• The Plant Pathology Journal
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• 제15권1호
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• pp.21-27
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• 1999

Nonpathogenic mutants of Xanthomonas campestris pv. glycines were generated with Omegon-Kim to isolate genes essential for pathogenicity and inducing hypersensitive response (HR). Three nonpathogenic multants and two mutants showing slow symptom development were isolated among 1,000 colonies tested. From two nonpathogenic mutants, 8-13 and 26-13, genes homologous to hrcC and hrpF of X. campestris pv. vesicatoria were identified. The nonpathogenic mutant 8-13 had a mutation in a gene homologous to hrpF of X. campestris pv. vesicatoria and failed to cause HR on pepper plants but still induced HR on tomato leaves. The nonpathogenic mutant 26-13 had an insertional mutation in a gene homologous to hrcC of X. campestris pv. vesicatoria and lost the ability to induce HR on pepper leaves but still caused HR on tomato plants. Unlike other phytopathogenic bacteria, the parent strain and these two mutants of X. campestris pv. glycines did not cause HR on tobacco plants. a cosmid clone, pBL1, that complemented the phenotypes of 8-13 was isolated. From the analysis of restriction enzyme mapping and deletion analyses of pBL1, a 9.0-kb Eco RI fragment restored the phenotypes of 8-13. pBL1 failed to complement the phenotypes of 26-13, indicating that the hrcC gene resides outside of the insert DNA of pBL1. One nonpathogenic mutant, 13-33, had a mutation in a gene homologous to a miaA gene encoding tRNA delta (2)-isopentenylpyrophosphate transferase of Escherichia coli. This indicated that tRNA modifications in X. campestris pv. glycines may be required for expression of genes necessary for pathogenicity. The mutant 13-33 multiplied as well as the parent strain did in the culture medium and in planta, indicating that loss of pathogenicity is not due to the inability of multiplication in vivo.

• 한국식물병리학회지
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• 제13권3호
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• pp.179-183
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• 1997

십자화과 식물에 검은썩음병을 일으키는 Xanthomonas campestris pv. campestris에 대하여 담배 18품종 중 가장 과민반응을 강하게 나타내는 품종(Nicotiana tabacum cv. TC500)을 과민반응 비기주식물로 선발하였다. NTG 돌연변이를 실시하여 얻은 약 4,500개의 mutant들을 $10^{8}$ cells/ml의 농도로 주사 접종하여 비기주식물인 담배 잎에서 과민반응을 유도하지 않는 HR-mutans(XHN 514-774, XHN 620-831)를 선발하였고, 기주식물인 양배추 잎에서 병원성을 나타내지 않는 비병원성변이주(XPN 1001)를 선발하였다. HR mutant를 기주식물인 양배추에 접종한 결과 병원성을 나타내었고, nonpathogenic mutant를 비기주식물인 담배잎에 접종한 결과 과민반응을 유도하였다. 담배 잎에서 HR-mutant와 wild type의 population를 조사한 결과 wild type은 24시간 이후 급격히 감소하는 반면, HR mutant는 일정수준을 유지하였으나 72시간 이후에 감소하였다. 그리고 mutant들의 protease, cellulase, amylase, polygalacturonate lyase 분비여부를 조사한 결과 wild type과 비슷하게 분비하였다.

• 한국식물병리학회지
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• 제14권2호
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• pp.145-149
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• 1998

Four nonpathogenic isolates of Fusarium oxysporum isolated from spinach showed suppressive effect on the occurrence of the Fusarium wilt of spinach caused by F. oxysporum f. sp. sprinaciae, among which NF01 controlled the disease most effectively. And NF01 was not pathogenic to tomato, cucumber, radish and spinach. This isolate was further tested for the biological control of the disease. The isolate was not inhibitory to the growth of the pathogen on potato sucrose agar medium, however the Fusarium wilt disease occurred less by drenching spore suspension of the nonpathogenic isolate. The control effect of the isolate was higher at lower inoculum level of the pathogen than at the higher inoculum level, and in the pretreatments than the simultaneous treatment of the isolate with the pathogen inoculation. The nit mutants of the isolate were easily formed on chlorate containing media, and was reisolated selectively as nit mutant from infected soil and plants. The reisolation rate of the isolate as opposed to pathogen was high at preinoculated soil and plants relative to the simultaneous inoculation of the isolate with the pathogen.

