{"id":{"repo_id":"de-montfort","oai_identifier":"oai:dora.dmu.ac.uk:2086/25775"},"canonical_url":"https://search.dev.ndltd.org/etd/de-montfort/oai:dora.dmu.ac.uk:2086/25775","repository":{"repo_id":"de-montfort","name":"De Montfort University","base_url":"https://dora.dmu.ac.uk/server/oai/request"},"display":{"title":"Hormone Binding In Plants","abstract":"The Importance of auxin and auxin receptors in the control of cell division has been investigated through the study of auxin-dependent and auxin-independent strains of suspension-cultured Acer pseudoplatanus L. cells. Parameters studied included growth characteristics, auxin concentration and compartmentation, carrier mediated auxin transport, and cytoplasmic/nuclear binding site (receptor) mediated auxin perception and transduction. Suspension—cultured Acer pseudoplatanus L. cells normally require the auxin 2,4-D to be added to the culture medium for cell division to occur. Transferring these '’2,4-D requiring (DR)” cells into 2,4-D free medium caused a reduction in the rate of cell division. This reduction could be partially reversed by treatment with NPA, an auxin transport inhibitor. A \"no 2,4-D requiring (NDR)” strain has been adapted to auxin-free medium and has similar culture growth parameters to DR strain cells. The intracellular lAA concentrations of DR cells and NDR cells were 0.20 and 1.15 mg 10-6 cells (at day-7 in the batch culture cycle). Auxin compartmentalization studies showed that the cytoplasmic lAA concentration in NDR cells was 4.5 times higher than that in DR cells. When DR cells were treated with NPA, intracellular lAA levels were increased, extracellular lAA levels were decreased and cell division was stimulated. For the NDR strain NPA had no effect on intracellular and extracellular lAA levels but inhibited cell division. Both strains of cells contained a high affinity membrane-bound NPA binding site with a Kd of 7.5 x 10-9 mol dm-3. The number of binding sites changed through the batch culture cycle in both strains but the NDR strain always contained a lower amount (pmoles mg-1 membrane protein) than the DR strain cells. The affinity for 2,3,5-TIBA was about 10 times lower in NDR cells than in DR cells, while there was no difference in their Kd for 2,4-D, 1-NAA or 2-NAA. When the binding sites were solubilized with CHAPS, the Kd for NPA in both strains was shown to be within the same order of magnitude as those of non-solubilized ones, SDS-PAGE showed that the protein populations of cell membranes in the two strains were different. Habituation of the NDR strain to auxin-free medium seems to involve a reduction in the capacity for carrier-mediated auxin efflux. Pi. high affinity cytoplasmic lAA binding site was demonstrated in both strains. Although progress was limited the results showed that these binding sites existed and suggested that they did not change significantly in their capacity throughout the growth cycle of DR cells. At day-7 the number of the binding sites was shown to be the same in two strains and the Kd for lAA was 1.05 x 10-8 mol dm and 1.43 x 10-8 mol dm for DR and NDR cells respectively. The amount of the complexes of lAA and its binding sites was calculated to be 0.194 and 0.619 pmoles 10-6 cells in DR and NDR strains respectively. However, these values were far above the total amount of the detected cytoplasmic auxin binding sites in both strains. The cytoplasmic concentration of IAA in either strain was calculated to be such as to saturate all the binding sites. The present study has emphasised that the availability of both hormone and hormone receptors are determinants of cell division of higher plants.","abstract_html":"The Importance of auxin and auxin receptors in the control of cell division has been investigated through the study of auxin-dependent and auxin-independent strains of suspension-cultured Acer pseudoplatanus L. cells. Parameters studied included growth characteristics, auxin concentration and compartmentation, carrier mediated auxin transport, and cytoplasmic/nuclear binding site (receptor) mediated auxin perception and transduction. Suspension—cultured Acer pseudoplatanus L. cells normally require the auxin 2,4-D to be added to the culture medium for cell division to occur. Transferring these '’2,4-D requiring (DR)” cells into 2,4-D free medium caused a reduction in the rate of cell division. This reduction could be partially reversed by treatment with NPA, an auxin transport inhibitor. A "no 2,4-D requiring (NDR)” strain has been adapted to auxin-free medium and has similar culture growth parameters to DR strain cells. The intracellular lAA concentrations of DR cells and NDR cells were 0.20 and 1.15 mg 10-6 cells (at day-7 in the batch culture