HISTONE MONOUBIQUITINATION1 interacts with a subunit of the mediator complex and regulates defense against necrotrophic fungal pathogens in Arabidopsis

Plant Cell. 2009 Mar;21(3):1000-19. doi: 10.1105/tpc.108.062364. Epub 2009 Mar 13.


This work examines the role of the Arabidopsis thaliana RING E3 ligase, HISTONE MONOUBIQUITINATION1 (HUB1) in disease resistance. Loss-of-function alleles of HUB1 show increased susceptibility to the necrotrophic fungal pathogens Botrytis cinerea and Alternaria brassicicola, whereas HUB1 overexpression conferred resistance to B. cinerea. By contrast, responses to the bacterial pathogen Pseudomonas syringae are unaltered in hub1 plants. hub1 mutants have thinner cell walls but increased callose around an infection site. HUB1 acts independently of jasmonate, but ethylene (ET) responses and salicylate modulate the resistance of hub1 mutants to necrotrophic fungi. The ET response factor ETHYLENE INSENSITIVE2 is epistatic to HUB1 for A. brassicicola resistance but additive to HUB1 for B. cinerea resistance. HUB1 interacts with MED21, a subunit of the Arabidopsis Mediator, a conserved complex that regulates RNA polymerase II. RNA interference lines with reduced MED21 expression are highly susceptible to A. brassicicola and B. cinerea, whereas T-DNA insertion alleles are embryonic lethal, suggesting an essential role for MED21. However, HUB1-mediated histone H2B modification is independent of histone H3 and DNA methylation. In sum, histone H2B monoubiquitination is an important chromatin modification with regulatory roles in plant defense against necrotrophic fungi most likely through modulation of gene expression.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alternaria / pathogenicity
  • Arabidopsis / anatomy & histology
  • Arabidopsis / microbiology*
  • Arabidopsis / physiology
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Botrytis / pathogenicity
  • DNA Methylation
  • Epistasis, Genetic
  • Gene Expression Regulation, Plant
  • Histones / metabolism
  • Humans
  • Immunity, Innate / physiology*
  • Photoperiod
  • Plant Diseases*
  • Plant Leaves / microbiology
  • Plants, Genetically Modified
  • Protein Subunits / genetics
  • Protein Subunits / metabolism*
  • Pseudomonas syringae / metabolism
  • Pseudomonas syringae / pathogenicity
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Two-Hybrid System Techniques
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*


  • Arabidopsis Proteins
  • COI1 protein, Arabidopsis
  • EIN2 protein, Arabidopsis
  • Histones
  • Protein Subunits
  • Receptors, Cell Surface
  • Transcription Factors
  • HUB1 protein, Arabidopsis
  • Ubiquitin-Protein Ligases