Regulation of (1,3;1,4)-beta-glucan synthesis in the grasses

谷物细胞壁中的非纤维素多糖不会被人体小肠中的酶消化，因此有助于总膳食纤维摄入，这已被证明可以降低严重的人类健康状况的风险，如结肠直肠癌，心血管疾病和II型糖尿病。这些非纤维素细胞壁多糖，特别是称为（1，3; 1，4）-B-葡聚糖（或简称B-葡聚糖）的特定类别在改善健康结果方面的有效性与其在谷物中的水平、其精细结构及其相关的物理化学性质有关。我们先前已经证明大麦B-葡聚糖是由纤维素合成酶样F和纤维素合成酶样H基因家族（CslF和CslH）的成员合成的。这些基因家族的个体成员（即相同基因的不同版本）和/或控制它们何时何地以及在何种水平上打开和关闭的基因的等位基因变异直接或间接地控制它们在谷粒和植物其余部分中的相对丰度和组成（例如分子大小）。事实上，B-葡聚糖含量的变化正是我们在不同的大麦品种中观察到的：我们已经表明，不同的品种含有不同数量的B-葡聚糖，并且观察到的水平受到遗传和环境的控制。一些“极端”的大麦品种含有超过30%的总纤维（参见。糙米3.5%，玉米7%，燕麦10%，小麦12%），并已作为促进健康的超级食品销售（如美国的Sustagrain和澳大利亚的BarleyMax）。这些品种的一个有趣的特点是，它们含有突变的淀粉生物合成途径的组成部分，表明淀粉和β-葡聚糖代谢和积累之间的调节联系。在这个项目中，我们希望精确地研究纤维素合成酶超家族的各个成员，特别是CslF和CslH基因家族成员，是如何被调节的，特别注意那些在谷物发育过程中在谷物中被打开的。这些结果将在大麦育种计划中具有重要的应用，其中低B-葡聚糖对于饲料、麦芽制造和蒸馏工业是重要的，而相反的，即高B-葡聚糖，对于人类健康是可取的。因此，能够利用我们将获得的关于这些基因家族的知识用于未来产品开发的可能性很高（例如，作为降低胆固醇的“健康超级食品”，作为替代增稠剂或新型食品开发，例如小麦面粉的添加剂/替代品）。

Non-cellulosic polysaccharides from cereal grain cell walls are not digested by enzymes in the human small intestine and so contribute to total dietary fibre intake, which has been shown to reduce the risk of serious human health conditions such as colorectal cancer, cardiovascular disease and type II diabetes. The effectiveness of these non-cellulosic cell wall polysaccharides, and in particular a specific class called the (1,3;1,4)-B-glucans (or B-glucans for short), in improving health outcomes is related to their levels in grain, to their fine structure and to their associated physicochemical properties. We have previously shown that barley B-glucans are synthesized by members of the CELLULOSE SYNTHASE-LIKE F and CELLULOSE SYNTHASE LIKE-H gene families (CslF and CslH). Allelic variation at individual members of these gene families (i.e. different versions of the same genes) and/or the genes that control where and when they are switched on and off and at what level, both directly or indirectly control their relative abundance and composition (e.g. molecular size) in both the grain and the rest of the plant. Indeed variation in B-glucan content is precisely what we have observed in different barley cultivars: we have shown that different varieties contain different amounts of B-glucans and that the levels observed are under both genetic and environmental control. Some 'extreme' barley varieties contain more than 30% total fibre (cf. 3.5% in brown rice, 7% in corn, 10% in oats and 12% in wheat) and have been marketed as health promoting super-foods (e.g. Sustagrain in the USA and BarleyMax in Australia). An interesting feature of these varieties is that they contain mutations in components of the starch biosynthetic pathway, suggesting a regulatory link between starch and B-glucan metabolism and accumulation. In this project we want to investigate precisely how individual members of the CELLULOSE SYNTHASE super-family, and in particular CslF and CslH gene family members, are regulated, paying particular attention to those that are switched on in the grain during grain development. The results will have important applications in barley breeding programs where low B-glucan is important for the feed, malting and distilling industries and the opposite, namely high B- glucan, is desirable in the context of human health. The likelihood of being able to exploit the knowledge we will gain about these gene families for future product development is therefore high (e.g. as a cholesterol lowering 'health superfood', as replacement thickening agents or novel food product development such as additives/replacements to wheat based flours).