Upstream regulatory sequences from two β-conglycinin genes.

Genes encoding the β-conglycinin seed storage proteins of soybean are expressed only in seeds during specific stages of development. The different subunits of β-conglycinin, α′, α and β, are encoded by distinct members of a gene family. Yet there are marked differences in the regulation of the genes encoding the α′/α and β subunits. Previous work (Chen et al., EMBO J 7: 297–302, 1988) identified a seed specific transcriptional enhancer upstream of a gene encoding the α′ subunit. Mutations were made within this region to discern its functional components. Among those identified is a 62 bp region (between −77 and −140) that contains a vicilin box consensus sequence as well as a sequence that binds the soybean nuclear factor SEF4 in vitro. A second region, which contains a sequence homologous to the core of the legumin box consensus (i.e., CATGCAT-like or RY repeat element) at −246, was also shown to affect the activity of this enhancer in transgenic plants. A series of 5′ terminal deletions were used to identify regulatory elements upstream of the β subunit gene. Two regions were identified (from −553 to −442 and from −308 to −72) that, when deleted, led to a marked reduction in gene expression. Both of these elements contain sequences that bind SEF4 in vitro. The distal element also contains an AT-rich segment that recognizes a second nuclear factor, SEF1, in vitro. Neither of these elements contains any homology to the vicilin box consensus.