• Journal of Plant Biotechnology
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• v.44 no.2
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• pp.149-155
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• 2017

Bacterial blight in rice caused by Xanthomonas oryzae pv. oryzae (Xoo) greatly reduces the growth and productivity of this important food crop. Therefore, we sought to increase the resistance of rice to bacterial blight by using a NAC (NAM, ATAF, and CUC) transcription factor, one of the plant-specific transcription factors that is known to be involved in biotic/abiotic stress resistance. By isolating the OsNAC58 gene from rice and analyzing its biological functions related to Xoo resistance, phylogenetic analysis showed that OsNAC58 belongs to group III. To investigate the biological relationship between bacterial leaf blight (BLB) and OsNAC58 in rice, we constructed a vector for overexpression in rice and generated transgenic rice. The expression analysis resulting from use of RT-PCR showed that OsNAC58-overexpressed transgenic rice exhibited higher levels of OsNAC58 expression than wild types. Further, subcellular localization analysis using rice protoplasts showed that the 35S/OsNAC58-SmGFP fusion protein was localized in the nuclei. Thirteen OsNAC58-overexpressed transgenic rice lines, with high expression levels of OsNAC58, showed more resistant to Xoo than did the wild types. Together, these results suggest that the OsNAC58 gene of rice regulates the rice disease resistance mechanism in the nucleus upon invasion of the rice bacterial blight pathogen Xoo.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.2
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• pp.162-168
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• 2007

Compatible and incompatible interactions of near-isogenic lines containing one of Xa1, Xa3, and Xa7 resistance genes with Japanese bacterial blight isolates (T7174, T7147, and T7133) were examined in order to determine the variation of bacterial blight resistance and the stability of resistance gene. IRBB 101 line having a Xal gene was compatible (host susceptible) with T7147 and T7133 isolates but incompatible (host resistant) with T7174 isolate at all the tested rice growth stages. IRBB 103 line having a Xa3 gene was susceptible or moderately resistant to the three isolates at seedling and maximum tillering stage but resistant at heading stage. IRBB 101 line having a Xa7 gene was semi-compatible with the three isolates at seedling stage but incompatible at the other growth stages. Overall there were clear differences between compatible and incompatible interactions of rice with Xanthomonas oryzae pv. oryzae races. In the mixed inoculations of compatible and incompatible isolates, the lesion length from near-isogenic lines decreased as the ratios of incompatible races increased. When the distinction between compatible and incompatible isolates was unclear, there was almost no variation of lesion length regardless of mixed ratios. The pathogenicity of the mixed races in the incompatible Interactions increased rather than the individual inoculation whereas the lesion length of compatible interactions was similar to that of the individual inoculation. These data indicate the incompatible races inhibit the virulence of a compatible race but compatible races increase the disease occurrence due to incompatible races. Furthermore, IRBB 107 line that showed resistance to all the isolates at all the tested growth stages was considered as a good parent f3r breeding of resistant variety.

• Microbiology and Biotechnology Letters
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• v.40 no.1
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• pp.39-42
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• 2012

A new method for the high throughput screening of antagonistic substances against rice pathogens using rice leaf explants was developed. This method can be used to confirm the activities of any compound or mixture suppressing rice bacterial blight (BB) before field tests. Xanthomonas oryzae pv. oryzae (Xoo) culture medium was distributed in 96 well plates with equally sized explants and the active compounds were added to the wells. The strength suppressing BB was converted into an area percent of the lesion on the rice explants. The explants under BB suppressing activity remained uninfected maintaining their actual green color, while infected explants exhibited pale yellow-colored lesions. Based on the results, this method seems to be faster and easier, dose-dependent, and can be performed all-at-once with a small amount of unspecified compounds. This method also has the potential to be applied to inspection activities for the suppression of other waterborne crop diseases.

