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Modulation of the hormone setting by Rhodococcus fascians results in ectopic KNOX activation in Arabidopsis

(2008) PLANT PHYSIOLOGY. 146(3). p.1267-1281
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Abstract
The biotrophic actinomycete Rhodococcus fascians has a profound impact on plant development and a common aspect of the symptomatology is the deformation of infected leaves. In Arabidopsis ( Arabidopsis thaliana), the serrated leaf margins formed upon infection resemble the leaf phenotype of transgenic plants with ectopic expression of KNOTTED-like homeobox (KNOX) genes. Through transcript profiling, we demonstrate that class-I KNOX genes are transcribed in symptomatic leaves. Functional analysis revealed that BREVIPEDICELLUS/KNOTTED-LIKE1 and mainly SHOOT MERISTEMLESS were essential for the observed leaf dissection. However, these results also positioned the KNOX genes downstream in the signaling cascade triggered by R. fascians infection. The much faster activation of ARABIDOPSIS RESPONSE REGULATOR5 and the establishment of homeostatic and feedback mechanisms to control cytokinin (CK) levels support the overrepresentation of this hormone in infected plants due to the secretion by the pathogen, thereby placing the CK response high up in the cascade. Hormone measurements show a net decrease of tested CKs, indicating either that secretion by the bacterium and degradation by the plant are in balance, or, as suggested by the strong reaction of 35S:CKX plants, that other CKs are at play. At early time points of the interaction, activation of gibberellin 2-oxidase presumably installs a local hormonal setting favorable for meristematic activity that provokes leaf serrations. The results are discussed in the context of symptom development, evasion of plant defense, and the establishment of a specific niche by R. fascians.
Keywords
CYTOKININ BIOSYNTHESIS, ASYMMETRIC LEAVES1, KNOTTED1-LIKE HOMEOBOX GENE, MERISTEM ACTIVITY, LEAF DEVELOPMENT, CORYNEBACTERIUM-FASCIANS, SHOOT MERISTEMLESS, GIBBERELLIN METABOLISM, PLANT DEVELOPMENT, CELL-DIVISION

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Chicago
Depuydt, Stephen, Karel Doležal, Maria Van Lijsebettens, Thomas Moritz, Marcella Holsters, and Danny Vereecke. 2008. “Modulation of the Hormone Setting by Rhodococcus Fascians Results in Ectopic KNOX Activation in Arabidopsis.” Plant Physiology 146 (3): 1267–1281.
APA
Depuydt, Stephen, Doležal, K., Van Lijsebettens, M., Moritz, T., Holsters, M., & Vereecke, D. (2008). Modulation of the hormone setting by Rhodococcus fascians results in ectopic KNOX activation in Arabidopsis. PLANT PHYSIOLOGY, 146(3), 1267–1281.
Vancouver
1.
Depuydt S, Doležal K, Van Lijsebettens M, Moritz T, Holsters M, Vereecke D. Modulation of the hormone setting by Rhodococcus fascians results in ectopic KNOX activation in Arabidopsis. PLANT PHYSIOLOGY. 2008;146(3):1267–81.
MLA
Depuydt, Stephen, Karel Doležal, Maria Van Lijsebettens, et al. “Modulation of the Hormone Setting by Rhodococcus Fascians Results in Ectopic KNOX Activation in Arabidopsis.” PLANT PHYSIOLOGY 146.3 (2008): 1267–1281. Print.
@article{436432,
  abstract     = {The biotrophic actinomycete Rhodococcus fascians has a profound impact on plant development and a common aspect of the symptomatology is the deformation of infected leaves. In Arabidopsis ( Arabidopsis thaliana), the serrated leaf margins formed upon infection resemble the leaf phenotype of transgenic plants with ectopic expression of KNOTTED-like homeobox (KNOX) genes. Through transcript profiling, we demonstrate that class-I KNOX genes are transcribed in symptomatic leaves. Functional analysis revealed that BREVIPEDICELLUS/KNOTTED-LIKE1 and mainly SHOOT MERISTEMLESS were essential for the observed leaf dissection. However, these results also positioned the KNOX genes downstream in the signaling cascade triggered by R. fascians infection. The much faster activation of ARABIDOPSIS RESPONSE REGULATOR5 and the establishment of homeostatic and feedback mechanisms to control cytokinin (CK) levels support the overrepresentation of this hormone in infected plants due to the secretion by the pathogen, thereby placing the CK response high up in the cascade. Hormone measurements show a net decrease of tested CKs, indicating either that secretion by the bacterium and degradation by the plant are in balance, or, as suggested by the strong reaction of 35S:CKX plants, that other CKs are at play. At early time points of the interaction, activation of gibberellin 2-oxidase presumably installs a local hormonal setting favorable for meristematic activity that provokes leaf serrations. The results are discussed in the context of symptom development, evasion of plant defense, and the establishment of a specific niche by R. fascians.},
  author       = {Depuydt, Stephen and Dole\v{z}al, Karel and Van Lijsebettens, Maria and Moritz, Thomas and Holsters, Marcella and Vereecke, Danny},
  issn         = {0032-0889},
  journal      = {PLANT PHYSIOLOGY},
  keyword      = {CYTOKININ BIOSYNTHESIS,ASYMMETRIC LEAVES1,KNOTTED1-LIKE HOMEOBOX GENE,MERISTEM ACTIVITY,LEAF DEVELOPMENT,CORYNEBACTERIUM-FASCIANS,SHOOT MERISTEMLESS,GIBBERELLIN METABOLISM,PLANT DEVELOPMENT,CELL-DIVISION},
  language     = {eng},
  number       = {3},
  pages        = {1267--1281},
  title        = {Modulation of the hormone setting by Rhodococcus fascians results in ectopic KNOX activation in Arabidopsis},
  url          = {http://dx.doi.org/10.1104/pp.107.113969},
  volume       = {146},
  year         = {2008},
}

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