THE CONSEQUENCES OF BROMODEOXYURIDINE TREATMENT IN PLANT TISSUE CULTURES (REGENERATION, REPLICATION).

Persistent Link:
http://hdl.handle.net/10150/183989
Title:
THE CONSEQUENCES OF BROMODEOXYURIDINE TREATMENT IN PLANT TISSUE CULTURES (REGENERATION, REPLICATION).
Author:
THOMAS, JOHN CALVIN.
Issue Date:
1986
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Plant tissue culture regeneration is chiefly regulated by exogenous phytohormones. To stop regeneration and induce undifferentiated callus growth auxins are used. Unfortunately auxins influence many plant responses, most unrelated to development. Using the thymidine analogue 5-bromodeoxyuridine (BrdU) a phytohormone independent means for differentiation inhibition has been developed. Studies were focused on the target site and mechanism of BrdU action. The BrdU inhibited step in development is indicative of a plant response necessary for normal differentiation. BrdU (5-30 uM) interrupts callus growth in all tested plants. Exogenous cytokinin does not restore growth while thymidine and deoxycytidine rescue plant growth and differentiation in the presence of BrdU. Endogenous cytokinin levels are not greatly affected by subtoxic BrdU levels and indicate that cytokinin and BrdU act upon independent sites. Domestic carrot cells were used in further studies. Normally carrot cells are undifferentiated in medium with the auxin 2,4D. When 2,4D is removed, somatic embryogenesis takes place. By including 5 uM BrdU in the hormoneless medium, the cells fail to differentiate. The growth of carrots in 2,4D is not affected by 5 uM BrdU. Thus, BrdU influences growth during differentiation to a greater extent than the growth of callus cells. BrdU is effective in halting development when applied 0-24 hours after differentiation induction. An event required for differentiation (the first and second replications) must take place at this time. BrdU action begins with DNA incorporation. The consequent cellular replication becomes slowed and DNA repair results. At the same time RNA and protein levels are similar in BrdU treated and untreated cultures. BrdU thymidine substitution into DNA increases from 28% (2 days) to 68% (3 days) after embryogenic induction. A second BrdU effect follows DNA incorporation. Factors (MIFs) in the medium of BrdU treated cells arrest differentiation. After BrdU is repaired from the DNA, the cells are only able to differentiate after a medium change. Understanding MIF production could explain why some plants differentiate more readily than others. BrdU provides the means for further study of MIF's in the auxin-free inhibition of development.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Plant tissue culture.; Bromodeoxyuridine.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Genetics; Graduate College
Degree Grantor:
University of Arizona

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleTHE CONSEQUENCES OF BROMODEOXYURIDINE TREATMENT IN PLANT TISSUE CULTURES (REGENERATION, REPLICATION).en_US
dc.creatorTHOMAS, JOHN CALVIN.en_US
dc.contributor.authorTHOMAS, JOHN CALVIN.en_US
dc.date.issued1986en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractPlant tissue culture regeneration is chiefly regulated by exogenous phytohormones. To stop regeneration and induce undifferentiated callus growth auxins are used. Unfortunately auxins influence many plant responses, most unrelated to development. Using the thymidine analogue 5-bromodeoxyuridine (BrdU) a phytohormone independent means for differentiation inhibition has been developed. Studies were focused on the target site and mechanism of BrdU action. The BrdU inhibited step in development is indicative of a plant response necessary for normal differentiation. BrdU (5-30 uM) interrupts callus growth in all tested plants. Exogenous cytokinin does not restore growth while thymidine and deoxycytidine rescue plant growth and differentiation in the presence of BrdU. Endogenous cytokinin levels are not greatly affected by subtoxic BrdU levels and indicate that cytokinin and BrdU act upon independent sites. Domestic carrot cells were used in further studies. Normally carrot cells are undifferentiated in medium with the auxin 2,4D. When 2,4D is removed, somatic embryogenesis takes place. By including 5 uM BrdU in the hormoneless medium, the cells fail to differentiate. The growth of carrots in 2,4D is not affected by 5 uM BrdU. Thus, BrdU influences growth during differentiation to a greater extent than the growth of callus cells. BrdU is effective in halting development when applied 0-24 hours after differentiation induction. An event required for differentiation (the first and second replications) must take place at this time. BrdU action begins with DNA incorporation. The consequent cellular replication becomes slowed and DNA repair results. At the same time RNA and protein levels are similar in BrdU treated and untreated cultures. BrdU thymidine substitution into DNA increases from 28% (2 days) to 68% (3 days) after embryogenic induction. A second BrdU effect follows DNA incorporation. Factors (MIFs) in the medium of BrdU treated cells arrest differentiation. After BrdU is repaired from the DNA, the cells are only able to differentiate after a medium change. Understanding MIF production could explain why some plants differentiate more readily than others. BrdU provides the means for further study of MIF's in the auxin-free inhibition of development.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectPlant tissue culture.en_US
dc.subjectBromodeoxyuridine.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeneticsen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.identifier.proquest8708571en_US
dc.identifier.oclc698258165en_US
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