• Korean Journal of Environmental Agriculture
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• v.16 no.4
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• pp.347-355
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• 1997

For the selection of plants contained pesticidal active conpounds, 31 families 59 species of native plants were collected and biological activites of their crude extracts against brown planthopper (Nilaparvata lugens), Xanthomonas oryzae pv. oryzae and allelopathy were examined. Among the screened plants, the crude extracts from the leaves of Ricinus communis and Sophora angustifolia showed 100% and 82% of mortality on brown planthopper at the concentration of 1% (w/v) respectively. Mixed crude extracts of Sophora angustifolia root and Melia azedarach seed exhibited 128${\sim}$155% of synergistic effects on the mortality of brown planthopper. In case of fungicidal activity, the crude extracts from the leaves of 8 plants including Chrysanthemum indicum were inhibitory of the growth of Xanthomonas oryzae pv. oryzae at 1%(w/v) soluction. Seed germination of radish (Raphanus sativas) and barnyardgrass (Echinochloa crus-galli) was inhibited by 0.5%(w/v) leaf extracts of Pinus densiflora and Quercus acutissima. MeOH extracts of Pinus denislora leaves gave 100% inhibition in seed germintion of radish at 2%(w/v) soluction and showed a complete inhibition in seedling growth of barnyardgrass as well as radish at 5% solution.

• Korean journal of applied entomology
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• v.18 no.2 s.39
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• pp.77-84
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• 1979

Ten isolates of Xanthomonas oryzae were inoculated to three rice varieties; 'Milyang 23' in Kinmaze group, 'Yushin' in Kogyoku group and 'Tongil' in Rantai-emas group, at the seedling stage, early-tillering stage, Maximum-tillering stage and flag-leaf stage. Much fluctuation was existed in virulence pattern of isolates at each growth stage. Especially, the isolates of pathotype II showed much more variation in virulence. This suggests that there would be more sub-divided pathotypes involved in pathotype II. Isolate G 7716 of pathotype II showed its virulence to 'Yushin' variety only after booting stage. On the result of the analysis of variance for the reaction of three rice varieties to three isolates at each growth stage; the isolates, varieties, growth stages were the main factors of variations of virulence, and the interaction of isolates with varieties was significant but other interactions were not.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2004.10a
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• pp.65-67
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• 2004

During initial interactions of bacteria with their host plants, most plants recognize the bacterial infections and repel the pathogen by plant defense mechanism. The most active plant defense mechanism is the hypersensitive response (HR) which is the localized induced cell death in the plant at the site of infection by a pathogen. A primary locus induced in gram-negative phytopathogenic bacteria during this initial interaction is the Hrp locus. The Hrp locus is composed of a cluster of genes that encodes the bacteral Type 111 machinery that is involved in the secretion and translocation of effector proteins to the plant cell. DNA sequence analysis of hrp gene in phytopathogenic bacteria has revealed a Hrp pathogenicity is]and (PAI) with a tripartite mosaic structure. For many gram-negative pathogenic bacteria, colonization of the host's tissue depends on the type III protein secretion system (TTSS) which secrets and translocates effector proteins into the host cell. Effectors can be divided into several groups including broad host range effectors, host specific effectors, disease specific effectors, and effectors inhibit host defenses. The role of effectors carrying LRR domain in plant resistance is very elusive since most known plant resistance gene carry LRR domain. Host specific effectors such as several avr gene products are involved in the determination of the host specificity. Almost all the phytopathogenic Xanthomonas spp. carry avrBs1, avrBs2, and avrBs3 homologs. Some strains of X. oryzae pv. oryzae carry more than 10 copies of avrBs3 homologs. However, the functions of all those avr genes in host specificity are not characterized well.;

• Journal of Microbiology and Biotechnology
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• v.24 no.9
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• pp.1269-1279
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• 2014

