John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
J Cell Sci. 2012 Aug 15;125(Pt 16):3723-31. doi: 10.1242/jcs.084764. Epub 2012 Aug 30.
Growth and development are modulated by environmental signals in many organisms. These signals are often perceived at one stage and 'remembered' until later in development. An increasingly well-understood example of this process in plants is provided by vernalization, which refers to the acquisition of the ability to flower after prolonged exposure to cold. In Arabidopsis thaliana, vernalization involves downregulation and epigenetic silencing of the gene encoding the floral repressor FLOWERING LOCUS C (FLC). This epigenetic silencing is quantitative and increases with the duration of exposure to cold. Vernalization involves a Polycomb-based switching mechanism, with localized nucleation of silencing during periods of cold, and spreading of the silencing complex over the whole gene after the exposure to cold. A number of characteristics of vernalization have recently been elaborated on through the use of mathematical modelling. This has revealed the importance of chromatin dynamics for the switching mechanism and has shown that the quantitative nature of the process is due to cell-autonomous switching of an increasing proportion of cells. The principles derived from vernalization are likely to be widely relevant to epigenetic reprogramming in many organisms.
在许多生物中，环境信号调节着生长和发育。这些信号通常在一个阶段被感知，并“记住”，直到发育的后期。植物中这种过程的一个越来越被充分理解的例子是春化作用，它指的是在长时间暴露于寒冷后获得开花的能力。在拟南芥中，春化作用涉及到花抑制基因 FLOWERING LOCUS C（FLC）的下调和表观遗传沉默。这种表观遗传沉默是定量的，并随着冷暴露时间的增加而增加。春化作用涉及一个基于 Polycomb 的开关机制，在寒冷期间局部形成沉默核，在冷暴露后，沉默复合物在整个基因上扩散。最近，通过使用数学建模，对春化作用的许多特征进行了详细阐述。这揭示了染色质动力学对于开关机制的重要性，并表明该过程的定量性质是由于越来越多的细胞自主开关所致。从春化作用中得出的原则可能广泛适用于许多生物中的表观遗传重编程。
