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RNA silencing is required for Arabidopsis defence against Verticillium wilt disease.

Ellendorff U, Fradin EF, de Jonge R, Thomma BP - J. Exp. Bot. (2008)

Bottom Line: Recently, RNA silencing has been found to play a role in defence against bacterial plant pathogens in Arabidopsis through modulating host defence responses.Several components of RNA silencing pathways were tested, of which many were found to affect Verticillium defence.Since the observed differences in Verticillium susceptibility cannot be explained by notable differences in root architecture, it is speculated that the gene silencing mechanisms affect regulation of Verticillium-specific defence responses.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Phytopathology, Wageningen University, Binnenhaven 5, 6709 PD Wageningen, The Netherlands.

ABSTRACT
RNA silencing is a conserved mechanism in eukaryotes that plays an important role in various biological processes including regulation of gene expression. RNA silencing also plays a role in genome stability and protects plants against invading nucleic acids such as transgenes and viruses. Recently, RNA silencing has been found to play a role in defence against bacterial plant pathogens in Arabidopsis through modulating host defence responses. In this study, it is shown that gene silencing plays a role in plant defence against multicellular microbial pathogens; vascular fungi belonging to the Verticillium genus. Several components of RNA silencing pathways were tested, of which many were found to affect Verticillium defence. Remarkably, no altered defence towards other fungal pathogens that include Alternaria brassicicola, Botrytis cinerea, and Plectosphaerella cucumerina, but also the vascular pathogen Fusarium oxysporum, was recorded. Since the observed differences in Verticillium susceptibility cannot be explained by notable differences in root architecture, it is speculated that the gene silencing mechanisms affect regulation of Verticillium-specific defence responses.

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Related in: MedlinePlus

Arabidopsis sgs mutants display enhanced susceptibility towards Verticillium dahliae. (A) Typical symptoms of V. dahliae on Arabidopsis sgs mutants. The mutants sgs1-1, sgs2-1, sgs3-1, and the corresponding wild type Col-0 were inoculated with V. dahliae strain JR2 or mock-inoculated. V. dahliae-inoculated sgs mutants show enhanced symptom development, including more severe stunting, wilting, anthocyanin accumulation, and tissue necrosis, when compared with Col-0 plants at 19 d post-inoculation. (B) Quantification of symptom development at 19 d post-inoculation shown as a ratio of diseased rosette leaves with standard deviation. The ratio of diseased rosette leaves for Col-0 is set to one. Asterisks indicate significant differences when compared with the wild type Col-0 (P <0.05). (C) Quantitative real-time PCR of fungal colonization by comparing V. dahliae internal transcribed spacer (ITS) transcript levels (as a measure for fungal biomass) relative to Arabidopsis Rubisco transcript levels (for equilibration) at 19 d post-inoculation. The mutants sgs1-1, sgs2-1, sgs3-1, and the corresponding wild type Col-0 were inoculated with V. dahliae strain JR2 and the relative average fungal biomass is shown with standard errors. Asterisks indicate significant differences when compared with colonization of the wild type Col-0.
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fig1: Arabidopsis sgs mutants display enhanced susceptibility towards Verticillium dahliae. (A) Typical symptoms of V. dahliae on Arabidopsis sgs mutants. The mutants sgs1-1, sgs2-1, sgs3-1, and the corresponding wild type Col-0 were inoculated with V. dahliae strain JR2 or mock-inoculated. V. dahliae-inoculated sgs mutants show enhanced symptom development, including more severe stunting, wilting, anthocyanin accumulation, and tissue necrosis, when compared with Col-0 plants at 19 d post-inoculation. (B) Quantification of symptom development at 19 d post-inoculation shown as a ratio of diseased rosette leaves with standard deviation. The ratio of diseased rosette leaves for Col-0 is set to one. Asterisks indicate significant differences when compared with the wild type Col-0 (P <0.05). (C) Quantitative real-time PCR of fungal colonization by comparing V. dahliae internal transcribed spacer (ITS) transcript levels (as a measure for fungal biomass) relative to Arabidopsis Rubisco transcript levels (for equilibration) at 19 d post-inoculation. The mutants sgs1-1, sgs2-1, sgs3-1, and the corresponding wild type Col-0 were inoculated with V. dahliae strain JR2 and the relative average fungal biomass is shown with standard errors. Asterisks indicate significant differences when compared with colonization of the wild type Col-0.

Mentions: Transgenic expression in the post-transcriptional gene silencing (PTGS) mutant suppressor of gene silencing 2 (sgs2; Elmayan et al., 1998; Mourrain et al., 2000) reduces the inter-transformant variability of transgene expression (Butaye et al., 2004). In several experiments to investigate putative defence genes against V. dahliae in Arabidopsis, transgenic overexpression in Col-0 as well as sgs2-1 was performed. Remarkably, in subsequent disease susceptibility assays with V. dahliae strain JR2 it appeared that untransformed sgs2-1 plants displayed more severe disease symptoms than Col-0 plants (Fig. 1A, B). While Col-0 plants displayed only mild disease symptoms upon V. dahliae inoculation as visualized by rather slight stunting resulting in a reduced rosette diameter at 3 weeks post-inoculation, inoculated sgs2-1 plants showed severe stunting, wilting, anthocyanin accumulation, and tissue necrosis (Fig. 1A, B). The ratio of leaves displaying symptoms of disease was also significantly more for sgs2-1 plants than for Col-0 plants (Fig. 1A, B)


RNA silencing is required for Arabidopsis defence against Verticillium wilt disease.