Xanthomonas oryzae pv. oryzae (Xoo) strains are plant pathogenic bacteria that can cause serious blight of rice, and their virulence towards plant host is complex, making it difficult to be elucidated. Caenorhabditis elegans has been used as a powerful model organism to simplify the host and pathogen system. However, whether the C. elegans is feasible for studying plant pathogens such as Xoo has not been explored. In the present work, we report that Xoo strains PXO99 and JXOIII reduce the lifespan of worms not through acute toxicity, but in an infectious manner; pathogens proliferate and persist in the intestinal lumen to cause marked anterior intestine distension. In addition, Xoo triggers (i) the p38 MAPK signal pathway to upregulate its downstream C17H12.8 expression, and (ii) the DAF-2/DAF-16 pathway to upregulate its downstream gene expressions of mtl-1 and sod-3 under the condition of daf-2 mutation. Our findings suggest that C. elegans can be used as a model to evaluate the virulence of Xoo phytopathogens to host.

• Korean journal of applied entomology
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• v.4
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• pp.29-32
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• 1965

1. The 30 isolates of Xanthomonas oryzae collected from various places in Korea were classified into 2 strains in A' and B, by the 4 kinds of Japanese bacteriophages as follow; A' strain; Susceptible to $OP_1$ and $OP_2$ but not to $OP_1h$ and $OP_1h_2$. B strain; Susceptible to $OP_1h$, $OP_1h_2$ and $OP_2$ but not to $OP_1$. Of these bacterial strains, A' strain, a little different to A strain in Japan, was susceptible to $OP_1h_2$, while A' strain was resistant to $OP_1h_2$, 2. A' strain was widely and commonly distributed throughout this country, In geographical distribution, it was generally known that A' strain was distributed in south of Kyunggi-Do, whereas B strain was distributed north of Suwon area. 3. No specific tendency was found in the distribution of these strains in same variety.

• Korean journal of applied entomology
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• v.23 no.3 s.60
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• pp.147-152
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• 1984

Six hundred and twenty five isolates of Xanthomonas campestris pv. oryzae, cauing bacterial leaf blight (BLB) of rice, were classified into five pathotypes during $1979\~1983$ in Korea. Among them, 483 isolates$(77.3\%)$ were classified as pathotype I, 83 $(13.3\%)$ as pathotype II, 54$(8.6\%)$ as pathotype III, 3 $(0.5\%)$ as pathotype IV and 2$(0.3\%)$ as pathotype V. Pathotype I was the most prevalent throughout the country. Pathotype III was widely distributed in the western or southern parts of Korea, particularly in Jeonnam, Chungnam and Gyeongnam provinces. One isolate of pathotype IV was found in Gyeongnam in 1980, and two isolates were found in Jeonnam in 1981. Most of the isolates were obtained from Milyang 23 varietal group, while the isolates of pathotype III were collected from Yushin and Tongil varietal group.

• Korean journal of applied entomology
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• v.17 no.1 s.34
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• pp.15-22
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• 1978

The study has been carried out to investigate the mechanism of 'Kresek' induction caused by Xanthomonas oryzae (Uyeda & Ishiyama) Dowson. The results are summarized as follows: 1. K-isolate could always induce 'Kresek' symptom on susceptible varieties when the pathogenic bacteria were introduced either way through the leaves or roots, while N-isolate could not induce. 2. Milyang 23 which showed 'Kresek' symptom had significantly smaller diameter of vessel elements than those of other two varieties examined. 3. The bacterial number of It-isolates in the extract of Milyang 23 was higher than N-isolates but there was no difference in bacterial number between K-and N-isolates when they were grown in the extract of Tongil. 4. N and K-isolates reached to death phase after 3 days and 9 days, respectibly, when they were grown in the extract of Milyang 23. Both isolates, however, reached to death phase at the same time after 3 days of incubation in the extract of Tonsil. 5. Heavy precipitation was observed in the extract of Milyang 23 at PH 3.0-4.0 range, while only traceable precipitation could be observed in the extract of Tongil at the same pH range under room temperature.