cycle). Auxin compartmentalization studies showed that the cytoplasmic lAA concentration in NDR cells was 4.5 times higher than that in DR cells. When DR cells were treated with NPA, intracellular lAA levels were increased, extracellular lAA levels were decreased and cell division was stimulated. For the NDR strain NPA had no effect on intracellular and extracellular lAA levels but inhibited cell division. Both strains of cells contained a high affinity membrane-bound NPA binding site with a Kd of 7.5 x 10-9 mol dm-3. The number of binding sites changed through the batch culture cycle in both strains but the NDR strain always contained a lower amount (pmoles mg-1 membrane protein) than the DR strain cells. The affinity for 2,3,5-TIBA was about 10 times lower in NDR cells than in DR cells, while there was no difference in their Kd for 2,4-D, 1-NAA or 2-NAA. When the binding sites were solubilized with CHAPS, the Kd for NPA in both strains was shown to be within the same order of magnitude as those of non-solubilized ones, SDS-PAGE showed that the protein populations of cell membranes in the two strains were different. Habituation of the NDR strain to auxin-free medium seems to involve a reduction in the capacity for carrier-mediated auxin efflux. Pi. high affinity cytoplasmic lAA binding site was demonstrated in both strains. Although progress was limited the results showed that these binding sites existed and suggested that they did not change significantly in their capacity throughout the growth cycle of DR cells. At day-7 the number of the binding sites was shown to be the same in two strains and the Kd for lAA was 1.05 x 10-8 mol dm and 1.43 x 10-8 mol dm for DR and NDR cells respectively. The amount of the complexes of lAA and its binding sites was calculated to be 0.194 and 0.619 pmoles 10-6 cells in DR and NDR strains respectively. However, these values were far above the total amount of the detected cytoplasmic auxin binding sites in both strains. The cytoplasmic concentration of IAA in either strain was calculated to be such as to saturate all the binding sites. The present study has emphasised that the availability of both hormone and hormone receptors are determinants of cell division of higher plants.","abstract_has_math":false,"creators":["Xing, Ti"],"institution":"De Montfort University","degree_name":"PhD","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":1990,"date_issued":"1990-11","date_published":"1990-11","updated_at":"2026-07-24T06:18:49Z","subjects":[],"languages":[],"rights":[],"rights_urls":["https://dora.dmu.ac.uk/bitstreams/0dd677f7-cb3a-425c-8909-37e7c7827d5b/download"],"identifier_entries":[]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Xing, Ti"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["1990-11"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Faculty of Health and Life Sciences"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["De Montfort University"]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["https://hdl.handle.net/2086/25775"]},{"key":"dc:type","label":"Dc Type","values":["Thesis or dissertation"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["PhD"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["https://dora.dmu.ac.uk/bitstreams/0dd677f7-cb3a-425c-8909-37e7c7827d5b/download"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://dora.dmu.ac.uk/bitstreams/2d11ffc8-0c1b-4335-b290-7cb0602811ba/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The Importance of auxin and auxin receptors in the control of cell division has been investigated through the study of auxin-dependent and auxin-independent strains of suspension-cultured Acer pseudoplatanus L. cells. Parameters studied included growth characteristics, auxin concentration and compartmentation, carrier mediated auxin transport, and cytoplasmic/nuclear binding site (receptor) mediated auxin perception and transduction. Suspension—cultured Acer pseudoplatanus L. cells normally require the auxin 2,4-D to be added to the culture medium for cell division to occur. Transferring these '’2,4-D requiring (DR)” cells into 2,4-D free medium caused a reduction in the rate of cell division. This reduction could be partially reversed by treatment with NPA, an auxin transport inhibitor. A \"no 2,4-D requiring (NDR)” strain has been adapted to auxin-free medium and has similar culture growth parameters to DR strain cells. The intracellular lAA concentrations of DR cells and NDR cells were 0.20 and 1.15 mg 10-6 cells (at day-7 in the batch culture cycle). Auxin compartmentalization studies showed that the cytoplasmic lAA concentration in NDR cells was 4.5 times higher than that in DR cells. When DR cells were treated with NPA, intracellular