影响大麦制麦品质关键基因的发现
生产啤酒的主要原料是麦芽，而“原麦芽汁浓度”是影响啤酒品质的关键指标，麦芽汁浓度越高，营养价值就越好，同时泡沫细腻持久，酒味醇厚柔和，保管期也长。
大麦制备优质麦芽的工艺对于啤酒酿造行业来说至关重要。随着大麦功能基因组研究的不断深入，利用遗传手段改良大麦的制麦品质性状成为了改善制麦工艺的有效途径。最近，科学家在大麦中发现了一个影响制麦品质性状的关键基因。
大麦中250个谷物QTL位点中有19个与制麦品质性状相关。其中，在4H染色体端粒位置处，有2个QTL位点影响着β-葡聚糖和麦芽提取物产量等制麦品质性状。研究人员利用表达线性分析的方法鉴定出其中一个QTL的主效基因为TLP8（thaumatin-like protein 8）。该基因编码类甜蛋白8，通过氧化还原反应作用于β-葡聚糖，进而影响大麦的制麦品质。该基因的发现不仅有助于人们深入理解制麦工艺的生化反应，而且可以用来改善大麦的制麦品质，造福啤酒酿造行业。
PNAS, June 20 2017
Redox-dependent interaction between thaumatin-like protein and β-glucan influences malting quality of barley
Author
Surinder Singh, Rajiv K. Tripathi, Peggy G. Lemaux, Bob B. Buchanan, and Jaswinder Singh
Plant Science Department, McGill University, Montreal, QC H9X 3V9, Canada
Abstract
Barley is the cornerstone of the malting and brewing industry. It is known that 250 quantitative trait loci (QTLs) of the grain are associated with 19 malting-quality phenotypes. However, only a few of the contributing genetic components have been identified. One of these, on chromosome 4H, contains a major malting QTL, QTL2, located near the telomeric region that accounts, respectively, for 28.9% and 37.6% of the variation in the β-glucan and extract fractions of malt. In the current study, we dissected the QTL2 region using an expression- and microsynteny-based approach. From a set of 22 expressed sequence tags expressed in seeds at the malting stage, we identified a candidate gene, TLP8 (thaumatin-like protein 8), which was differentially expressed and influenced malting quality. Transcript abundance and protein profiles of TLP8 were studied in different malt and feed varieties using quantitative PCR, immunoblotting, and enzyme-linked immunosorbent assay (ELISA). The experiments demonstrated that TLP8 binds to insoluble (1, 3, 1, 4)-β-D glucan in grain extracts, thereby facilitating the removal of this undesirable polysaccharide during malting. Further, the binding of TLP8 to β-glucan was dependent on redox. These findings represent a stride forward in our understanding of the malting process and provide a foundation for future improvements in the final beer-making process.
