controlling metabolite availability in an Abscisic Acid- and sugar-dependent way.

  • The Arabidopsis SUCROSE UNCOUPLED‐6 gene is identical to Abscisic Acid INSENSITIVE‐4: involvement of Abscisic Acid in sugar responses
    The Plant journal : for cell and molecular biology, 2000
    Co-Authors: Casper Huijser, A J Kortstee, Jonatas V Pego, Peter Weisbeek, Ellen Wisman, Sjef Smeekens
    Abstract:

    In plants, sugars act as signalling molecules that control many aspects of metabolism and development. Arabidopsis plants homozygous for the recessive sucrose uncoupled-6 (sun6) mutation show a reduced sensitivity to sugars for processes such as photosynthesis, gene expression and germination. The sun6 mutant is insensitive to sugars that are substrates for hexokinase, suggesting that SUN6 might play a role in hexokinase-dependent sugar responses. The SUN6 gene was cloned by transposon tagging and analysis showed it to be identical to the previously described Abscisic Acid INSENSITIVE-4 (ABI4) gene. Our analysis suggests the involvement of Abscisic Acid and components of the Abscisic Acid signal transduction cascade in a hexokinase-dependent sugar response pathway. During the plant life cycle, SUN6/ABI4 may be involved in controlling metabolite availability in an Abscisic Acid- and sugar-dependent way.

G. R. Richardson - One of the best experts on this subject based on the ideXlab platform.

  • Carotenogenic and Abscisic Acid biosynthesizing activity in a cell‐free system
    Physiologia Plantarum, 1997
    Co-Authors: A.k. Cowan, G. R. Richardson
    Abstract:

    Abscisic Acid is considered an apocarotenoid formed by cleavage of a C-40 precursor and subsequent oxidation of xanthoxin and Abscisic aldehyde. Confirmation of this reaction sequence is still awaited, and might best be achieved using a cell-free system capable of both carotenoid and Abscisic Acid biosynthesis. An Abscisic Acid biosynthesizing cell-free system, prepared from flavedo of mature orange fruits, was used to demonstrate conversion of farnesyl pyrophosphate, geranylgeranyl pyrophosphate and all-trans-β-carotene into a range of β,β-xanthophylls, xanthoxin, xanthoxin Acid, 1',4'-trans-Abscisic Acid diol and Abscisic Acid. Identification of product carotenoids was achieved by high-performance liquid chromatography and on-line spectral analysis of individual components together with co-chromatography. Putative C-15 intermediates and product Abscisic Acid were identified by combined capillary gas chromatography-mass spectrometry. Kinetic studies revealed that β-carotene, formed from either farnesyl pyrophosphate or geranylgeranyl pyrophosphate, reached a maximum within 30 min of initiation of the reaction. Thereafter, β-carotene levels declined exponentially. Catabolism of substrate β-carotene into xanthophylls, putative Abscisic Acid precursors and product Abscisic Acid was restricted to the all-trans-isomer. However, when a combination of all-trans- and 9-cis-β-carotene in the ratio 1:1 was used as substrate, formation of Abscisic Acid and related metabolites was enhanced. Biosynthetically prepared [ 14 C]-all-trans-violaxanthin, [ 14 C]-all-trans-neoxanthin and [ 14 C]-9'-cis-neoxanthin were used as substrates to confirm the metabolic interrelationship between carotenoids and Abscisic Acid. The results are consistent with 9'-cis-neoxanthin being the immediate carotenoid precursor to ABA, which is oxidatively cleaved to produce xanthoxin. Formation of Abscisic aldehyde was not observed. Rather, xanthoxin appeared to be converted to Abscisic Acid via xanthoxin Acid and 1',4'-trans-Abscisic Acid diol. An alternative pathway for Abscisic Acid biosynthesis is therefore proposed.

  • Stress‐induced Abscisic Acid transients and stimulus‐response‐coupling
    Physiologia Plantarum, 1997
    Co-Authors: A.k. Cowan, G. R. Richardson, J. C. G. Maurel
    Abstract:

    Loss of cell turgor and distortion of the plasma membrane occur as a result of dehydration and precede the stress-induced bulk increase in concentration of tissue Abscisic Acid. The latter has been correlated with induction of stress-related gene expression. However, several different stresses may trigger the same coupling mechanism. Thus, at least three signalling pathways have been proposed: Abscisic Acid-requiring, Abscisic Acid-responsive, and mechanosensory. In this paper, the role and contribution of stress-induced Abscisic Acid transients is examined in an attempt to explain apparent Abscisic Acid-dependent and -independent stimulus-response-coupling. Early, intermediate, and late response stages are defined within the stress-induced Abscisic Acid transient and at least four signalling mechanisms are identified. These include, early and late intracellular modulation of gene expression through derepression and/or negative regulation, rapid membrane-initiated calcium release and ion channel activation, and late (slow) hormone-receptor induction of gene expression. An assessment of these proposed ABA signalling mechanisms in terms of ABA-dependent and -independent stimulus-response-coupling strongly suggests that rapid responses may not be a prerequisite for slow responses and that the receptor proteins involved have different steric requirements, i.e., they are tissue- and/or cell-specific.