lAA levels were increased, extracellular lAA levels were decreased and cell division was stimulated. For the NDR strain NPA had no effect on intracellular and extracellular lAA levels but inhibited cell division. Both strains of cells contained a high affinity membrane-bound NPA binding site with a Kd of 7.5 x 10-9 mol dm-3. The number of binding sites changed through the batch culture cycle in both strains but the NDR strain always contained a lower amount (pmoles mg-1 membrane protein) than the DR strain cells. The affinity for 2,3,5-TIBA was about 10 times lower in NDR cells than in DR cells, while there was no difference in their Kd for 2,4-D, 1-NAA or 2-NAA. When the binding sites were solubilized with CHAPS, the Kd for NPA in both strains was shown to be within the same order of magnitude as those of non-solubilized ones, SDS-PAGE showed that the protein populations of cell membranes in the two strains were different. Habituation of the NDR strain to auxin-free medium seems to involve a reduction in the capacity for carrier-mediated auxin efflux. Pi. high affinity cytoplasmic lAA binding site was demonstrated in both strains. Although progress was limited the results showed that these binding sites existed and suggested that they did not change significantly in their capacity throughout the growth cycle of DR cells. At day-7 the number of the binding sites was shown to be the same in two strains and the Kd for lAA was 1.05 x 10-8 mol dm and 1.43 x 10-8 mol dm for DR and NDR cells respectively. The amount of the complexes of lAA and its binding sites was calculated to be 0.194 and 0.619 pmoles 10-6 cells in DR and NDR strains respectively. However, these values were far above the total amount of the detected cytoplasmic auxin binding sites in both strains. The cytoplasmic concentration of IAA in either strain was calculated to be such as to saturate all the binding sites. 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Suspension—cultured Acer pseudoplatanus L. cells normally require the auxin 2,4-D to be added to the culture medium for cell division to occur. Transferring these '’2,4-D requiring (DR)” cells into 2,4-D free medium caused a reduction in the rate of cell division. This reduction could be partially reversed by treatment with NPA, an auxin transport inhibitor. A \"no 2,4-D requiring (NDR)” strain has been adapted to auxin-free medium and has similar culture growth parameters to DR strain cells. The intracellular lAA concentrations of DR cells and NDR cells were 0.20 and 1.15 mg 10-6 cells (at day-7 in the batch culture cycle). Auxin compartmentalization studies showed that the cytoplasmic lAA concentration in NDR cells was 4.5 times higher than that in DR cells. When DR cells were treated with NPA, intracellular lAA levels were increased, extracellular lAA levels were decreased and cell division was stimulated. For the NDR strain NPA had no effect on intracellular and extracellular lAA levels but inhibited cell division. Both strains of cells contained a high affinity membrane-bound NPA binding site with a Kd of 7.5 x 10-9 mol dm-3. The number of binding sites changed through the batch culture cycle in both strains but the NDR strain always contained a lower amount (pmoles mg-1 membrane protein) than the DR strain cells. The affinity for 2,3,5-TIBA was about 10 times lower in NDR cells than in DR cells, while there was no difference in their Kd for 2,4-D, 1-NAA or 2-NAA. When the binding sites were solubilized with CHAPS, the Kd for NPA in both strains was shown to be within the same order of magnitude as those of non-solubilized ones, SDS-PAGE showed that the protein populations of cell membranes in the two strains were different. Habituation of the NDR strain to auxin-free medium seems to involve a reduction in the capacity for carrier-mediated auxin efflux. Pi. high affinity cytoplasmic lAA binding site was demonstrated in both strains. Although progress was limited the results showed that these binding sites existed and suggested that they did not change significantly in their capacity throughout the growth cycle of DR cells. At day-7 the number of the binding sites was shown to be the same in two strains and the Kd for lAA was 1.05 x 10-8 mol dm and 1.43 x 10-8 mol dm for DR and NDR cells respectively. The amount of the complexes of lAA and its binding sites was calculated to be 0.194 and 0.619 pmoles 10-6 cells in DR and NDR strains respectively. However, these values were far above the total amount of the detected cytoplasmic auxin binding sites in both strains. The cytoplasmic concentration of IAA in either strain was calculated to be such as to saturate all the binding sites. 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