title: Formation mechanism of the internal structure of type I protein bodies in rice endosperm: relationship between the localization of prolamin species and the expression of individual genes.
abstract: Rice prolamins, a group of seed storage proteins, are synthesized on the rough endoplasmic reticulum (ER) and form type I protein bodies (PB-Is) in endosperm cells. Rice prolamins are encoded by a multigene family. In this study, the spatial accumulation patterns of various prolamin species in rice endosperm cells were investigated to determine the mechanism of formation of the internal structure of PB-Is. Immunofluorescence microscopic analysis of mature endosperm cells showed that the 10 kDa prolamin is mainly localized in the core of the PB-Is, the 13b prolamin is localized in the inner layer surrounding the core and the outermost layer, and the 13a and 16 kDa prolamins are localized in the middle layer. Real-time RT-PCR analysis showed that expression of the mRNA for 10 kDa prolamin precedes expression of 13a, 13b-1 and 16 kDa prolamin in the developing stages. mRNA expression for 13b-2 prolamin occurred after that of the other prolamin species. Immunoelectron microscopy of developing seeds showed that the 10 kDa prolamin polypeptide initially accumulates in the ER, and then 13b, 13a, 16 kDa and 13b prolamins are stacked in layers within the ER. Studies with transgenic rice seeds expressing prolamin-GFP fusion proteins under the control of native and constitutive promoters indicated that the temporal expression pattern of prolamin genes influenced the localization of prolamin proteins within the PB-Is. These findings indicate that the control of gene expression of prolamin species contributes to the internal structure of PB-Is.
authors.affiliation: Laboratory of Genetic Engineering, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Shimogamo, Kyoto 606-8522, Japan.
authors.forename: Yuhi
authors.initials: Y
authors.lastname: Saito
authors.forename: Takanari
authors.initials: T
authors.lastname: Shigemitsu
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Yamasaki
authors.forename: Ai
authors.initials: A
authors.lastname: Sasou
authors.forename: Futami
authors.initials: F
authors.lastname: Goto
authors.forename: Koichi
authors.initials: K
authors.lastname: Kishida
authors.forename: Masaharu
authors.initials: M
authors.lastname: Kuroda
authors.forename: Kunisuke
authors.initials: K
authors.lastname: Tanaka
authors.forename: Shigeto
authors.initials: S
authors.lastname: Morita
authors.forename: Shigeru
authors.initials: S
authors.lastname: Satoh
authors.forename: Takehiro
authors.initials: T
authors.lastname: Masumura
mesh_terms: D056625:Endosperm / Q000254:growth & development* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005810:Multigene Family; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D055315:Prolamins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000166:cytology* / Q000378:metabolism
chemical_list: D055315:Prolamins