The success of hexaploid bread wheat(Triticum aestivum L.,2n=6x=42,AABBDD) as a global food crop is attributed to its allopolyploidization,a process with a hybridization between the cultivated tetraploid Triticum turgidum(2n=4x=28,AABB) and the wild goatgrass Aegilops tauschii(2n=2x=14,DD) and an event of chromosome doubling.In this talk,we will show the recent results from our studies of the two stages –hybridization and chromosome doubling – on homoeologous gene expressions.We will also demonstrate the contribution of such regulation to hexaploid wheat growth vigor and adaption and possible underlining small RNA mediated molecular mechanisms.