Dhawan Rahul, Luo Hongli, Foerster Andrea Maria, Abuqamar Synan, Du Hai-Ning, Briggs Scott D, Mittelsten Scheid Ortrun, Mengiste Tesfaye
Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907-2054, USA.
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.
这项研究探讨了拟南芥RING E3连接酶组蛋白单泛素化1（HUB1）在抗病性中的作用。HUB1功能缺失等位基因对坏死营养型真菌病原体灰葡萄孢和芸苔链格孢的易感性增加，而HUB1过表达赋予了对灰葡萄孢的抗性。相比之下，hub1植物对细菌病原体丁香假单胞菌的反应未发生改变。hub1突变体的细胞壁更薄，但感染部位周围的胼胝质增加。HUB1的作用独立于茉莉酸，但乙烯（ET）反应和水杨酸调节hub1突变体对坏死营养型真菌的抗性。ET反应因子乙烯不敏感2在对芸苔链格孢的抗性方面对HUB1呈上位性，但在对灰葡萄孢的抗性方面与HUB1呈加性。HUB1与MED21相互作用，MED21是拟南芥中介体的一个亚基，中介体是一种调节RNA聚合酶II的保守复合物。MED21表达降低的RNA干扰株系对芸苔链格孢和灰葡萄孢高度敏感，而T-DNA插入等位基因是胚胎致死的，这表明MED21具有重要作用。然而，HUB1介导的组蛋白H2B修饰独立于组蛋白H3和DNA甲基化。总之，组蛋白H2B单泛素化是一种重要的染色质修饰，在植物抵御坏死营养型真菌的防御中发挥调节作用，很可能是通过调节基因表达来实现的。