A.k. Cowan - One of the best experts on this subject based on the ideXlab platform.

  • Abscisic Acid content of Citrus flavedo in relation to colour development
    Journal of Horticultural Science, 2015
    Co-Authors: Gaynor R. Richardson, A.k. Cowan
    Abstract:

    SummaryThe relationship between endogenous Abscisic Acid concentrations and the development of colour was examined in six cultivars of Citrus sinensis. Abscisic Acid content increased throughout the course of colour development and reached a maximum at time of colour break. Late-maturing cultivars accumulated substantially more Abscisic Acid and development of colour occurred visibly later than in ‘Navel’ selections. A decline in Abscisic Acid concentration occurred concomitantly with full expression of colour. Analysis of the pigment composition of flavedo from Citrus sinensis cv. Midknight revealed that development of orange colour was associated with a decline in levels of β,β-carotenoids, an increase in violaxanthin monoesters and formation of xanthophyll acyl esters.

  • Carotenogenic and Abscisic Acid biosynthesizing activity in a cell‐free system
    Physiologia Plantarum, 1997
    Co-Authors: A.k. Cowan, G. R. Richardson
    Abstract:

    Abscisic Acid is considered an apocarotenoid formed by cleavage of a C-40 precursor and subsequent oxidation of xanthoxin and Abscisic aldehyde. Confirmation of this reaction sequence is still awaited, and might best be achieved using a cell-free system capable of both carotenoid and Abscisic Acid biosynthesis. An Abscisic Acid biosynthesizing cell-free system, prepared from flavedo of mature orange fruits, was used to demonstrate conversion of farnesyl pyrophosphate, geranylgeranyl pyrophosphate and all-trans-β-carotene into a range of β,β-xanthophylls, xanthoxin, xanthoxin Acid, 1',4'-trans-Abscisic Acid diol and Abscisic Acid. Identification of product carotenoids was achieved by high-performance liquid chromatography and on-line spectral analysis of individual components together with co-chromatography. Putative C-15 intermediates and product Abscisic Acid were identified by combined capillary gas chromatography-mass spectrometry. Kinetic studies revealed that β-carotene, formed from either farnesyl pyrophosphate or geranylgeranyl pyrophosphate, reached a maximum within 30 min of initiation of the reaction. Thereafter, β-carotene levels declined exponentially. Catabolism of substrate β-carotene into xanthophylls, putative Abscisic Acid precursors and product Abscisic Acid was restricted to the all-trans-isomer. However, when a combination of all-trans- and 9-cis-β-carotene in the ratio 1:1 was used as substrate, formation of Abscisic Acid and related metabolites was enhanced. Biosynthetically prepared [ 14 C]-all-trans-violaxanthin, [ 14 C]-all-trans-neoxanthin and [ 14 C]-9'-cis-neoxanthin were used as substrates to confirm the metabolic interrelationship between carotenoids and Abscisic Acid. The results are consistent with 9'-cis-neoxanthin being the immediate carotenoid precursor to ABA, which is oxidatively cleaved to produce xanthoxin. Formation of Abscisic aldehyde was not observed. Rather, xanthoxin appeared to be converted to Abscisic Acid via xanthoxin Acid and 1',4'-trans-Abscisic Acid diol. An alternative pathway for Abscisic Acid biosynthesis is therefore proposed.

  • Stress‐induced Abscisic Acid transients and stimulus‐response‐coupling
    Physiologia Plantarum, 1997
    Co-Authors: A.k. Cowan, G. R. Richardson, J. C. G. Maurel
    Abstract:

    Loss of cell turgor and distortion of the plasma membrane occur as a result of dehydration and precede the stress-induced bulk increase in concentration of tissue Abscisic Acid. The latter has been correlated with induction of stress-related gene expression. However, several different stresses may trigger the same coupling mechanism. Thus, at least three signalling pathways have been proposed: Abscisic Acid-requiring, Abscisic Acid-responsive, and mechanosensory. In this paper, the role and contribution of stress-induced Abscisic Acid transients is examined in an attempt to explain apparent Abscisic Acid-dependent and -independent stimulus-response-coupling. Early, intermediate, and late response stages are defined within the stress-induced Abscisic Acid transient and at least four signalling mechanisms are identified. These include, early and late intracellular modulation of gene expression through derepression and/or negative regulation, rapid membrane-initiated calcium release and ion channel activation, and late (slow) hormone-receptor induction of gene expression. An assessment of these proposed ABA signalling mechanisms in terms of ABA-dependent and -independent stimulus-response-coupling strongly suggests that rapid responses may not be a prerequisite for slow responses and that the receptor proteins involved have different steric requirements, i.e., they are tissue- and/or cell-specific.

Casper Huijser - One of the best experts on this subject based on the ideXlab platform.

