• The Plant Pathology Journal
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• 제29권4호
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• pp.364-373
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• 2013

It has been known that most regulation of pathogenicity factor (rpf ) genes in xanthomonads regulates virulence in response to the diffusible signal factor, DSF. Although many rpf genes have been functionally characterized, the function of rpfE is still unknown. We cloned the rpfE gene from a Xanthomonas oryzae pv. oryzae (Xoo) Korean race KACC10859 and generated mutant strains to elucidate the role of RpfE with respect to the rpf system. Through experiments using the rpfE-deficient mutant strain, we found that mutation in rpfE gene in Xoo reduced virulence, swarm motility, and production of virulence factors such as cellulase and extracellular polysaccharide. Disease progress by the rpfE-deficient mutant strain was significantly slowed compared to disease progress by the wild type and the number of the rpfE-deficient mutant strain was lower than that of the wild type in the early phase of infection in the inoculated rice leaf. The rpfE mutant strain was unable to utilize sucrose or xylose as carbon sources efficiently in culture. The mutation in rpfE, however, did not affect DSF synthesis. Our results suggest that the rpfE gene regulates the virulence of Xoo under different nutrient conditions without change of DSF production.

• The Plant Pathology Journal
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• 제24권2호
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• pp.143-151
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• 2008

To define the functions of the rpf genes in Xanthomonas oryzae pv. oryzae (Xoo), which regulates pathogenicity factors in Xanthomonas campestris pv. campestris (Xcc), marker-exchange mutants of each rpf gene were generated. When the mutants were inoculated on a susceptible cultivar, the lesion lengths caused by the rpfB, rpfC, rpfF, and rpfG mutants were significantly smaller than those caused by the wild type, whereas those caused by the rpfA, rpfD, and rpfI mutants were not. Several virulence determinants, including extracellular polysaccharide (EPS) production, xylanase production, and motility, were significantly decreased in the four mutants. However, the cellulase activity in the mutants was unchanged. Complementation of the rpfB and rpfC mutations restored the virulence and the expression of the virulence determinants. Expression analysis of 14 virulence genes revealed that the expression of genes related to EPS production (gumG and gumM), LPS (xanA, xanB, wxoD, and wxoC), phytase (phyA), xylanase (xynB), lipase (lipA), and motility (pitA) were reduced significantly in the mutants rpfB, rpfC, rpfF, and rpfG. In contrast, the expression of genes related to cellulase (eglxob, clsA), cellobiosidase (cbsA), and iron metabolism (fur) was unchanged. The results of this study clearly show that rpfB, rpfC, rpfF, and rpfG are important for the virulence of Xoo KACC10859, and that virulence genes are regulated differently by the Rpfs.

• The Plant Pathology Journal
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• 제27권1호
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• pp.89-92
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• 2011

Cyclic AMP receptor-like protein (Clp), is known to be a global transcriptional regulator for the expression of virulence factors in Xanthomonas campestris pv. campestris (Xcc). Sequence analysis showed that Xanthomonas oryzae pv. oryzae (Xoo) contains a gene that is strongly homologous to the Xcc clp. In order to determine the role of the Clp homolog in Xoo, a marker exchange mutant of $clp_{xoo4158}$ was generated. Virulence and virulence factors, such as the production of cellulase, xylanase, and extracellular polysaccharides (EPS) and swarming motility were significantly decreased in the $clp_{xoo4158}$ mutant. Moreover, the mutation caused the strain to be more sensitive to hydrogen peroxide and to over-produce siderophores. Complementation of the mutant restored the mutation-related phenotypes. Expression of $clp_{xoo4158}$, assessed by reverse-transcription realtime PCR and clp promoter activity, was significantly reduced in the rpfB, rpfF, rpfC, and rpfG mutants. These results suggest that the clp homolog, $clp_{xoo4158}$, is involved in the control of virulence and resistance against oxidative stress, and that expression of the gene is controlled by RpfC and RpfG through a diffusible signal factor (DSF) signal in Xanthomonas oryzae pv. oryzae KACC10859.

