Analysis of Gli-D2 locus identifies a genetic target for simultaneously improving the breadmaking and health related traits of common wheat

Authors: LI, DA - Chinese Academy Of Sciences; JIN, HUAIBIN - Chinese Academy Of Sciences; ZHANG, KUNPU - Chinese Academy Of Sciences; WANG, ZHAOJUN - Chinese Academy Of Sciences; WANG, FAMING - Chinese Academy Of Sciences; ZHAO, YUE - Chinese Academy Of Sciences; HUO, NAXIN - University Of California, Davis; LIU, XIN - Chinese Academy Of Sciences; Gu, Yong; WANG, DAOWEN - Chinese Academy Of Sciences; DONG, LINGLI - Chinese Academy Of Sciences

Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2018
Publication Date: 5/11/2018
Citation: Li, D., Jin, H., Zhang, K., Wang, Z., Wang, F., Zhao, Y., Huo, N., Liu, X., Gu, Y.Q., Wang, D., Dong, L. 2018. Analysis of Gli-D2 locus identifies a genetic target for simultaneously improving the breadmaking and health related traits of common wheat. Plant Journal. 95(3):414-426. https://doi.org/10.1111/tpj.13956.
DOI: https://doi.org/10.1111/tpj.13956

Interpretive Summary: Gliadins (alpha,gamma, omega,delta) and glutenins (HMW-GS and LMW-GS) are two major groups of seed storage proteins in bread wheat. Among them, alpha-gliadins are abundant and contain the major triggers of food allergies and intolerances such as celiac disease. To better understand the properties of alpha-gliadins in wheat end-use and health related traits, we obtained high-quality DNA sequences of the chromosome regions that span the D genome alpha-gliadin gene region (Gli-D2) in a commercial wheat variety, Xiaoyan 81. Sequence analysis identified a total of 10 alpha-gliadin genes. A mutant line lacking the alpha-gliadin gene region (Gli-D2) was generated and used to analyze the effects of alpha-gliadins on breadmaking and agronomic traits. Our study shows that the mutant line exhibited better breadmaking quality than its parent, as well as an increase in the content of the essential amino acid, lysine, in its grain, without penalties in growth performance. This study not only provides insights into the roles of the alpha-gliadins in flour functionality but also facilitates the development of novel strategies for breeding elite wheat varieties with improved end-use and nutritional quality, and reduced potential allergenicity.

Technical Abstract: Gliadins are a major component of wheat seed proteins. However, the complex homoeologous Gli-2 loci (Gli-A2, -B2 and -D2) encoding alpha-gliadins are still poorly understood. Here we analyzed the Gli-D2 locus of Xiaoyan 81 (Xy81), a commercial winter wheat cultivar. A total of 421 kb of Gli-D2 sequence was assembled from sequencing multiple genomic bacterial artificial clones, and 10 alpha-gliadin genes were annotated. Comparative genomic analysis showed that Xy81 carried only eight of the alpha-gliadin genes of the D genome donor Ae. tauschii, two of which had experienced a tandem duplication. A mutant line lacking Gli-D2 (DLGliD2) consistently exhibited better breadmaking quality and dough functionalities than its progenitor Xy81, but without penalties in other agronomic traits. It also had elevated lysine content in the grains. Transcriptome analysis verified the lack of Gli-D2 alpha-gliadin gene expression in DLGliD2. Furthermore, the transcript and protein levels of protein disulfide isomerase were both up-regulated in DLGliD2 grains. Consistent with this finding, DLGliD2 had increased disulfide content in the flour. Our work sheds light on the structure and function of Gli-D2 in commercial wheat, and suggests that the removal of Gli-D2 and the gliadins specified by it is likely useful for simultaneously enhancing the end-use and health related traits of common wheat. Because gliadins and homologous proteins are widely present in grass species, the strategy and information reported here may be broadly useful for improving the quality traits of diverse cereal crops.