Files in this item



application/pdf9712359.pdf (4MB)Restricted to U of Illinois
(no description provided)PDF


Title:Characterization of genes involved in tabtoxinine-beta-lactam and lysine biosynthesis by Pseudomonas syringae pv. tabaci strain PTBR2.024
Author(s):Liu, Lixia
Doctoral Committee Chair(s):Shaw, Paul D.
Department / Program:Crop Sciences
Discipline:Crop Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Biology, Molecular
Biology, Microbiology
Abstract:The relationship between the biosynthesis of tabtoxinine-$\beta$-lactam $\rm(T\beta L)$ and lysine by Pseudomonas syringae pv. tabaci strain BR2.024 (PTBR2.024) was investigated. A Tn5 mutant of PTBR2.024 showing diaminopimelate auxotrophy and $\rm T\beta L$-deficiency was isolated. Complementation results indicate that a region containing single open reading frame (ORF) is able to complement both mutant phenotypes. The deduced amino acid sequence of the ORF has a significant sequence homology to known dapB gene products, a lysine biosynthetic enzyme of bacteria. Furthermore, the ORF is able to complement an E. coli dapB mutant. The ORF was designated dapB. These results suggest that L-2,3,4,5-tetrahydrodipicolinate is a common intermediate in lysine and $\rm T\beta L$ biosynthesis.
A gene with a predicted product having an amino acid sequence homologous to known dapD gene products, another lysine biosynthetic enzyme in bacteria, was also identified. Complementation tests, in vitro transcription/translation analysis and enzymatic assays indicate that the dapD-like gene is able to encode a product with THDPA N-succinyltransferase (THDPA-ST) activity in E. coli. However, no THDPA-ST activity was detected in PTBR2.024 and a mutation in the dapD-like gene has no effect on lysine biosynthesis of strain PTBR2.024. These results indicate that the dapD-like gene is not involved in lysine biosynthesis in PTBR2.024. The mutation, however, caused a 50 percent reduction in $\rm T\beta L$ production. This suggests that the dapD-like gene may be involved in $\rm T\beta L$ biosynthesis. The dapD-like gene was named tabB.
Enzymatic assay results indicate that PTBR2.024 uses an acetyl pathway for lysine biosynthesis. This is the first report of a Gram-negative bacterium utilizing that pathway.
An gene, ORF$\rm\sb{L}$, able to complement the dapD mutant $\beta$274 also was isolated from the PTBR2.024 genomic library. A mutant with an insertion in ORF$\rm\sb{L}$ produced as much T$\beta$L as parent strain. However, the mutant had reduced growth rate in minimal medium. The growth rate was restored by addition of lysine in minimal medium. Complementation analyses indicate that the ORF$\rm\sb{L}$ mutant phenotype was due to a polar effect. This suggests that the ORF$\rm\sb{L}$ may not be involved in either lysine or tabtoxin biosynthesis.
Issue Date:1996
Rights Information:Copyright 1996 Liu, Lixia
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9712359
OCLC Identifier:(UMI)AAI9712359

This item appears in the following Collection(s)

Item Statistics