The role of acylation in cellulose synthesis

纤维素是许多植物细胞壁的主要成分，被认为是世界上最丰富的天然聚合物。纤维素实际上是由许多链的糖（葡萄糖）单元结合在一起形成一种被称为微纤维的东西。这些微原纤维具有被植物利用的独特物理特性。纤维素微原纤维在高等植物中普遍存在，它们在决定植物细胞如何生长和植物材料的强度方面起着重要作用。我们已经利用纤维素的特性来制造纸张和棉花，然而，纤维素有潜力被广泛应用于其他领域，包括新材料，以及作为生产生物燃料和化学品的可再生糖源。使用植物基材料的一个主要优点是植物以二氧化碳的形式从大气中获取碳，因此使用植物材料（如纤维素）不仅是可再生的，而且与使用化石燃料相比，大大减少了向大气中的净碳排放。纤维素是由一种独特的酶复合物合成的，这种酶复合物位于包围每个细胞内容物的质膜中。每个纤维素合成酶复合物会产生大约18条链，这些链结合在一起形成微纤维。这些微原纤维是刚性结构，因此当复合物在生长链上添加糖时，它就能有效地沿着质膜移动。考虑到复合物的大尺寸，它会导致质膜的严重局部破坏。质膜由脂质组成，脂质为纤维素合酶复合物的运动提供了一个流体环境，但细胞维持质膜的完整性对其生存能力至关重要。纤维素合酶复合物的运动是由被称为微管的长管状结构控制的，微管靠近质膜，引导纤维素合酶复合物的运动，从而引导纤维素微原纤维的方向。纤维素微原纤维的取向对植物细胞的生长至关重要，并对其物理性质有重要影响。尽管纤维素非常丰富，但研究纤维素存在一些技术挑战，包括将其与细胞壁的其他部分分离，以及打破其强键结构。令人惊讶的是，纤维素的巨大重要性与我们对其形成背后过程的理解并不匹配。我们对纤维素合酶复合体的单个组分是如何通过添加脂肪酸基团来修饰的产生了兴趣。这些脂肪酸基团是非常疏水的，对膜有非常高的亲和力。我们认为，这在将纤维素合酶复合物锁定在质膜中并防止其在复合物穿过膜时“弹出”方面发挥了重要作用。细胞还面临着另一个后勤问题，因为质膜上挤满了许多其他成分。我们现在想看看质膜是如何分裂的，以允许纤维素合酶复合物的畅通无阻的运动。我们将研究疏水脂肪酸基团在纤维素合成酶复合物和底层微管上的添加如何促进它们的共定位和细胞在纤维素合成位点形成膜分区的能力。最终，这项工作应该提供一个框架，我们可以用它来改变它产生的纤维素的性质。我们已经知道，一些突变会降低纤维素的结晶度，从而使其更容易分解为可用于生物燃料或其他工业应用的组成糖。很可能，更好地了解植物制造纤维素的当地环境可能有助于我们改变纤维素的其他特性，如微纤维长度。

Cellulose is the major component of many plant cells walls and is considered to be the world's most abundant naturally occurring polymer. Cellulose is actually composed on many chains of the sugar (glucose) units bonded together to form something known as the microfibril. These microfibrils have unique physical properties that are exploited by plants. Cellulose microfibrils are ubiquitous among higher plants where they are important in determining how plant cells grow and also determining how strong the plant material is. We already exploit the properties of cellulose to make paper and cotton, however, cellulose has the potential to be used in a wide range of other applications including novel materials and as a renewable source of sugars for the production of biofuels and chemicals. One of the major advantages of using plant based material is that plants obtain their carbon from the atmosphere in form of CO2 and so using plant material such as cellulose is not only renewable, but dramatically reduces net carbon emission into the atmosphere compared to the use of fossil fuels. Cellulose is synthesis by a unique enzyme complex that sits in the plasma membrane that surrounds the contents of every cell. Each cellulose synthase complex makes around 18 chains that bond together to form a microfibril. These microfibrils are rigid structures and so as the complex adds sugars to the growing chains, it is effectively driven along the plasma membrane. Given the large size of the complex, it will cause severe local disruption of the plasma membrane. The plasma membrane is composed of lipids that provide a fluid environment that allows movement of the cellulose synthase complex, but it is essential the cells maintain the integrity of the plasma membrane for its viability. Movement of the cellulose synthase complex is governed by long tubular structures known as microtubules that sit close to the plasma membrane and guide the movement of cellulose synthase complex and hence orientation of the cellulose microfibrils. Orientation of cellulose microfibrils is essential for the growth of plant cells and has a major influence on their physical properties.Although cellulose is very abundant, there are several technological challenges associated with studying cellulose, including separating it from other parts of the cell wall and breaking up its strongly bonded structure. Surprisingly, the vast importance of cellulose is not matched by our understanding of the processes behind its formation. We have become interested in how the individual components of the cellulose synthase complex are modified by the addition of fatty acid groups. These fatty acid groups are very hydrophobic and have a very high affinity for membranes. We believe this has an essential role in locking the cellulose synthase complex into the plasma membrane and preventing it "popping out" as the complex moves through the membrane. The cells are also faced with another logistical problem, as the plasma membrane is crowded with many other components. We now want to look at how the plasma membrane might be partitioned to allow unimpeded movement of the cellulose synthase complex. We will investigate how the addition of hydrophobic fatty acid groups both to the cellulose synthase complex and to the underlying microtubules contributes their co-localisation and the ability of the cell to form membrane partitions at sites of cellulose synthesis.Ultimately this work should provide a framework that we can use to make changes that may alter the properties of the cellulose that it produces. It is already known that some mutations reduce the crystalinity of the cellulose and so make it easier to breakdown into its constituent sugars that maybe used for biofuels or other industrial applications. It is likely that a better understanding of the local environment in which plants make cellulose may help us to alter other cellulose properties such as microfibril length.