Chan Zhulong, Wang Yanping, Cao Minjie, Gong Yuehua, Mu Zixin, Wang Haiqing, Hu Yuanlei, Deng Xin, He Xin-Jian, Zhu Jian-Kang
Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, Hubei Province, 430074, China.
Shanghai Center for Plant Stress Biology and Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China.
New Phytol. 2016 Mar;209(4):1527-39. doi: 10.1111/nph.13727. Epub 2015 Nov 2.
The C-REPEAT-BINDING FACTOR (CBF) pathway has important roles in plant responses to cold stress. How the CBF genes themselves are activated after cold acclimation remains poorly understood. In this study, we characterized cold tolerance of null mutant of RNA-DIRECTED DNA METHYLATION 4 (RDM4), which encodes a protein that associates with RNA polymerases Pol V and Pol II, and is required for RNA-directed DNA methylation (RdDM) in Arabidopsis. The results showed that dysfunction of RDM4 reduced cold tolerance, as evidenced by decreased survival and increased electrolyte leakage. Mutation of RDM4 resulted in extensive transcriptomic reprogramming. CBFs and CBF regulon genes were down-regulated in rdm4 but not nrpe1 (the largest subunit of PolV) mutants, suggesting that the role of RDM4 in cold stress responses is independent of the RdDM pathway. Overexpression of RDM4 constitutively increased the expression of CBFs and regulon genes and decreased cold-induced membrane injury. A great proportion of genes affected by rdm4 overlapped with those affected by CBFs. Chromatin immunoprecipitation results suggested that RDM4 is important for Pol II occupancy at the promoters of CBF2 and CBF3. We present evidence of a considerable role for RDM4 in regulating gene expression at low temperature, including the CBF pathway in Arabidopsis.
C-重复结合因子（CBF）途径在植物对低温胁迫的响应中发挥着重要作用。低温驯化后CBF基因自身如何被激活仍知之甚少。在本研究中，我们对RNA定向DNA甲基化4（RDM4）基因敲除突变体的耐寒性进行了表征，RDM4编码一种与RNA聚合酶Pol V和Pol II相关的蛋白质，是拟南芥中RNA定向DNA甲基化（RdDM）所必需的。结果表明，RDM4功能失调降低了耐寒性，这可通过存活率降低和电解质渗漏增加得到证明。RDM4突变导致广泛的转录组重编程。CBF及其调控子基因在rdm4突变体中下调，但在nrpe1（Pol V的最大亚基）突变体中未下调，这表明RDM4在低温胁迫响应中的作用独立于RdDM途径。RDM4的过表达持续增加CBF及其调控子基因的表达，并减少低温诱导的膜损伤。受rdm4影响的很大一部分基因与受CBF影响的基因重叠。染色质免疫沉淀结果表明，RDM4对Pol II结合到CBF2和CBF3启动子上很重要。我们提供了证据，证明RDM4在调节低温下的基因表达中发挥着重要作用，包括拟南芥中的CBF途径。
