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In vivo inhibition of polyamine biosynthesis and growth in tobacco ovary tissuesPost fertilization growth of tobacco ovary tissues treated with inhibitors of polyamine (PA) biosynthesis was examined in relation to endogenous PA titers and the activities of arginine decarboxylase (ADC, EC 4.1.1.19) and ornithine decarboxylase (ODC, EC 4.1.1.17). DL-alpha-Difluoromethylornithine (DFMO) and DL-alpha-difluoromethylarginine (DFMA), specific, irreversible ("suicide") inhibitors of ODC and ADC in vitro, were used to modulate PA biosynthesis in excised flowers. ODC represented >99% of the total decarboxylase activity in tobacco ovaries. In vivo inhibition of ODC with DFMO resulted in a significant decrease in PA titers, ovary fresh weight and protein content. Simultaneous inhibition of both decarboxylases by DFMO and DFMA produced only a marginally greater depression in growth and PA titers, indicating that ODC activity is rate-limiting for PA biosynthesis in these tissues. Paradoxically, DFMA alone inhibited PA biosynthesis, not as a result of a specific inhibition of ADC, but primarily through the inactivation of ODC. In vivo inhibition of ODC by DFMA appears to result from arginase-mediated hydrolysis of this inhibitor to urea and DFMO, the suicide substrate for ODC. Putrescine conjugates in tobacco appear to function as a storage form of this amine which, upon hydrolysis, may contribute to Put homeostasis during growth.
Document ID
20040089633
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Slocum, R. D.
(Yale University New Haven, CT 06511, United States)
Galston, A. W.
Date Acquired
August 21, 2013
Publication Date
January 1, 1985
Publication Information
Publication: Plant & cell physiology
Volume: 26
Issue: 8
ISSN: 0032-0781
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: 5-RO1-AGO2742
CONTRACT_GRANT: NSG 7290
Distribution Limits
Public
Copyright
Other
Keywords
NASA Program Space Biology
NASA Discipline Plant Biology
NASA Discipline Number 40-10
Non-NASA Center

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