To better understand the transcriptional regulation of high molecular weight glutenin subunit (HMW-GS) expression, we isolated four Glu-1Bx promoters from six wheat cultivars exhibiting diverse protein expression levels. The activities of the diverse Glu-1Bx promoters were tested and compared with β-glucuronidase (GUS) reporter fusions. Although all the full-length Glu-1Bx promoters showed endosperm-specific activities, the strongest GUS activity was observed with the 1Bx7<sup>OE</sup> promoter in both transient expression assays and stable transgenic rice lines. A 43 bp insertion in the 1Bx7<sup>OE</sup> promoter, which is absent in the 1Bx7 promoter, led to enhanced expression. Analysis of promoter deletion constructs confirmed that a 185 bp MITE (miniature inverted-repeat transposable element) in the 1Bx14 promoter had a weak positive effect on Glu-1Bx expression, and a 54 bp deletion in the 1Bx13 promoter reduced endosperm-specific activity. To investigate the effect of the 43 bp insertion in the 1Bx7<sup>OE</sup> promoter, a functional marker was developed to screen 505 Chinese varieties and 160 European varieties, and only 1Bx7-type varieties harboring the 43 bp insertion in their promoters showed similar overexpression patterns. Hence, the 1Bx7<sup>OE</sup> promoter should be important tool in crop genetic engineering as well as in molecular assisted breeding. © 2014 Geng et al.
Geng, Y., Pang, B., Hao, C., Tang, S., Zhang, X., & Li, T. (2014). Expression of wheat high molecular weight glutenin subunit 1Bx is affected by large insertions and deletions located in the upstream flanking sequences. PLoS ONE, 9(8). https://doi.org/10.1371/journal.pone.0105363