Physical, genetic, and biochemical analyses of mannityl opine catabolism genes from the Agrobacterium Ti plasmid pTi15955
Hong, Seung-Beom
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https://hdl.handle.net/2142/21098
Description
Title
Physical, genetic, and biochemical analyses of mannityl opine catabolism genes from the Agrobacterium Ti plasmid pTi15955
Author(s)
Hong, Seung-Beom
Issue Date
1994
Doctoral Committee Chair(s)
Farrand, Stephen K.
Department of Study
Crop Sciences
Discipline
Crop Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Biology, Genetics
Biology, Microbiology
Language
eng
Abstract
We have isolated and characterized Tn3HoHo1- and Tn5-induced mutants of a cosmid clone, pYDH208, which encodes the mannopine cyclase-associated catabolism of mannopine (MOP) and agropine (AGR). Characterization of the transposon-induced lacZ fusion mutants by $\beta$-galactosidase activity and mannityl opine utilization patterns identified at least six genetic units associated with catabolism of these opines. Functions for catabolism of MOP and mannopinic acid (MOA) are encoded by a 16.4 kb region, whereas those for AGR are encoded by a 9.4 kb region located within the MOP catabolic locus. The induction pattern of catabolism shown by transposon insertion derivatives suggests that catabolism of MOP, AGR and MOA encoded by pYDH208 is regulated by at least two independent control elements. Kinetic uptake assays indicated that the clone encodes two transport systems for MOP and AGR, one constitutive and slow, and the other inducible and rapid. Analysis of $\beta$-galactosidase activities from lacZ reporter gene fusions indicated that expression of mannityl opine catabolic genes is not strongly repressed by sugars but is repressed by succinate when ammonium is the nitrogen source. Repression exerted by succinate was relieved when MOP was supplied as sole source of nitrogen. This suggests that genes for opine catabolism encoded by pYDH208 are regulated in part by nitrogen availability.
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