Journal of Cereal Science 30 (1999) 115–120 Article No. jcrs.1998.0265, available online at http://www.idealibrary.com on Overexpression of a Gluten Protein in Transgenic Wheat Results in Greatly Increased Dough Strength L. Rooke*, F. Be ´ke ´s†, R. Fido‡, F. Barro*, P. Gras†, A. S. Tatham‡, P. Barcelo¶, P. Lazzeri¶ and P. R. Shewry‡ * IACR-Rothamsted, Harpenden, Herts AL5 2LQ, U.K.; † Plant Science CRC, CSIRO, North Ryde, NSW 2113, Australia; ‡ IACR-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS41 9AF, U.K.; ¶ DuPont U.K., IACR-Rothamsted, Harpenden, Herts AL5 2LQ, U.K. Received 6 November 1998 ABSTRACT The transgenic wheat line B73-6-1 contains additional genes encoding a gluten protein called HMW subunit 1Dx5, resulting in a four-fold increase in the proportion of this component in the seed proteins and corresponding increases in the proportions of total HMW subunits and total glutenins. This is associated with a dramatic increase in dough strength, as measured using a small scale Mixograph, with dough produced from B73-6-1 being too strong to be used in conventional breadmaking.  1999 Academic Press Keywords: breadmaking quality, gluten, glutenin, HMW subunits, transformation, wheat. about 2% of the total grain protein 4,5 , the variation INTRODUCTION in HMW subunit gene expression may result in a The high molecular weight (HMW) subunits of quantitative effect on the total amount of HMW wheat glutenin have been studied in detail because subunit protein and hence on quality. In addition, of their role in determining the processing prop- allelic variation in the composition and properties erties of the grain 1–3 . In particular, they are con- of the expressed subunits may have qualitative sidered to be major determinants of the viscoelastic effects on processing properties, with allelic sub- properties that enable wheat dough to be processed units being associated with either good or poor into bread, pasta and various other foods. Cultivars quality 1,6 . The relationship between HMW subunit of hexaploid bread wheat contain six HMW sub- gene expression and quality has made this group unit genes, with two closely linked genes on each of proteins an attractive target for manipulation of the homoeologous group one chromosomes 1 . in transgenic wheat, with the transfer and ex- However, some of these genes may be silent, pression of additional HMW subunits reported by resulting in variation in the number of expressed three separate groups 7–9 . In one case the expression HMW subunit proteins from three to six. Since was associated with improved functional properties each HMW subunit accounts, on average, for but the line used as recipient L88-31 10 , was selected as having a low intrinsic level of quality relating to the presence of only two HMW subunits (called 1B x17+1By18) 8 . ‡ Fax number for correspondence: +44 (0) 1275 394299 0733–5210/99/090115+06 $30.00/0  1999 Academic Press