title: Co-expression of soybean glycinins A1aB1b and A3B4 enhances their accumulation levels in transgenic rice seed.
abstract: The soybean major storage protein glycinin is encoded by five genes, which are divided into two subfamilies. Expression of A3B4 glycinin in transgenic rice seed reached about 1.5% of total seed protein, even if expressed under the control of strong endosperm-specific promoters. In contrast, expression of A1aB1b glycinin reached about 4% of total seed protein. Co-expression of the two proteins doubled accumulation levels of both A1aB1b and A3B4 glycinins. This increase can be largely accounted for by their aggregation with rice glutelins, self-assembly and inter-glycinin interactions, resulting in the enrichment of globulin and glutelin fractions and a concomitant reduction of the prolamin fraction. Immunoelectron microscopy indicated that the synthesized A1aB1b glycinin was predominantly deposited in protein body-II (PB-II) storage vacuoles, whereas A3B4 glycinin is targeted to both PB-II and endoplasmic reticulum (ER)-derived protein body-I (PB-I) storage structures. Co-expression with A1aB1b facilitated targeting of A3B4 glycinin into PB-II by sequestration with A1aB1b, resulting in an increase in the accumulation of A3B4 glycinin.
authors.affiliation: Transgenic Crop Research and Development Center, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602 Japan. takaiwa@nias.affrc.go.jp
authors.forename: Fumio
authors.initials: F
authors.lastname: Takaiwa
authors.forename: Chiyoko
authors.initials: C
authors.lastname: Sakuta
authors.forename: Seon-Kang
authors.initials: SK
authors.lastname: Choi
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Tada
authors.forename: Takayasu
authors.initials: T
authors.lastname: Motoyama
authors.forename: Shigeru
authors.initials: S
authors.lastname: Utsumi
mesh_terms: D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005916:Globulins / Q000235:genetics / Q000378:metabolism*; D005983:Glutens / Q000378:metabolism; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D055315:Prolamins; D018749:RNA, Plant / Q000235:genetics; D012639:Seeds / Q000235:genetics / Q000378:metabolism*; D012995:Solubility; D030262:Soybean Proteins / Q000235:genetics / Q000378:metabolism*; D013025:Glycine max / Q000235:genetics*; D014170:Transformation, Genetic
chemical_list: D005916:Globulins; D010940:Plant Proteins; D055315:Prolamins; D018749:RNA, Plant; D030262:Soybean Proteins; C093157:glycinin A(3)B(4); D005983:Glutens; C011474:glycinin