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Rice-Infecting Pseudomonas Genomes Are Highly Accessorized and Harbor Multiple Putative Virulence Mechanisms to Cause Sheath Brown Rot.

Quibod IL, Grande G, Oreiro EG, Borja FN, Dossa GS, Mauleon R, Cruz CV, Oliva R - PLoS ONE (2015)

Bottom Line: Among the rice-infecting Pseudomonas, P. fuscovaginae has been associated with sheath brown rot disease in several rice growing areas around the world.Transcript accumulation of putative pathogenicity-related genes during rice colonization revealed a concerted virulence mechanism.The study suggests that rice-infecting Pseudomonas causing sheath brown rot are intrinsically diverse and maintain a variable set of metabolic capabilities as a potential strategy to occupy a range of environments.

View Article: PubMed Central - PubMed

Affiliation: Plant Breeding, Genetics, and Biotechnology Division, International Rice Research Institute, Los Baños, Philippines.

ABSTRACT
Sheath rot complex and seed discoloration in rice involve a number of pathogenic bacteria that cannot be associated with distinctive symptoms. These pathogens can easily travel on asymptomatic seeds and therefore represent a threat to rice cropping systems. Among the rice-infecting Pseudomonas, P. fuscovaginae has been associated with sheath brown rot disease in several rice growing areas around the world. The appearance of a similar Pseudomonas population, which here we named P. fuscovaginae-like, represents a perfect opportunity to understand common genomic features that can explain the infection mechanism in rice. We showed that the novel population is indeed closely related to P. fuscovaginae. A comparative genomics approach on eight rice-infecting Pseudomonas revealed heterogeneous genomes and a high number of strain-specific genes. The genomes of P. fuscovaginae-like harbor four secretion systems (Type I, II, III, and VI) and other important pathogenicity machinery that could probably facilitate rice colonization. We identified 123 core secreted proteins, most of which have strong signatures of positive selection suggesting functional adaptation. Transcript accumulation of putative pathogenicity-related genes during rice colonization revealed a concerted virulence mechanism. The study suggests that rice-infecting Pseudomonas causing sheath brown rot are intrinsically diverse and maintain a variable set of metabolic capabilities as a potential strategy to occupy a range of environments.

No MeSH data available.


Related in: MedlinePlus

Infection caused by P. fuscovaginae-like strain IRRI 7007 in O. sativa cv. Azucena.A) Plants were inoculated at 45 days after transplanting using toothpick method. B) Symptom development along the sheath showing brown necrotic lesions. C) Discolored inner sheath. D) Poorly emerged panicles with brown to dark brown grains. E) Emerged panicles with discolored grains and progressive necrotic stripes at maturity stage.
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pone.0139256.g001: Infection caused by P. fuscovaginae-like strain IRRI 7007 in O. sativa cv. Azucena.A) Plants were inoculated at 45 days after transplanting using toothpick method. B) Symptom development along the sheath showing brown necrotic lesions. C) Discolored inner sheath. D) Poorly emerged panicles with brown to dark brown grains. E) Emerged panicles with discolored grains and progressive necrotic stripes at maturity stage.

Mentions: To reproduce sheath brown rot and grain discoloration symptoms produced by Pfv-like pathogens, we inoculated the rice cultivars Azucena and Moroberekan using the toothpick method (Fig 1A). Phenotypic symptoms caused by the three Pfv-like strains were similar to Pfv as reported in Asia, Africa, and South America [6, 7, 16] which include the appearance of brown to reddish brown discolorations extending to the entire length of the sheath to its inner tissues (Fig 1B and 1C). Similar to the findings made by Cottyn et al. [22], Pfv-like strains were pathogenic on rice and showed variation in virulence spectrum. In order to validate pathogen spread, plants were kept until maturity to assess phenotypic symptoms in the grain. In most cases, panicles that emerged from the inoculated plants were necrotic and produced discolored grains that are often sterile compared with the control plants (Fig 1D and 1E). Fluorescent Pseudomonas colonies similar to Pfv were re-isolated from the infected sheath (data not shown). In addition to previous findings [22], these observations indicate that Pfv-like populations represented by IRRI 6609, IRRI 7007, and S-E1 harbor similar capabilities as that of Pfv to infect the rice host. Although sheath brown rot and seed discoloration phenotype assessment was not the aim of this study, we found that all strains were able to spread successfully across different tissues. Therefore, we decided to investigate the composition of Pfv-like factors contributing to bacterial sheath brown rot at the genomic level.