• The Plant Pathology Journal
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• 제30권3호
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• pp.304-309
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• 2014

The rpf genes and $colS_{XOO1207}/colR_{XOO1208}$ were known to require for virulence of Xanthomonas oryzae pv. oryzae (Xoo). In Xoo KACC10331 genome, two more colS/colR genes, $colS_{XOO3534}$ (raxH)/$colR_{XOO3535}$ (raxR) and $colS_{XOO3762}/colR_{XOO3763}$ were annotated. The $colS_{XOO3534}/colR_{XOO3535}$ were known to control AvrXa21 activity and functions of $colS_{XOO3762}/colR_{XOO3763}$ were unknown in Xoo. To characterize the relationship between rpf and colS/colR genes, expression of colS/colR genes in Rpf mutants of Xoo were analyzed with quantitative reverse transcription PCR (qRT-PCR). Expressions of all three colS/colR genes increased in the rpfF mutant in which DSF synthesis is defective. Expression of $colS_{XOO1207}/col-R_{XOO1208}$, $colS_{XOO3534}/colR_{XOO3535}$ and $colS_{XOO3762}/colR_{XOO3763}$ increased 2, 2-7, 3-13 folds respectively. Expression of $colS_{XOO3534}$ and $colS_{XOO3762}$ also increased 2-4 folds in the rpfG mutant in which the signal from DSF is no longer transferred to down-stream. Expression of the other colS/colR genes was not significantly changed in the rpfG mutant compared to the wild type. Since RpfF and RpfG are responsible for DSF synthesis and signal transfer from DSF to down-stream to regulate virulence gene expression, these results suggest that the DSF and DSF-mediated signal regulate negatively three colS/colR genes in Xoo.

• The Plant Pathology Journal
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• 제35권1호
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• pp.84-89
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• 2019

Two-component systems (TCSs) are critical to the pathogenesis of Xanthomonas oryzae pv. oryzae (Xoo). We mutated 55 of 62 genes annotated as responsive regulators (RRs) of TCSs in the genome of Xoo strain PXO99A and identified 9 genes involved in Xoo virulence. Four (rpfG, hrpG, stoS, and detR) of the 9 genes were previously reported as key regulators of Xoo virulence and the other 5 have not been characterized. Lesion lengths on rice leaves inoculated with the mutants were shorter than those of the wild type and were significantly restored with gene complementation. The population density of the 5 mutants in planta was smaller than that of PXO99A at 14 days after inoculation, but the growth curves of the mutants in rich medium were similar to those of the wild type. These newly reported RR genes will facilitate studies on the function of TCSs and of the integrated regulation of TCSs for Xoo pathogenesis.

• Tuberculosis and Respiratory Diseases
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• 제55권4호
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• pp.344-352
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• 2003

연구배경 : Isoniazid와 rifampin에 내성인 다제내성 결핵의 유병률은 1995년 세계적으로 5.3%이며 이의 지속적인 증가는 공중보건의 중요한 문제로 대두 되고 있다. 결핵 치료의 중요한 약물의 하나인 RFP에 대한 내성은 불량한 예후를 초래한다. 이에 RFP내성을 조기에 정확하게 진단하는 임상적으로 중요하다. 최근 PCR 방법을 이용하여 약제 (RFP) 내성을 초래하는 변이를 신속하게 진단하는 방법이 가능하게 되었다. 본 연구는 결핵 초치료군, 치료 실패군 및 재발군에서 INNO-LiPA 검사법을 이용하여 RFP내성 유병률을 확인하고 기존의 약제 감수성 검사법을 이용하여 얻은 결과를 비교하여 INNO-LiPA검사의 유용성을 연구하였다. 방 법 : 1998년부터 2002년까지 본원에 내원하여 객담 도말 검사상 양성 소견으로 폐결핵으로 진단받은 46명을 대상으로 하였으며 환자는 초치료, 초치료 실패, 및 재발 환자군으로 분류하였다. RPF 내성은 INNO-LiPA Rif.TB kit을 이용하여 검사하였으며 이를 결핵균 배양을 이용한 약제 감수성 결과와 비교 분석하였다. 결 과 : 46명의 환자중에 21명이 결핵으로 처음 진단받은 환자였으며 17명이 초치료 실패한 환자이었으며 8명이 재발한 환자이었다. 배양 검사를 이용한 약제 감수성 검사법을 기준으로 하여 비교시 INNO-LiPA 검사법을 이용한 RFP 저항성의 양성 예측률은 85.7% 이었으여 음성 예측률은 76.0% 이었다. INNO-LiPA 검사 결과 초치료 실패한 및 재발한 환자 25명의 환자중 20예 (80.0%)에서 rpoB gene의 변이를 보였으며 처음 결핵으로 진단받은 21명의 환자중 4예 (19.0%)에서 rpoB gene의 변이를 보였다. 결 론 : INNO-LiPA 검사는 비교적 신속하고 정확하게 RFP 약제 내성 정보를 제공하여 2차 항결핵 약제의 선택에 도움을 준다. 아울러 기존의 배양 검사를 이용한 약제 감수성 검사법과 함께 상호 보완적으로 사용하면 다제 내성결핵의 치료에 있어 그 유용성은 매우 클 것으로 사료된다.