Expression of Soybean Seed Storage Protein Genes in Transgenic Plants; their Effects on Expression of a Neighboring Gene and Position Dependency

The β-conglycinin genes, which encode the 7S seed storage proteins of soybean, were previously shown to be relatively independent of “position effects” in transgenic plants, i.e., expression levels of the α′ and β subunit genes of β-conglycinin were relatively consistent on a per gene basis compared with other plant genes. We tested whether the promoter region of the α′ subunit gene confers position independency by introducing a fusion gene comprised of the α′ subunit promoter and the uidA (encoding β-glucuronidase) coding sequence and found that the resultant gene lost its position independency. We also tested the possibility that the β-conglycinin genes have the ability to neutralize “position effects” by placing a position dependent gene adjacent to the β-conglycinin genes. Genes comprised of the promoter that produces the 35S transcript of the cauliflower mosaic virus (CaMV 35S) and the uidA coding region was employed as a position dependent reporter gene. Neither the α′ nor the β subunit genes effectively altered position dependency of the CaMV 35S promoter. We conclude that the coding sequence of the α′ subunit gene is important for its position independency and that the β-conglycinin genes do not affect position dependency of the adjacent genes. Nevertheless the α′ subunit gene acts as an enhancer on the CaMV 35S promoter when the promoters are adjacent to each other.