The Mediator subunit SFR6/MED16 controls defence gene expression mediated by salicylic acid and jasmonate responsive pathways

Authors

  • Deepthi L. Wathugala,

    1. Durham Centre for Crop Improvement Technology, School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK
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  • Piers A. Hemsley,

    1. Durham Centre for Crop Improvement Technology, School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK
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  • Caroline S. Moffat,

    1. Durham Centre for Crop Improvement Technology, School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK
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  • Pieter Cremelie,

    1. Durham Centre for Crop Improvement Technology, School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK
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  • Marc R. Knight,

    1. Durham Centre for Crop Improvement Technology, School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK
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  • Heather Knight

    1. Durham Centre for Crop Improvement Technology, School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK
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Author for correspondence:
Marc R. Knight
Tel: +44 191 334 1224
Email: m.r.knight@durham.ac.uk

Summary

  • Arabidopsis SENSITIVE TO FREEZING6 (SFR6) controls cold- and drought-inducible gene expression and freezing- and osmotic-stress tolerance. Its identification as a component of the MEDIATOR transcriptional co-activator complex led us to address its involvement in other transcriptional responses.
  • Gene expression responses to Pseudomonas syringae, ultraviolet-C (UV-C) irradiation, salicylic acid (SA) and jasmonic acid (JA) were investigated in three sfr6 mutant alleles by quantitative real-time PCR and susceptibility to UV-C irradiation and Pseudomonas infection were assessed.
  • sfr6 mutants were more susceptible to both Pseudomonas syringae infection and UV-C irradiation. They exhibited correspondingly weaker PR (pathogenesis-related) gene expression than wild-type Arabidopsis following these treatments or after direct application of SA, involved in response to both UV-C and Pseudomonas infection. Other genes, however, were induced normally in the mutants by these treatments. sfr6 mutants were severely defective in expression of plant defensin genes in response to JA; ectopic expression of defensin genes was provoked in wild-type but not sfr6 by overexpression of ERF5.
  • SFR6/MED16 controls both SA- and JA-mediated defence gene expression and is necessary for tolerance of Pseudomonas syringae infection and UV-C irradiation. It is not, however, a universal regulator of stress gene transcription and is likely to mediate transcriptional activation of specific regulons only.

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