Butow B J, Gale K R, Ikea J, Juhász A, Bedö Z, Tamás L, Gianibelli M C
CSIRO Plant Industry, GPO Box 1600, Canberra, ACT, 2601, Australia.
Theor Appl Genet. 2004 Nov;109(7):1525-35. doi: 10.1007/s00122-004-1776-8. Epub 2004 Aug 31.
Increased expression of the high molecular weight glutenin subunit (HMW-GS) Bx7 is associated with improved dough strength of wheat (Triticum aestivum L.) flour. Several cultivars and landraces of widely different genetic backgrounds from around the world have now been found to contain this so-called 'over-expressing' allelic form of the Bx7 subunit encoded by Glu-B1al. Using three methods of identification, SDS-PAGE, RP-HPLC and PCR marker analysis, as well as pedigree information, we have traced the distribution and source of this allele from a Uruguayan landrace, Americano 44D, in the mid-nineteenth century. Results are supported by knowledge of the movement of wheat lines with migrants. All cultivars possessing the Glu-B1al allele can be identified by the following attributes: (1) the elution of the By sub-unit peak before the Dx sub-unit peak by RP-HPLC, (2) high expression levels of Bx7 (>39% Mol% Bx), (3) a 43 bp insertion in the matrix-attachment region (MAR) upstream of the gene promoter relative to Bx7 and an 18 bp nucleotide duplication in the coding region of the gene. Evidence is presented indicating that these 18 and 43 bp sequence insertions are not causal for the high expression levels of Bx7 as they were also found to be present in a small number of hexaploid species, including Chinese Spring, and species expressing Glu-B1ak and Glu-B1a alleles. In addition, these sequence inserts were found in different isolates of the tetraploid wheat, T. turgidum, indicating that these insertion/deletion events occurred prior to hexaploidization.
高分子量麦谷蛋白亚基（HMW - GS）Bx7表达量的增加与小麦（普通小麦）面粉面团强度的提高有关。现已发现，来自世界各地、遗传背景差异很大的几个品种和地方品种都含有这种由Glu - B1al编码的Bx7亚基的所谓“过表达”等位基因形式。通过三种鉴定方法，即SDS - PAGE、RP - HPLC和PCR标记分析，以及系谱信息，我们追溯了这个等位基因在19世纪中叶来自乌拉圭地方品种Americano 44D的分布和来源。小麦品系随移民的流动情况的相关知识也支持了这一结果。所有拥有Glu - B1al等位基因的品种都可以通过以下特征来鉴定：（1）RP - HPLC分析中By亚基峰在Dx亚基峰之前洗脱；（2）Bx7的高表达水平（>39% Mol% Bx）；（3）相对于Bx7，基因启动子上游的基质附着区域（MAR）中有一个43 bp的插入，以及基因编码区中有一个18 bp的核苷酸重复。有证据表明，这18和43 bp的序列插入并非导致Bx7高表达水平的原因，因为在包括中国春在内的少数六倍体物种以及表达Glu - B1ak和Glu - B1a等位基因的物种中也发现了它们。此外，在四倍体小麦硬粒小麦的不同分离株中也发现了这些序列插入，这表明这些插入/缺失事件发生在六倍体化之前。
