Arabidopsis thaliana: a powerful model organism to explore histone modifications and their upstream regulations

Histones are subjected to extensive covalent modifications that affect inter-nucleosomal interactions as well as alter chromatin structure and DNA accessibility. Through switching the corresponding histone modifications, the level of transcription and diverse downstream biological processes can be regulated. Although animal systems are widely used in studying histone modifications, the signalling processes that occur outside the nucleus prior to histone modifications have not been well understood due to the limitations including non viable mutants, partial lethality, and infertility of survivors. Here, we review the benefits of using Arabidopsis thaliana as the model organism to study histone modifications and their upstream regulations. Similarities among histones and key histone modifiers such as the Polycomb group (PcG) and Trithorax group (TrxG) in Drosophila, Human, and Arabidopsis are examined. Furthermore, prolonged cold-induced vernalization system has been well-studied and revealed the relationship between the controllable environment input (duration of vernalization), its chromatin modifications of FLOWERING LOCUS C (FLC), following gene expression, and the corresponding phenotypes. Such evidence suggests that research on Arabidopsis can bring insights into incomplete signalling pathways outside of the histone box, which can be achieved through viable reverse genetic screenings based on the phenotypes instead of direct monitoring of histone modifications among individual mutants. The potential upstream regulators in Arabidopsis can provide cues or directions for animal research based on the similarities between them.组蛋白(histones)会经历广泛的共价修饰，这类修饰既能影响核小体间的相互作用，也可改变染色质结构与DNA可及性。通过调控对应组蛋白修饰的状态，可对转录水平及多种下游生物学过程进行精准调控。尽管动物模型被广泛应用于组蛋白修饰的相关研究，但由于存在突变体无法存活、部分个体致死、存活个体不育等局限，组蛋白修饰发生前细胞核外的信号传导过程尚未得到充分阐释。本文综述了以拟南芥(Arabidopsis thaliana)作为模式生物，开展组蛋白修饰及其上游调控机制研究的诸多优势。本文还分析了果蝇(Drosophila)、人类与拟南芥中，组蛋白及多梳蛋白家族(Polycomb group, PcG)、三胸蛋白家族(Trithorax group, TrxG)等关键组蛋白修饰因子之间的保守相似性。此外，长期低温诱导的春化(vernalization)系统已得到充分研究，该系统阐明了可调控的环境输入因子（春化时长）、开花位点C(FLOWERING LOCUS C, FLC)的染色质修饰、后续基因表达与对应表型之间的关联。上述研究证据表明，针对拟南芥的研究可为组蛋白调控通路之外尚未阐明的信号传导通路提供新视角，而这类研究可通过基于表型的可存活反向遗传筛选实现，无需对单个突变体的组蛋白修饰进行直接检测。基于动植物之间的保守相似性，拟南芥中潜在的上游调控因子可为动物相关研究提供研究线索与方向。