367 Effects of genetically engineered changes in HMW-GS composition on the mixing properties of wheat flour.

A. E. BLECHL (1), J. W. Lin (1), M. A. Gitt (1), F. Bekes (2), P. W. Gras (2), and O. D. Anderson (1). (1) Agricultural Research Service, USDA, Western Regional Research Center, 800 Buchanan St., Albany, CA 94710, USA; (2) CSIRO Division of Plant Industry, Grain Quality Research Lab, P.O. Box 7, North Ryde, NSW 2113, Australia.

Differences in the allelic composition of high-molecular-weight glutenin subunits (HMW-GS) have often been correlated with differences in the mixing properties and baking performances of wheat flours. In order to verify these correlations and to identify the structural features of these proteins that are essential to their functionality, we have modified their genes in vitro and expressed the new variants in bacteria and transgenic wheat. Modified HMW-GS made in bacteria were tested by adding 10 mg of the purified proteins to 2 g of flour and measuring mixograph parameters after partial reduction and oxidation. The effects of expression of the modified glutenins in transgenic wheat were measured using the 2-g mixograph on flours from their seeds. These results were compared to those from transgenic wheats over-expressing native subunits. These experiments will allow us to assess the effects of 1) native HMW-GS amounts and 2) individual HMW-glutenin protein domains on the mixing properties of wheat flour.