Rice-Infecting Pseudomonas Genomes Are Highly Accessorized and Harbor Multiple Putative Virulence Mechanisms to Cause Sheath Brown Rot.

Quibod IL, Grande G, Oreiro EG, Borja FN, Dossa GS, Mauleon R, Cruz CV, Oliva R - PLoS ONE (2015)

Infection caused by P. fuscovaginae-like strain IRRI 7007 in O. sativa cv. Azucena.A) Plants were inoculated at 45 days after transplanting using toothpick method. B) Symptom development along the sheath showing brown necrotic lesions. C) Discolored inner sheath. D) Poorly emerged panicles with brown to dark brown grains. E) Emerged panicles with discolored grains and progressive necrotic stripes at maturity stage.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4589537&req=5

pone.0139256.g001: Infection caused by P. fuscovaginae-like strain IRRI 7007 in O. sativa cv. Azucena.A) Plants were inoculated at 45 days after transplanting using toothpick method. B) Symptom development along the sheath showing brown necrotic lesions. C) Discolored inner sheath. D) Poorly emerged panicles with brown to dark brown grains. E) Emerged panicles with discolored grains and progressive necrotic stripes at maturity stage.
Mentions: To reproduce sheath brown rot and grain discoloration symptoms produced by Pfv-like pathogens, we inoculated the rice cultivars Azucena and Moroberekan using the toothpick method (Fig 1A). Phenotypic symptoms caused by the three Pfv-like strains were similar to Pfv as reported in Asia, Africa, and South America [6, 7, 16] which include the appearance of brown to reddish brown discolorations extending to the entire length of the sheath to its inner tissues (Fig 1B and 1C). Similar to the findings made by Cottyn et al. [22], Pfv-like strains were pathogenic on rice and showed variation in virulence spectrum. In order to validate pathogen spread, plants were kept until maturity to assess phenotypic symptoms in the grain. In most cases, panicles that emerged from the inoculated plants were necrotic and produced discolored grains that are often sterile compared with the control plants (Fig 1D and 1E). Fluorescent Pseudomonas colonies similar to Pfv were re-isolated from the infected sheath (data not shown). In addition to previous findings [22], these observations indicate that Pfv-like populations represented by IRRI 6609, IRRI 7007, and S-E1 harbor similar capabilities as that of Pfv to infect the rice host. Although sheath brown rot and seed discoloration phenotype assessment was not the aim of this study, we found that all strains were able to spread successfully across different tissues. Therefore, we decided to investigate the composition of Pfv-like factors contributing to bacterial sheath brown rot at the genomic level.

Bottom Line: Among the rice-infecting Pseudomonas, P. fuscovaginae has been associated with sheath brown rot disease in several rice growing areas around the world.Transcript accumulation of putative pathogenicity-related genes during rice colonization revealed a concerted virulence mechanism.The study suggests that rice-infecting Pseudomonas causing sheath brown rot are intrinsically diverse and maintain a variable set of metabolic capabilities as a potential strategy to occupy a range of environments.

View Article: PubMed Central - PubMed

Affiliation: Plant Breeding, Genetics, and Biotechnology Division, International Rice Research Institute, Los Baños, Philippines.

ABSTRACT
Sheath rot complex and seed discoloration in rice involve a number of pathogenic bacteria that cannot be associated with distinctive symptoms. These pathogens can easily travel on asymptomatic seeds and therefore represent a threat to rice cropping systems. Among the rice-infecting Pseudomonas, P. fuscovaginae has been associated with sheath brown rot disease in several rice growing areas around the world. The appearance of a similar Pseudomonas population, which here we named P. fuscovaginae-like, represents a perfect opportunity to understand common genomic features that can explain the infection mechanism in rice. We showed that the novel population is indeed closely related to P. fuscovaginae. A comparative genomics approach on eight rice-infecting Pseudomonas revealed heterogeneous genomes and a high number of strain-specific genes. The genomes of P. fuscovaginae-like harbor four secretion systems (Type I, II, III, and VI) and other important pathogenicity machinery that could probably facilitate rice colonization. We identified 123 core secreted proteins, most of which have strong signatures of positive selection suggesting functional adaptation. Transcript accumulation of putative pathogenicity-related genes during rice colonization revealed a concerted virulence mechanism. The study suggests that rice-infecting Pseudomonas causing sheath brown rot are intrinsically diverse and maintain a variable set of metabolic capabilities as a potential strategy to occupy a range of environments.

No MeSH data available.


Related in: MedlinePlus