TaAAP6-3B, a regulator of grain protein content selected during wheat improvement

Background: The content of grain protein (GPC) in cereals is an important part of total protein in human food. Exploring and utilizing new GPC genes is one of the most effective approaches for wheat quality breeding. Results: Three homoeologues of TaAAP6(-3A, 3B, 3D) were cloned by homology cloning from OsAAP6. Temporal and spatial expression analysis showed that TaAAP6homoeologues were preferentially expressed in developing grains, and TaAAP6-3B may play a major role in regulating GPC in wheat. Association analysis indicated thatTaAAP6-3B-I is significantly correlated with higher GPC than that of TaAAP6-3B-II for 115 wheat lines in all five environments. TaAAP6-3B-I, the favored allele of TaAAP6-3B, was preferentially expressed in preliminary developing grain stage. Two functional markers were developed to discriminate 197F(2)populations and the result showed that TaAAP6-3B-I (high-protein content) was completely dominant. Two cis-regulatory elements appear to be associated with high GPC were found in the 5'UTR of TaAAP6-3B-I. The change of the TaAAP6-3B locus types indicated that the gene was subjected to selection pressures during long process of artificial selection. Conclusions: TaAAP6-3B is a regulator of GPC and its favored allele TaAAP6-3BI exhibits an obvious potential application in wheat high-GPC breeding.