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

来自谷物细胞壁的非纤维素多糖不被人类小肠中的酶消化，因此有助于总的膳食纤维摄入量，这已被证明可以降低患严重人类健康疾病的风险，如结直肠癌、心血管疾病和II型糖尿病。这些非纤维素细胞壁多糖，特别是一种被称为(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它们在谷物中的水平、它们的精细结构和相关的物理化学性质有关。我们以前已经证明大麦B-葡聚糖是由纤维素合成酶样F和纤维素合成酶样H基因家族的成员(CslF和CslH)合成的。这些基因家族个别成员的等位基因变异(即相同基因的不同版本)和/或控制它们在哪里、何时开关以及处于什么水平的基因，都直接或间接地控制它们在籽粒和植物其余部分中的相对丰度和组成(如分子大小)。事实上，β-葡聚糖含量的差异正是我们在不同大麦品种中观察到的：我们已经表明，不同品种含有不同数量的β-葡聚糖，观察到的水平受到遗传和环境的控制。一些‘极端’大麦品种的总纤维含量超过30%(参见粗米含3.5%，玉米含7%，燕麦含10%，小麦含12%)，并被作为促进健康的超级食品销售(例如美国的Sustagrain和澳大利亚的BARLEYMAX)。这些品种的一个有趣的特征是，它们在淀粉生物合成途径的组成部分中包含突变，这表明淀粉和B-葡聚糖代谢和积累之间存在调节联系。在这个项目中，我们想要准确地研究纤维素合成酶超家族的单个成员，特别是CslF和CslH基因家族成员是如何被调控的，特别是那些在谷物发育过程中被打开的基因。这些结果将在大麦育种项目中有重要的应用，在大麦育种项目中，低B-葡聚糖对饲料、麦芽和蒸馏行业非常重要，相反，高B-葡聚糖对人类健康是可取的。因此，能够利用我们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，作为一种降胆固醇的‘健康超级食品’，作为替代性增稠剂或新的食品产品开发，如小麦面粉的添加剂/替代物)。

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).