title: Accumulation of rice prolamin-GFP fusion proteins induces ER-derived protein bodies in transgenic rice calli.
abstract: KEY MESSAGE                 :                                     We showed that rice prolamin polypeptides formed ER-derived PBs in transgenic rice calli, and that this heterologous transgene expression system is suitable for studying the mechanism of rice PB-I formation.                                                                  Rice prolamins, alcohol-soluble seed storage proteins, accumulate directly within the rough endoplasmic reticulum (ER) lumen, leading to the formation of ER-derived type I protein bodies (PB-Is) in rice seed. Because rice prolamins do not possess a well-known ER retention signal such as K(H)DEL, or a unique sequence for retention in the ER such as a tandem repeat domain of maize and wheat prolamins, the mechanisms of prolamin accumulation in the ER and PB-I formation are poorly understood. In this study, we examined the formation mechanisms of PBs by expressing four types of rice prolamin species fused to green fluorescent protein (GFP) in transgenic rice calli. Each prolamin-GFP fusion protein was stably accumulated in rice calli and formed ER-derived PBs. In contrast, GFP fused with the signal peptide of prolamin was secreted into the intercellular space in rice calli. In addition, each of the four types of prolamin-GFP fusion proteins was co-localized with the ER chaperone binding protein. These results suggest that the mature polypeptide of prolamin is capable of being retained in the ER and induce the formation of PBs in non-seed tissue, and that the rice callus heterologous transgene expression system is useful for studying the mechanisms of rice PB-I formation.
authors.affiliation: Laboratory of Genetic Engineering, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Shimogamo, Kyoto 606-8522, Japan.
authors.forename: Takanari
authors.initials: T
authors.lastname: Shigemitsu
authors.forename: Takehiro
authors.initials: T
authors.lastname: Masumura
authors.forename: Shigeto
authors.initials: S
authors.lastname: Morita
authors.forename: Shigeru
authors.initials: S
authors.lastname: Satoh
mesh_terms: D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D055315:Prolamins / Q000378:metabolism*; D021381:Protein Transport; D011993:Recombinant Fusion Proteins; D012639:Seeds / Q000235:genetics / Q000378:metabolism; D046509:Tissue Culture Techniques
chemical_list: D010940:Plant Proteins; D055315:Prolamins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins