|Nguyen, Son - TOURO COLLEGE,VALLEJO,CA|
Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 18, 2006
Publication Date: March 1, 2007
Citation: Blechl, A.E., Lin, J.W., Nguyen, S., Chan, R., Anderson, O.D., Dupont, F.M. 2007. Transgenic wheats with elevated levels of dx5 and/or dy10 high-molecular-weight glutenin subunits yield doughs with increased mixing strength and tolerance. Journal of Cereal Science. 45:172-183 Interpretive Summary: One of the most important characteristics of wheat end-use functionality is dough strength, a property that determines whether a wheat is suitable for making breads, noodles or cookies. One class of seed proteins, the high-molecular-weight glutenins, has a major influence on dough elasticity, but it is not known which structural components of these proteins are important for their role in building the gluten polymer. The research in this paper explores the effects of changing the levels of two of these proteins, Dx5 and Dy10. In nature, these proteins are always found together because they are encoded by two linked genes. By using genetic transformation, we were able to change the levels of each protein independently. Flours prepared from the transgenic wheats were assessed by biochemical and micro-mixing tests. The results show that Dy10 has less effect on polymer formation and dough strengthening than Dx5. The doughs formed by wheat with increases in Dy10 are easier to mix than those with increases in Dx5, but still stronger and more tolerant of mixing than the doughs from the non-transformed parental wheat cultivar. The experiments demonstrate that dough properties of wheat can be improved by genetic transformation, but that both the amounts and types of added proteins are important for dough hydration and mixing.
Technical Abstract: In order to test the effects of independently increasing the in vivo levels of high-molecular-weight glutenin subunits (HMW-GS) Dx5 and Dy10 on wheat flour properties, we increased the copy numbers of their corresponding genes by genetic transformation. Thirteen transformants with increases in one or both subunits were chosen for biochemical and functional characterization by solvent fractionation, RP-HPLC, SDS-sedimentation, and micro-mixing. Increases in Dx5 and Dy10 contents ranged from 1.4- to 3.5-fold and 1.2- to 5.4-fold, respectively, and generally resulted in increased polymeric protein, increased mixing times and tolerances, and lower peak resistances. Increases in Dx5 content had larger effects on most parameters than comparable increases in Dy10. Flours with more than 2.6-times the native levels of Dx5 could not be mixed under standard 2-g mixograph conditions, while flours with 5.4-time the native levels of Dy10 could be mixed if sufficient time was allowed. Increases in Dx5 and Dy10 had additive effects on mixing behavior. These experiments demonstrate that dough mixing strength and tolerance can be increased by raising the levels of native HMW-GS Dx5 or Dy10, but that the effects of the two subunits are quantitatively and qualitatively different.