Are Regulated by Transcriptional and Posttranscriptional Processes

We investigated the chromosomal organization and developmental regulation of soybean 8-conglycinin genes. The 8-conglycinin gene family contains at least 15 members divided into two major groups encoding 2.5-kilobase and 1.7-kilobase embryo mRNAs. 8-Conglycinin genes are clustered in severa1 DNA regions and are highly homologous along their entire lengths. The two groups differ by the presence or absence of specific DNA segments. These DNA segments account for the size differences in 8-conglycinin mRNAs. The 2.5-kilobase and 1.7-kilobase 8-conglycinin mRNAs accumulate and decay at different times during embryogenesis. By contrast, genes encoding these mRNAs are transcriptionally activated and repressed at the same time periods. Our studies indicate that the 8-conglycinin family evolved by both duplication and insertion/deletion events, and that 8-conglycinin gene expression is regulated at both the transcriptional and posttranscriptional levels.