| Summary: | 碩士 === 中臺科技大學 === 醫學生物科技研究所 === 96 === Xanthomonas campestris pv. campestris (Xcc) is the causal agent
of black rot in cruciferous plants. Xcc produces exopolysaccharide (EPS)
and various extracellular enzymes, such as a-amylase, pectate lyase,
endoglucanase and proteases, which are collectively essential for
pathogenesis. Pathogenicity of Xcc is regulated by rpf gene cluster (for
regulation of pathogenicity factors). Previous studies have shown that
production of these virulence factors is positive regulated by rpf gene
cluster. The amino acid sequence of RpfF has highly identity to
enoyl-CoA hydratase and is demonstrated directly leading DSF synthesis.
DSF regulate various virulence factors synthesis by signal transduction.
Twelve protein spots difference was found by 2D-PAGE which was
compared between wild type and P20H(rpfF::Gm), rpfF mutant obtained
in previous study. The number 5 protein spot was identified as XCC3400
(DsbA) (ATCC33913 strain) which is periplasmic thiol: disulfide
oxidoreducatase by LC/MS/MS. XCC3399, upstream gene of XCC3400,
also belong to DsbA family. We named those two genes as dsbA1 and
dsbA2 to make XCC3400 and XCC3399 could be distinguishable. Serial
experiments were carried out for understanding how RpfF regulate dsbA1
and dsbA2, and whether DsbA1 and DsbA2 influence the Xcc virulence
by catalyses folding of various factors. The results of above-mentioned
study: (1) Mutation in dsbA1 or dsbC abolish ability of virulence, but
mutation in dsbA2 shows no difference with wild type. (2) Secretion of
protease slightly decreases while mutate in dsbA1 or dsbC, but decreases
while mutate of dsbA1 and dsbC. (3) The deletion of dsbA1 and dsbC
brings filamentous phage fLf resistibility to host, while mutation in
dsbA2 is no effect. (4) Swimming motility abolish when mutation in
5
dsbA1 and dsbC. (5)We suppose possible inferences about the assay of
transcription expression: the transcription of dsbA1 is upregulated by
RpfF and fliC is indirectly upregulated by DsbA1 and DsbA2;
transcription of pilA1 is not regulated by DsbA1 and DsbA2, these two
genes probably effect on protein folding.
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