The function and specificity of Golgi sugar nucleotide transporters in cell wall synthesis

植物细胞被坚硬的细胞壁包围。由一系列不同类型的糖组成的长链被称为多糖，是植物细胞壁的主要成分。不同的植物细胞和组织的性质在很大程度上是由于壁多糖的不同而不同。例如，随着水果的成熟和软化，作为粘合剂将细胞粘合在一起的多糖果胶开始分解。细胞壁多糖在我们的饮食中非常重要，作为膳食纤维，它可以保护我们免受癌症和其他疾病的侵袭。通过形成攻击生物的屏障的一部分，多糖也参与了植物对疾病的抗性。然而，我们不知道每一种特定的多糖成分对植物或我们饮食的重要性。如果我们能培育出具有不同多糖结构的植物，我们就可以研究它们对我们和植物的重要性。高尔基体是一种在每个细胞内制造多糖的结构。单个糖单位通过高尔基体的膜传递给制造长链多糖的酶。为了做到这一点，有大量的转运蛋白将糖带过细胞膜。我们最近发现了四个基因，它们指导着四个这样的转运蛋白的合成，我们称之为GONSTs。我们想研究缺失这些基因的突变植物，以了解每个转运蛋白对植物的重要性。我们预计这些突变植物将不能产生所有正常的多糖，但我们不知道确切地说哪些多糖会受到影响。我们也不知道改变细胞壁会给植物带来什么后果。我们已经拥有的关于一个突变体的数据告诉我们，果胶的合成将受到影响。这将意味着植物不能正常生长。当我们进行了这项研究后，我们将知道一些壁多糖的结构在实验室中可以如何改变。我们最终应该能够培育出壁上含有变化的多糖的农作物，从而带来饮食、工业和农业方面的好处。

Plant cells are surrounded by rigid cell walls. Long chains made of a range of different types of sugars, known as polysaccharides, are major components of plant cell walls. Different plant cells and tissues vary in their properties largely due to differences in the wall polysaccharides. For example, as fruits ripen and soften, the polysaccharide pectin which functions as a glue holding cells together begins to be broken down. Cell walls polysaccharides are very important in our diet, as dietary fibre, and protect us against cancer and other diseases. By forming part of the barrier to attacking organisms, polysaccharides are also involved in plant resistance to diseases. However, we do not know the importance to the plant or to our diet of each particular polysaccharide component. If we could breed plants with different polysaccharide structures, we could investigate their importance to us and the plant. The Golgi apparatus is a structure that makes the polysaccharides within each cell. Individual sugar units are delivered to the enzymes making the long chain polysaccharides through the membrane of the Golgi apparatus. To do this, there are a large number of transporter proteins that take the sugars across the membrane. We have recently discovered four genes that direct the synthesis of four of these transporters, which we call GONSTs. We would like to study mutant plants missing each of these genes, to understand what the importance of each transporter is to the plant. We expect that these mutant plants will not be able to make all the normal polysaccharides, but we do not know precisely which polysaccharides will be affected. We also do not know what the consequences for the plant will be of having changed cell walls. Data we already have on one mutant tells us to expect that pectin synthesis will be affected. This will mean that the plant does not grow normally. When we have carried out this study, we will know how the structure of some of the wall polysaccharides can be changed in the laboratory. We should eventually be able to breed crop plants with changed polysaccharides in their wall, bringing dietary, industrial and agricultural benefits.