  • the arabidopsis sucrose uncoupled 6 gene is identical to Abscisic Acid insensitive 4 involvement of Abscisic Acid in sugar responses
    Plant Journal, 2000
    Co-Authors: Casper Huijser, A J Kortstee, Jonatas V Pego, Peter Weisbeek, Ellen Wisman, Sjef Smeekens
    Abstract:

    : In plants, sugars act as signalling molecules that control many aspects of metabolism and development. Arabidopsis plants homozygous for the recessive sucrose uncoupled-6 (sun6) mutation show a reduced sensitivity to sugars for processes such as photosynthesis, gene expression and germination. The sun6 mutant is insensitive to sugars that are substrates for hexokinase, suggesting that SUN6 might play a role in hexokinase-dependent sugar responses. The SUN6 gene was cloned by transposon tagging and analysis showed it to be identical to the previously described Abscisic Acid INSENSITIVE-4 (ABI4) gene. Our analysis suggests the involvement of Abscisic Acid and components of the Abscisic Acid signal transduction cascade in a hexokinase-dependent sugar response pathway. During the plant life cycle, SUN6/ABI4 may be involved in controlling metabolite availability in an Abscisic Acid- and sugar-dependent way.

  • The Arabidopsis SUCROSE UNCOUPLED‐6 gene is identical to Abscisic Acid INSENSITIVE‐4: involvement of Abscisic Acid in sugar responses
    The Plant journal : for cell and molecular biology, 2000
    Co-Authors: Casper Huijser, A J Kortstee, Jonatas V Pego, Peter Weisbeek, Ellen Wisman, Sjef Smeekens
    Abstract:

    In plants, sugars act as signalling molecules that control many aspects of metabolism and development. Arabidopsis plants homozygous for the recessive sucrose uncoupled-6 (sun6) mutation show a reduced sensitivity to sugars for processes such as photosynthesis, gene expression and germination. The sun6 mutant is insensitive to sugars that are substrates for hexokinase, suggesting that SUN6 might play a role in hexokinase-dependent sugar responses. The SUN6 gene was cloned by transposon tagging and analysis showed it to be identical to the previously described Abscisic Acid INSENSITIVE-4 (ABI4) gene. Our analysis suggests the involvement of Abscisic Acid and components of the Abscisic Acid signal transduction cascade in a hexokinase-dependent sugar response pathway. During the plant life cycle, SUN6/ABI4 may be involved in controlling metabolite availability in an Abscisic Acid- and sugar-dependent way.

Shigeo Yoshida - One of the best experts on this subject based on the ideXlab platform.

  • 4′-Alkoxy derivatives of Abscisic Acid: a promising new probe for mechanisms of Abscisic Acid perceptions
    Plant Growth Regulation, 2002
    Co-Authors: Tadao Asami, Yong Ki Min, Noboru Murofushi, Sun-young Han, Nobutaka Kitahata, Shigeo Yoshida
    Abstract:

    The preparation of new compounds for exploring the molecular andbiochemical mechanisms of Abscisic Acid signal perception is described. The4′-carbonyl group of Abscisic Acid was replaced with either benzyloxy orn-octyloxy groups. Both modified products possessedABA-like activity in bioassays using barley aleurone protoplasts. The benzyloxyderivative was active in dehydrin induction tests, but not in inhibition ofα-amylase induction tests. The difference in the activity of this chemical inthe two assay systems suggests that the perception system for the inhibition ofamylase induction systems differs from that of dehydrin induction.

  • Synthesis and biological activity of 4'-methoxy derivatives of Abscisic Acid.
    Bioorganic & medicinal chemistry letters, 2000
    Co-Authors: Tadao Asami, Yong Ki Min, Noboru Murofushi, Takeshi Nakano, Tomoki Matsuyama, Isomaro Yamaguchi, Shigeo Yoshida
    Abstract:

    Replacing the 4'-carbonyl group of Abscisic Acid with a methoxy group does not affect the Abscisic Acid (ABA)-like activities of the product in barley aleurone protoplasts, although the reduction of ABA to 4'-hydroxyl derivatives significantly reduces the ABA-like activity of the products. This suggests that methoxy derivatives of Abscisic Acid might be used to produce probes for ABA binding proteins.

  • Fluorescence-labeled Abscisic Acid Possessing Abscisic Acid-like Activity in Barley Aleurone Protoplasts
    Bioscience Biotechnology and Biochemistry, 1997
    Co-Authors: Tadao Asami, Ling Tao, Shin Yamamoto, Masumi Robertson, Yong Ki Min, Noboru Murofushi, Shigeo Yoshida
    Abstract:

    Novel fluorescence-labeled Abscisic Acid was synthesized by introducing a fluorescent functional group into the 4' position of Abscisic Acid via 4-aminophenylcarbohydrazide as a spacer. The inhibitory activity toward amylase induction by this chemical was evaluated by using aleurone protoplasts, and it was demonstrated that the analogue possessed Abscisic Acid-like activity.