| 1. |
- Asari, Shashidar, et al.
(författare)
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Analysis of plant growth-promoting properties of Bacillus amyloliquefaciens UCMB5113 using Arabidopsis thaliana as host plant
- 2017
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Ingår i: Planta. - : Springer Science and Business Media LLC. - 0032-0935 .- 1432-2048. ; 245, s. 15-30
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Tidskriftsartikel (refereegranskat)abstract
- This study showed that Bacillus amyloliquefaciens UCMB5113 colonizing Arabidopsis roots changed root structure and promoted growth implying the usability of this strain as a novel tool to support sustainable crop production.Root architecture plays a crucial role for plants to ensure uptake of water, minerals and nutrients and to provide anchorage in the soil. The root is a dynamic structure with plastic growth and branching depending on the continuous integration of internal and environmental factors. The rhizosphere contains a complex microbiota, where some microbes can colonize plant roots and support growth and stress tolerance. Here, we report that the rhizobacterium Bacillus amyloliquefaciens subsp. plantarum UCMB5113 stimulated the growth of Arabidopsis thaliana Col-0 by increased lateral root outgrowth and elongation and root-hair formation, although primary root elongation was inhibited. In addition, the growth of the above ground tissues was stimulated by UCMB5113. Specific hormone reporter gene lines were tested which suggested a role for at least auxin and cytokinin signaling during rhizobacterial modulation of Arabidopsis root architecture. UCMB5113 produced cytokinins and indole-3-acetic acid, and the formation of the latter was stimulated by root exudates and tryptophan. The plant growth promotion effect by UCMB5113 did not appear to depend on jasmonic acid in contrast to the disease suppression effect in plants. UCMB5113 exudates inhibited primary root growth, while a semi-purified lipopeptide fraction did not and resulted in the overall growth promotion indicating an interplay of many different bacterial compounds that affect the root growth of the host plant. This study illustrates that beneficial microbes interact with plants in root development via classic and novel signals.
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| 2. |
- Asari, Shashidar, et al.
(författare)
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Insights into the molecular basis of biocontrol of Brassica pathogens by Bacillus amyloliquefaciens UCMB5113 lipopeptides
- 2017
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Ingår i: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 120, s. 551-562
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Tidskriftsartikel (refereegranskat)abstract
- Background and Aims Certain micro-organisms can improve plant protection against pathogens. The protective effect may be direct, e.g. due to antibiotic compounds, or indirect, by priming of plant defence as induced systemic resistance (ISR). The plant growth-promoting rhizobacterium Bacillus amyloliquefaciens UCMB5113 shows potential for disease management of oilseed rape. To investigate the mode of action of this protection, especially in relation to jasmonic acid-dependent ISR, Bacillus UCMB5113 was tested with Arabidopsis thaliana mutants and several important fungal pathogens of Brassica species.Methods Secreted lipopeptide fractions from Bacillus UCMB5113, together with synthetic peptide mimics, were evaluated for their effects on fungal phytopathogens and A. thaliana. The structures of secreted lipopeptides were analysed using mass spectrometry. Plant mutants and reporter lines were used to identify signalling steps involved in disease suppression by lipopeptides.Key Results In plate tests Bacillus UCMB5113 and lipopeptide extracts suppressed growth of several fungal pathogens infecting Brassica plants. Separation of secreted lipopeptides using reversed-phase high-performance liquid chromatography revealed several fractions that inhibited fungal growth. Analysis by mass spectrometry identified the most potent compounds as novel linear forms of antifungal fengycins, with synthetic peptide mimics confirming the biological activity. Application of the lipopeptide extracts on Arabidopsis roots provided systemic protection against Alternaria brassicicola on leaves. Arabidopsis signalling mutants and PDF1.2 and VSP2 promoter-driven GUS lines indicated that the lipopeptide fraction involved jasmonic-acid-dependent host responses for suppression of fungal growth indicative of ISR.Conclusions The ability of Bacillus UCMB5113 to counteract pathogens using both antagonistic lipopeptides and through ISR provides a promising tool for sustainable crop production.
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| 3. |
- Asari, Shashidar, et al.
