HISTONE MONOUBIQUITINATION1 Interacts with a Subunit of the Mediator Complex and Regulates Defense against Necrotrophic Fungal Pathogens inArabidopsis 

Abstract

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.

Chitin and chitin-related compounds in plant–fungal interactions

“…For instance, MED14, MED15, MED16 and MED19a have been shown to regulate the SA-triggered immunity against biotrophic and hemibiotrophic pathogens (Canet et al 2012; Zhang et al 2012, 2013; Caillaud et al 2013). MED8, MED12, MED13, MED14, MED16, MED21, MED25 and CDK8 have been found to function in JA/ET-mediated immunity against necrotrophic pathogens (Dhawan et al 2009; Zhang et al 2012). MED18 also operates in resistance to necrotrophic pathogens, but the resistance appears to be independent of the JA/ET signalling (Lai et al 2014).…”

The Mediator Complex in Plants: Structure, Phylogeny, and Expression Profiling of Representative Genes in a Dicot (Arabidopsis) and a Monocot (Rice) during Reproduction and Abiotic Stress

“…approximately 2-fold from S7 to S9 and then staying high in S10; Supplemental Table S10). These seed stages in Arabidopsis correspond to embryo development and cotyledon expansion stages (Schmid et al, 2005), providing credence to the portrayed role of Med21 in embryo development (Dhawan et al, 2009). In rice, on the other hand, the expression of Med21 was 2-fold upregulated in only the P1 stage of panicle development with respect to the vegetative controls, while in seeds, its expression levels remained similar to those in vegetative tissues (Supplemental Tables S4 and S9).…”

“…The study identified STRUW-WELPETER (SWP) as Med14 and PHYTOCHROME AND FLOWERING TIME1 (PFT1) as Med25 subunits. Later, Med21 was shown to interact with HISTONE MONOUBIQUITINATION1 (Dhawan et al, 2009) and the Med12-Med13 pair to regulate pattern formation timing during embryogenesis in Arabidopsis (Gillmor et al, 2010).…”

The Arabidopsis Mediator Complex Subunit16 Is a Key Component of Basal Resistance against the Necrotrophic Fungal Pathogen Sclerotinia sclerotiorum

“…MED14, MED15, MED16, and MED19a have been shown to regulate the SA-triggered immunity against biotrophic and hemibiotrophic pathogens (Canet et al, 2012;Zhang et al, 2012Zhang et al, , 2013Caillaud et al, 2013), whereas MED8, MED12, MED13, MED16, MED21, MED25, and CDK8 have been found to function in JA/ET-mediated immunity against necrotrophic pathogens (Dhawan et al, 2009;Kidd et al, 2009;Zhang et al, 2012;Zhu et al, 2014). MED18 also functions in resistance to necrotrophic pathogens, but the resistance is independent of the JA/ET signaling (Lai et al, 2014).…”