Chromatin organization in Arabidopsis root epidermal development

一般来说，组成复杂生物体（如植物或动物）的所有不同类型的细胞都具有相同的基因。一个重要但鲜为人知的问题是，如何以不同的方式使用一组基因来产生这些不同类型的细胞。现在出现的一个答案是，基因以半永久性的方式被修改-表观遗传学-这样一些可以被打开，而另一些则不能。因此，不同类型的细胞具有相同的基因，但不同的表观遗传状态，并使用不同的基因子集。重要的问题是这些表观遗传状态是如何建立的，以及在什么程度和什么情况下它们可以改变。对这一点的理解将对生物学和医学产生深远的影响。在动物中，改变表观遗传状态相对困难，这可能是许多动物细胞类型（如大多数神经细胞）无法再生的原因之一。另一方面，植物细胞在发育过程中更加灵活，这就是为什么，例如，植物通常可以从组织碎片（插条）甚至单个细胞再生。我们认为其中一个原因可能在于植物基因组的方式，如染色质（DNA与许多不同的特定蛋白质的复合物）所体现的那样，是表观遗传修饰的。我们已经开始对一种基因进行详细的研究，这种基因负责使植物根部的特定细胞变成根毛细胞。我们已经能够通过先进的显微镜显示，含有该基因的DNA区域在将成为根毛细胞的细胞中处于不同的物理状态，而不是细胞。此外，我们通过观察自然发生的异常细胞表明，这种状态差异是可逆的，并且每次细胞分裂时都可能重置。在这个建议中，我们想研究这个基因中物理差异的详细生化基础。这最终将使我们能够找出基因在不同细胞中处于不同状态的方式和原因，以及这种状态是如何设置和重置的。我们希望这将有助于解释植物细胞如何比动物细胞更容易改变其发育命运。

In general, all the different types of cells that comprise a complex organism like a plant or an animal have the same genes. An important, but little understood, question is how a single set of genes can be used in different ways to produce these different types of cells. One answer that is now emerging is that the genes are modified in semi-permanent ways - epigenetically - so that some can be switched on and others cannot. Thus different types of cells have the same genes, but different epigenetic states, and use different subsets of genes. Important questions are how these epigenetic states are set up and to what extent and under what circumstances they can be changed. An understanding of this will have far-reaching consequences for biology and medicine. In animals, it is relatively difficult to change epigenetic states, which is probably one reason why many animal cell types, such as most nerve cells, cannot be regenerated. On the other hand, plant cells are much more flexible in their development, which is why, for example, plants can often be regenerated from pieces of tissue (cuttings) or even single cells. We think one reason for this is likely to lie in the way plant genomes, as embodied in chromatin (the complex of the DNA with many different specific proteins), are modified epigenetically. We have begun a detailed study of one gene that is responsible for causing specific cells in the root of a plant to become root hair cells. We have been able to show by advanced microscopy that the region of the DNA containing this gene is in a different physical state in cells that will become root hair cells from cells that will not. Furthermore, we have shown by looking at naturally occurring aberrant cells that this difference in state is reversible and is potentially reset every time the cells divide. In this proposal we want to study the detailed biochemical basis of the physical difference in this gene. This should ultimately allow us to find out how and why the genes are in different states in different cells, and how this state is set and reset. We expect that this will help to explain how plant cells can change their developmental fates more easily than animal cells.