Transgenic rice plants harboring the grain hardness-locus region of Aegilops tauschii

Grain hardness of wheat is determined by the hardness (Ha)-locus region, which contains three friabilin-related genes: puroindoline-a (Pina), puroindoline-b (Pinb) and GSP-1. In our previous study, we produced the transgenic rice plants harboring the large genomic fragment of the Ha-locus region of Aegilops tauschii containing Pina and GSP-1 genes by Agrobacterium-mediated transformation. To examine the effects of the transgenes in the rice endosperms, we firstly confirmed the homozygosity of the T-DNAs in four independent T₂ lines by using fluorescence in situ hybridization (FISH) and DNA gel blot analyses. The transgenes, Pina and GSP-1, were stably expressed in endosperms of the T₃ and T₄ seeds at RNA and protein levels, indicating that the promoters and other regulatory elements on the wheat Ha-locus region function in rice, and that multigene transformation using a large genomic fragment is a useful strategy. The functional contribution of the transgene-derived friabilins to the rice endosperm structure was considered as an increase of spaces between compound starch granules, resulting in a high proportion of white turbidity seeds.