Characterization of the glycinin gene family in soybean.

Abstract

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.

Soybean Glycinin G1 Acidic Chain Shares IgE Epitopes with Peanut Allergen Ara h 3

“…Further analysis of soybean glycinin structure in comparison with similar legume proteins reveals that the epitopes reported here may be located in a particularly allergenic region of legume seed storage proteins. The primary structure of glycinin, in comparison with similar legume family proteins, possesses three variable regions [24]. These regions have been identified as residing at the surface of the glycinin subunit since proteolytic cleavage occurs at or near these variable regions [24, 29].…”

“…The primary structure of glycinin, in comparison with similar legume family proteins, possesses three variable regions [24]. These regions have been identified as residing at the surface of the glycinin subunit since proteolytic cleavage occurs at or near these variable regions [24, 29]. Both epitope A and epitope B reside in a domain between two variable regions (variable region 2, residues Q188–E216, and the hypervariable region, residues T269–K306 [24]) that may represent a particularly allergenic domain of legume seed storage proteins.…”

“…Soybean glycinin exhibits high sequence identity to the 11S proteins pea legumin A (64%) [24], rice glutelin (37%) [24], and peanut glycinin (62%) [1]. Lower identity scores are obtained for soybean glycinin with the 7S proteins French bean phaseolin, soybean α-subunit of β-conglycinin, and peanut vicilin (17–20%).…”

“…The acidic and basic chains are translated as a continuous polypeptide before being posttranslationally cleaved to form the ∼40-kD acidic and ∼20-kD basic chains that are linked through internal disulfides [24, 25]. Soybean glycinin is a gene family with the nonrandom assembly of acidic and basic chains into the subunits A 1a B 2 (G1), A 2 B 1a (G2), A 1b B 1b (G3), A 5 A 4 B 3 (G4), and A 3 B 4 (G5) [23, 24]. The binding of IgE from soy-allergic individuals has been found to soybean glycinin acidic chains [26], whereas the basic chains did not bind IgE [26, 27].…”

Separation of Cultivars of Soybeans by Chemometric Methods Using Near Infrared Spectroscopy

“…Studies have already concluded that seed composition can be strongly affected by genetic and environmental factors and that the genetic background of each variety controls seed composition and how much of the multi-subunit storage proteins contribute for total seed protein of soybeans (Krishnan, 2001;Nielsen et al, 1989;Zarkadas et al, 2007).…”