Submitted to: Theoretical and Applied Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/22/2006
Publication Date: 11/1/2006
Citation: Martin, J.M., Meyer, F.D., Smidansky, E.D., Wanjugi, H., Blechl, A.E., Giroux, M.J. 2006. Complementation of the pina (null) allele with the wild type pina sequence restores a soft phenotype in transgenic wheat. Theoretical and Applied Genetics. 113(8):1563-1570. Interpretive Summary: Grain hardness is one of the most important characteristics for determining the milling properties and end-uses of wheat seeds. Flours from hard wheats are generally made into breads and buns, while those from soft wheats are made into cookies and cakes. In order to identify the genes and proteins important in grain texture, we transformed a hard wheat with the gene sequence encoding the puroindoline A (PINA) protein. The introduction of this sequence made the grain of the transgenic wheats soft in texture. Molecular analyses confirmed that the introduced genes were expressed at the RNA and protein levels. Three different transgenic lines were grown in field trials and their seeds were harvested and milled into flour. The transgenic wheats yielded more break flour than their parent, which lacked the functional PINA gene and protein. Loaves of bread made from the transgenic wheat flours were similar in size to those made from their parent. This research confirms that a functional puroindoline A gene and protein are essential to make wheat grain soft in texture.
Technical Abstract: The tightly linked puroindoline genes, Pina and Pinb, control grain texture in wheat, with wild type forms of both giving soft, and a sequence alteration in either giving hard wheat. Our goal here was to develop and characterize wheat lines expressing the wild type Pina-D1a sequence in a hard wheat with the null mutation (Pina-D1b) for Pina. A second goal was to determine if the transgenic expression of Pina altered bread quality relative to that of the untransformed Pina null control genotype. Three transgenic lines plus Bobwhite were evaluated in two environments. Milling and bread quality characteristics were determined for the transgenic lines and Bobwhite. The three transgenic lines had soft phenotype. The soft phenotype was accompanied by increases in Pina transcript accumulation. Total TX114 extractable PINA and PINB increased to 2.5 to 5.5 times those from a soft wheat control, and friabilin, PINA and PINB bound to starch, increased 3.8 to 7.8 times those of the soft wheat control. Bobwhite showed no starch bound PINA, but transgenic lines had levels from 5.3 to 13.7 times those of the soft wheat control. Starch bound PINB also increased relative to the Bobwhite (hard) parent 3.7 to 10 times. The three transgenic lines had higher break flour yield but lower flour yield than Bobwhite. Loaf volume for one of the transgenic lines was equal to that of the Bobwhite control. The transgenic expression of wild type Pina sequence in the Pina null genotype gave soft grain with the characteristics of soft wheats including increased starch bound friabilin and higher break flour yield.