We characterized the structure, organization, and expression of genes that encode the soybean glycinins, a family of storage proteins synthesized exclusively in seeds during embryogenesis. Five genes encode the predominant glycinin subunits found in soybeans, and they have each been cloned, sequenced, and compared. The five genes have diverged into two subfamilies that are designated as Group-I and Group-II glycinin genes. Each glycinin gene contains four exons and three introns like genes that encode related proteins in other legumes. Two other genes have been identified and designated as "glycinin-related" because they hybridize weakly with the five glycinin genes. Although not yet characterized, glycinin-related genes could encode other glycinin subunit families whose members accumulate in minor amounts in seeds. The three Group-I glycinin genes are organized into two chromosomal domains, each about 45 kilobase pairs in length. The two domains have a high degree of homology, and contain at least five genes each that are expressed either in embryos or in mature plant leaves. Gel blot studies with embryo mRNA, as well as transcription studies with 32P-RNA synthesized in vitro from purified embryo nuclei, indicate that glycinin and glycinin-related genes become transcriptionally activated in a coordinated fashion early in embryogenesis, and are repressed coordinately late in seed development. In addition to transcriptional control processes, posttranscriptional events also are involved in regulating glycinin and glycinin-related mRNA levels during embryogenesis.

We characterized the structure, organization, and expression of genes that encode the soybean glycinins, a family of storage proteins synthesized exclusively in seeds during embryogenesis. Five genes encode the predominant glycinin subunits found in soybeans, and they have each been cloned, sequenced, and compared. The five genes have diverged into two subfamilies that are designated as Group-I and Group-II glycinin genes. Each glycinin gene contains four exons and three introns like genes that encode related proteins in other legumes. Two other genes have been identified and designated as "glycinin-related" because they hybridize weakly with the five glycinin genes.Although not yet characterized, glycinin-related genes could encode other glycinin subunit families whose members accumulate in minor amounts in seeds. The three Group-I glycinin genes are organized into two chromosomal domains, each about 45 kilobase pairs in length. The two domains have a high degree of homoeology, and contain at least five genes each that are expressed either in embryos or in mature plant leaves. Gel blot studies with embryo mRNA, as well as transcription studies with 3=P-RNA synthesized in vitro from purified embryo nuclei, indicate that gtycinin and glycinin-related genes become transcriptionally activated in a coordinated fashion early in embryogenesis, and are repressed coordinately late in seed development. In addition to transcriptional control processes, posttranscriptional events also are involved in regulating glycinin and glycinin-related mRNA levels during embryogenesis.

We have studied the encapsidation requirements of Turnip yellow mosaic virus (TYMV) genomic and subgenomic RNA using an "agroinfiltration" procedure involving transient expression of RNAs and coat protein (CP) in Nicotiana benthamiana leaves. Although N. benthamiana is a nonhost, expression of TYMV RNA in its leaves by agroinfiltration resulted in efficient local infection and production of the expected virions containing genomic and subgenomic RNAs together with empty capsids. A nonreplicating genomic RNA with a mutation in the polymerase domain was efficiently encapsidated by CP provided in trans, even though RNA levels were a thousand-fold lower than in normal infections. In contrast, encapsidation of CP mRNA was not observed under these conditions, even when the CP mRNA had authentic 5'- and 3'-termini. Deletion of the 3'-tRNA-like structure from the genomic RNA did not alter the encapsidation behavior, suggesting that this feature does not play a role in the encapsidation of TYMV RNA. Our results indicate differences in the encapsidation process between genomic and subgenomic RNAs, and suggest an interaction between RNA replication and the packaging of subgenomic RNA.

Five genes (Gyl through Gys) encode most of the subunits that are assembled into glycinin, a predominant seed storage protein found in soybeans. Restriction fragment length polymorphisms are described that identify four of these five genes (Gyl/Gy~ Gy~ and Gys). The fifth gene (Gy4) is characterized by two alleles, one of which (gY4) causes absence of the subunit. Genetic segregation studies indicate that the five genes are located at four genetic loci within the genome. Gy, and Gy2 are in a direct tandem repeat at one locus, whereas there is a single glycinin gene at each of the other three loci. All four loci segregate independently from one another, and they also segregate independently from the genetic markers for tawny/grey pubescence (T/t), purple/white flower color (W~/w~), light/ dark hilum pigmentation (1~it), black/brown seed coat (R/r), and brown/tan pod color (I~I~L2L2/I~III212). The latter genetic markers are located on linkage groups 1 (t), 8 (w ~), 7 (i), and 2 (r) in the soybean genome, respectively.

Turnip yellow mosaic virus (TYMV) is a positive strand RNA virus that infects mainly Cruciferae plants. In this study, the TYMV genome was modified by inserting an extra subgenomic RNA promoter and a multiple cloning site. This modified TYMV was introduced into Nicotiana benthamiana using a Agrobacterium-mediated T-DNA transfer system (agroinfiltration). When a gene encoding β-glucuronidase or green fluorescent protein was expressed using this modified TYMV as a vector, replication of the recombinant viruses, especially the virus containing β-glucuronidase gene, was severely inhibited.