• 식물병연구
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• 제16권2호
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• pp.136-140
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• 2010

Pectobacterium carotovorum subsp. carotovorum은 채소 무름병의 원인균이다. 박테리오신인 carocin D는 Pectobacterium carotovorum subsp. Carotovorum Pcc21 균주가 생산한다. Pcc21 균주의 비병원성인 돌연변이주를 선발하기 위해 Tn5을 이용하여 무작위적 삽입 돌연변이체들을 대상으로 병원성 검사를 하였다. 실험 결과 선발된 P. carotovorum subsp. carotovorum Pcc21-M15과 carocin D 유전자의 형질전환체인 E. coli(pRG3431)은 비병원성인 동시에 carocin D를 생산하여 무름병균인 P. carotovorum subsp. carotovorum Pcc3의 생장을 억제함을 확인하였다. Pcc21-M15와 E. coli (pRG3431)를 무름병균인 P. carotovorum subsp. carotovorum Pcc3과 함께 미네랄 오일법으로 상추에 처리한 결과 Pcc3 균주를 단독 처리했을 경우에는 3일만에 90%가 무름병에 걸린 반면, Pcc21-M15와 E. coli(pRG3431)를 함께 처리한 경우는 6일 후에도 25%의 상추에서만 무름병 증상을 보였다.

• Journal of Microbiology and Biotechnology
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• 제11권6호
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• pp.1061-1065
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• 2001

The antibacterial effects of water extracts of Scutellariate Radix (a dried root of Scutellaria baicalensis GEORGI) and its major flavonoid components, Baicalin and Baicalein, on Salmonella typhimurium, a representative enteric pathogen, were studied. Through a Kriby-Bauer disc analysis, the growth-inhibition activity of Scutellariae Radix against. S. typhimurium was found to be compatible with commercial antibiotics, such as ampicillin, chloramphenicol, and streptomycin. In contrast, the growth of a nonpathogenic E. coli strain was unaffercted by Scutellariae Radix. To examine the effect of polyphosphate kinase (ppk), a putative virulence factor, on the antibacterial activity of Scutellariae Radix, the growth profile of a ppk mutant of S. typhimurium was investigated in a tryptic soy broth containing different concentrations of water extracts of Scutellariae Radix. The ppk mutant was able to grow in 6 mg/ml of water extracts of Scutellariae Radix, whereas in 6 mg/ml of water extracts of Scutellariae Radix, whereas the wild-type could not, implying that the inactivation of ppk made S. typhimurium more resistant to the antibacterial activity of Scutellariae Radix. No enhanced resistance was observed in a ppk mutant of S. typhimurium complemented with a ppk expression vector. The attenuation of the virulence by ppk inactivation was also observed in a virulence assay using BLAB/c mice. Neither Baicalin nor Baicalein exhibited any growth-inhibition activity against S. typhimurium. The water extracts of Scutellariae Radix stimulated the transcription of ppk, especially in the early growth-stage of S. typhimurium.

• The Plant Pathology Journal
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• 제26권1호
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• pp.8-16
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• 2010

The phytopathogenic fungus Magnaporthe oryzae is a major limiting factor in rice production. To understand the genetic basis of M. oryzae pathogenic development, we previously analyzed a library of T-DNA insertional mutants of M. oryzae, and identified ATMT0879A1 as one of the pathogenicity-defective mutants. Molecular analyses and database searches revealed that a single TDNA insertion in ATMT0879A1 resulted in functional interference with an annotated gene, MGG00056, which encodes a short-chain dehydrogenase/reductase (SDR). The mutant and annotated gene were designated as $MoSDR1^{T-DNA}$ and MoSDR1, respectively. Like other SDR family members, MoSDR1 possesses both a cofactor-binding motif and a catalytic site. The expression pattern of MoSDR1 suggests that the gene is associated with pathogenicity and plays an important role in M. oryzae development. To understand the roles of MoSDR1, the deletion mutant ${\Delta}Mosdr1$ for the gene was obtained via homology-dependent gene replacement. As expected, ${\Delta}Mosdr1$ was nonpathogenic; moreover, the mutant displayed pleiotropic defects in conidiation, conidial germination, appressorium formation, penetration, and growth inside host tissues. These results suggest that MoSDR1 functions as a key metabolic enzyme in the regulation of development and pathogenicity in M. oryzae.