(författare)
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Multiple effects of Bacillus amyloliquefaciens volatile compounds: plant growth promotion and growth inhibition of phytopathogens
- 2016
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 0168-6496 .- 1574-6941. ; 92
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Tidskriftsartikel (refereegranskat)abstract
- Biotic interactions through volatile organic compounds (VOC) are frequent in nature. This investigation aimed to study the role of Bacillus VOC for the beneficial effects on plants observed as improved growth and pathogen control. Four Bacillus amyloliquefaciens subsp. plantarum strains were screened for VOC effects on Arabidopsis thaliana Col-0 seedlings and Brassica fungal phytopathogens. VOC from all four Bacillus strains could promote growth of Arabidopsis plants resulting in increased shoot biomass but the effects were dependent on the growth medium. Dose response studies with UCMB5113 on MS agar with or without root exudates showed significant plant growth promotion even at low levels of bacteria. Bacillus VOC antagonized growth of several fungal pathogens in vitro. However, the plant growth promotion efficacy and fungal inhibition potency varied among the Bacillus strains. VOC inhibition of several phytopathogens indicated efficient microbial antagonism supporting high rhizosphere competence of the Bacillus strains. GC-MS analysis identified several VOC structures where the profiles differed depending on the growth medium. The ability of Bacillus strains to produce both volatile and soluble compounds for plant growth promotion and disease biocontrol provides examples of rhizosphere microbes as an important ecosystem service with high potential to support sustainable crop production.
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| 4. |
- Asari, Shashidar
(författare)
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Studies on plant-microbe interaction to improve stress tolerance in plants for sustainable agriculture
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biotic and abiotic stress factors have a major impact on plants and cause extensive losses to crop production. Bacteria that provide growth promotion and prime stress tolerance of plants have great potential to improve crop production and support durable and environmental friendly resource management. Priming refers here to when plants upon appropriate stimulation develop an enhanced capacity to express defense responses to a later stimulus. In this study strains of the beneficial bacterium Bacillus amyloliquefaciens were analysed for their effects on plants. Direct antagonistic effect of B. amyloliquefaciens on several Brassica phytopathogens (Botrytis cinerea, Alternaria brassicae, Alternaria brassicicola, Verticillium longisporum, and Sclerotinia sclerotiorum) was demonstrated by bacteria and exudates in vitro. A bacterial exudate fraction containing lipopeptide antibiotics was analysed and the strongest antagonistic activity was connected with a novel linear form of fengycin identified using mass spectrometry. Growth promotion of Arabidopsis thaliana Col-0, coi1-16, jar1 and npr1 but not in myb72 plants by B. amyloliquefaciens UCMB5113 was demonstrated with increased shoot and root biomass and increased number of lateral roots and root hairs while the primary root growth decreased. Bacillus inoculation resulted in profound effects on various plant hormones that will affect a variety of plant functions. Growth promotion was also demonstrated in split dish experiments where Bacillus strains were sequestered from Arabidopsis plants indicating a role for volatile organic compounds (VOCs). Bacillus VOCs also caused growth suppression of several phytopathogens. GC-MS analysis identified a large number of compounds in the VOC blend and the composition of VOCs was dependent on the medium used for cultivation and the effects on the plant also varied. Thus these Bacillus strains promote growth of plants and improve the survivability of plants exposed to biotic stress challenges by priming of stress tolerance. These findings can be extended to different crops to improve crop productivity under various environmental conditions.
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| 5. |
- Niazi, Adnan, et al.
(författare)
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Genome Analysis of Bacillus amyloliquefaciens Subsp. plantarum UCMB5113: A Rhizobacterium That Improves Plant Growth and Stress Management
- 2014
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The Bacillus amyloliquefaciens subsp. plantarum strain UCMB5113 is a Gram-positive rhizobacterium that can colonize plant roots and stimulate plant growth and defense based on unknown mechanisms. This reinforcement of plants may provide protection to various forms of biotic and abiotic stress. To determine the genetic traits involved in the mechanism of plantbacteria association, the genome sequence of UCMB5113 was obtained by assembling paired-end Illumina reads. The assembled chromosome of 3,889,532 bp was predicted to encode 3,656 proteins. Genes that potentially contribute to plant growth promotion such as indole-3-acetic acid (IAA) biosynthesis, acetoin synthesis and siderophore production were identified. Moreover, annotation identified putative genes responsible for non-ribosomal synthesis of secondary metabolites and genes supporting environment fitness of UCMB5113 including drug and metal resistance. A large number of genes encoding a diverse set of secretory proteins, enzymes of primary and secondary metabolism and carbohydrate active enzymes were found which reflect a high capacity to degrade various rhizosphere macromolecules. Additionally, many predicted membrane transporters provides the bacterium with efficient uptake capabilities of several nutrients. Although, UCMB5113 has the possibility to produce antibiotics and biosurfactants, the protective effect of plants to pathogens seems to be indirect and due to priming of plant induced systemic resistance. The availability of the genome enables identification of genes and their function underpinning beneficial interactions of UCMB5113 with plants.
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