Freeman Jackie, Lovegrove Alison, Wilkinson Mark David, Saulnier Luc, Shewry Peter Robert, Mitchell Rowan Andrew Craig
Plant Biology and Crop Science, Rothamsted Research, Harpenden, UK.
INRA Centre de Recherche Angers-Nantes, Nantes, France.
Plant Biotechnol J. 2016 Jan;14(1):109-16. doi: 10.1111/pbi.12361. Epub 2015 Mar 27.
Arabinoxylan (AX) is the dominant component within wheat (Triticum aestivum L.) endosperm cell walls, accounting for 70% of the polysaccharide. The viscosity of aqueous extracts from wheat grain is a key trait influencing the processing for various end uses, and this is largely determined by the properties of endosperm AX. We have previously shown dramatic effects on endosperm AX in transgenic wheat by down-regulating either TaGT43_2 or TaGT47_2 genes (orthologues to IRX9 and IRX10 in Arabidopsis, respectively) implicated in AX chain extension and the TaXAT1 gene responsible for monosubstitution by 3-linked arabinose. Here, we use these transgenic lines to investigate the relationship between amounts of AX in soluble and insoluble fractions, the chain-length distribution of these measured by intrinsic viscosity and the overall effect on extract viscosity. In transgenic lines expressing either the TaGT43_2 or TaGT47_2 RNAi transgenes, the intrinsic viscosities of water-extractable (WE-AX) and of a water-insoluble alkaline-extracted fraction (AE-AX) were decreased by between 10% and 50% compared to control lines. In TaXAT1 RNAi lines, there was a 15% decrease in intrinsic viscosity of WE-AX but no consistent effect on that of AE-AX. All transgenic lines showed decreases in extract viscosity with larger effects in TaGT43_2 and TaGT47_2 RNAi lines (by up to sixfold) than in TaXAT1 RNAi lines (by twofold). These effects were explained by the decreases in amount and chain length of WE-AX, with decreases in amount having the greater influence. Extract viscosity from wheat grain can therefore be greatly decreased by suppression of single gene targets.
阿拉伯木聚糖（AX）是小麦（Triticum aestivum L.）胚乳细胞壁中的主要成分，占多糖的70%。小麦籽粒水提取物的粘度是影响各种最终用途加工的关键特性，这在很大程度上由胚乳AX的特性决定。我们之前已经表明，通过下调与AX链延伸相关的TaGT43_2或TaGT47_2基因（分别与拟南芥中的IRX9和IRX10直系同源）以及负责3-连接阿拉伯糖单取代的TaXAT1基因，对转基因小麦中的胚乳AX有显著影响。在这里，我们使用这些转基因系来研究可溶性和不溶性组分中AX的含量、通过特性粘度测量的这些AX的链长分布以及对提取物粘度的总体影响。在表达TaGT43_2或TaGT47_2 RNAi转基因的转基因系中，与对照系相比，水可提取（WE-AX）和水不溶性碱提取级分（AE-AX）的特性粘度降低了10%至50%。在TaXAT1 RNAi系中，WE-AX的特性粘度降低了15%，但对AE-AX的特性粘度没有一致的影响。所有转基因系的提取物粘度均降低，TaGT43_2和TaGT47_2 RNAi系的影响更大（高达六倍），而TaXAT1 RNAi系的影响较小（两倍）。这些影响可以通过WE-AX的含量和链长的降低来解释，其中含量的降低影响更大。因此，通过抑制单个基因靶点可以大大降低小麦籽粒的提取物粘度。
