A pathogenicity locus of Pseudomonas syringae pv.
syringae identified by Tn5 mutagenesis was investigated.
The mutant strain PS9024 is attenuated for disease
expression in its host, Phaseolus vulgaris, but produces
the hypersensitive reaction (HR) in the nonhost, tobacco
(Nicotina tabacum). A cosmid clone carrying 16 kilobases
(kb) of contiguous genomic DNA partially complements this
mutant. Altered growth of the mutant in planta was also
partially restored. Marker exchange mutagenesis with Tn3-
HoHo1 at two other sites within this locus results in
mutants with attenuated and severely reduced
pathogenicity. The locus is complex and contains
repetitive DNA sequences. Northern analysis reveals that
this locus is expressed in planta, but is not expressed in
a rich growth medium, and the transcript is larger than 10
kb, suggesting that the locus is transcribed as a
polycistronic mRNA. Comparison of total cellular protein
profiles of R32 and PS9024 using SDS-PAGE analysis further
reveals that at least nine protein bands ranging from
approximately 100 kD or above in size are present in the
wild type strain R32, but absent from the mutant.
Additionally, a protein of approximately 45 kD is absent
from the mutant. The site of Tn5 insertion has been
partially sequenced. The initial search of the data banks
suggested a gene or genes related to the ornithine
biosynthetic pathway map to this locus. Further study
strongly suggest a gene that encodes a membranceassociated
protein and under the control of a promoter
identical to appA gene promoter maps at this site and it
is involved in the process of pathogenesis. / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37468 |
| Date | 03 May 1991 |
| Creators | Zhao, Yuqi |
| Contributors | Mills, Dallice |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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