Ellendorff U, Fradin EF, de Jonge R, Thomma BP - J. Exp. Bot. (2008)

Arabidopsis sgs mutants display enhanced susceptibility towards Verticillium dahliae. (A) Typical symptoms of V. dahliae on Arabidopsis sgs mutants. The mutants sgs1-1, sgs2-1, sgs3-1, and the corresponding wild type Col-0 were inoculated with V. dahliae strain JR2 or mock-inoculated. V. dahliae-inoculated sgs mutants show enhanced symptom development, including more severe stunting, wilting, anthocyanin accumulation, and tissue necrosis, when compared with Col-0 plants at 19 d post-inoculation. (B) Quantification of symptom development at 19 d post-inoculation shown as a ratio of diseased rosette leaves with standard deviation. The ratio of diseased rosette leaves for Col-0 is set to one. Asterisks indicate significant differences when compared with the wild type Col-0 (P <0.05). (C) Quantitative real-time PCR of fungal colonization by comparing V. dahliae internal transcribed spacer (ITS) transcript levels (as a measure for fungal biomass) relative to Arabidopsis Rubisco transcript levels (for equilibration) at 19 d post-inoculation. The mutants sgs1-1, sgs2-1, sgs3-1, and the corresponding wild type Col-0 were inoculated with V. dahliae strain JR2 and the relative average fungal biomass is shown with standard errors. Asterisks indicate significant differences when compared with colonization of the wild type Col-0.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2651451&req=5

fig1: Arabidopsis sgs mutants display enhanced susceptibility towards Verticillium dahliae. (A) Typical symptoms of V. dahliae on Arabidopsis sgs mutants. The mutants sgs1-1, sgs2-1, sgs3-1, and the corresponding wild type Col-0 were inoculated with V. dahliae strain JR2 or mock-inoculated. V. dahliae-inoculated sgs mutants show enhanced symptom development, including more severe stunting, wilting, anthocyanin accumulation, and tissue necrosis, when compared with Col-0 plants at 19 d post-inoculation. (B) Quantification of symptom development at 19 d post-inoculation shown as a ratio of diseased rosette leaves with standard deviation. The ratio of diseased rosette leaves for Col-0 is set to one. Asterisks indicate significant differences when compared with the wild type Col-0 (P <0.05). (C) Quantitative real-time PCR of fungal colonization by comparing V. dahliae internal transcribed spacer (ITS) transcript levels (as a measure for fungal biomass) relative to Arabidopsis Rubisco transcript levels (for equilibration) at 19 d post-inoculation. The mutants sgs1-1, sgs2-1, sgs3-1, and the corresponding wild type Col-0 were inoculated with V. dahliae strain JR2 and the relative average fungal biomass is shown with standard errors. Asterisks indicate significant differences when compared with colonization of the wild type Col-0.
Mentions: Transgenic expression in the post-transcriptional gene silencing (PTGS) mutant suppressor of gene silencing 2 (sgs2; Elmayan et al., 1998; Mourrain et al., 2000) reduces the inter-transformant variability of transgene expression (Butaye et al., 2004). In several experiments to investigate putative defence genes against V. dahliae in Arabidopsis, transgenic overexpression in Col-0 as well as sgs2-1 was performed. Remarkably, in subsequent disease susceptibility assays with V. dahliae strain JR2 it appeared that untransformed sgs2-1 plants displayed more severe disease symptoms than Col-0 plants (Fig. 1A, B). While Col-0 plants displayed only mild disease symptoms upon V. dahliae inoculation as visualized by rather slight stunting resulting in a reduced rosette diameter at 3 weeks post-inoculation, inoculated sgs2-1 plants showed severe stunting, wilting, anthocyanin accumulation, and tissue necrosis (Fig. 1A, B). The ratio of leaves displaying symptoms of disease was also significantly more for sgs2-1 plants than for Col-0 plants (Fig. 1A, B)

Bottom Line: Recently, RNA silencing has been found to play a role in defence against bacterial plant pathogens in Arabidopsis through modulating host defence responses.Several components of RNA silencing pathways were tested, of which many were found to affect Verticillium defence.Since the observed differences in Verticillium susceptibility cannot be explained by notable differences in root architecture, it is speculated that the gene silencing mechanisms affect regulation of Verticillium-specific defence responses.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Phytopathology, Wageningen University, Binnenhaven 5, 6709 PD Wageningen, The Netherlands.

ABSTRACT
RNA silencing is a conserved mechanism in eukaryotes that plays an important role in various biological processes including regulation of gene expression. RNA silencing also plays a role in genome stability and protects plants against invading nucleic acids such as transgenes and viruses. Recently, RNA silencing has been found to play a role in defence against bacterial plant pathogens in Arabidopsis through modulating host defence responses. In this study, it is shown that gene silencing plays a role in plant defence against multicellular microbial pathogens; vascular fungi belonging to the Verticillium genus. Several components of RNA silencing pathways were tested, of which many were found to affect Verticillium defence. Remarkably, no altered defence towards other fungal pathogens that include Alternaria brassicicola, Botrytis cinerea, and Plectosphaerella cucumerina, but also the vascular pathogen Fusarium oxysporum, was recorded. Since the observed differences in Verticillium susceptibility cannot be explained by notable differences in root architecture, it is speculated that the gene silencing mechanisms affect regulation of Verticillium-specific defence responses.

Show MeSH
Related in: MedlinePlus