Abstract
Small GTPase Rab5a participates in vesicular transport. Rice glutelin is synthesized on endoplasmic reticulum (ER) as a precursor, which is transported via Golgi to protein storage vacuole. Mutation for rice Rab5a structural gene, glup4 endosperm accumulates glutelin precursor. But the function of Rab5a to intracellular transport of glutelin is not clear. Immunofluorescence microscopy demonstrated that novel structure including glutelin precursor was observed in glup4 allelic lines, indicating that the formation of the structure was due to mutation of Rab5a gene. Since it was suggested that the structure was derived from ER, glutelin precursor might be accumulated within ER. Confocal microscopy indicated that the structure included β-glucan, a component of cell wall polysaccharides. As β-glucan is synthesized in Golgi, the structure has both properties of ER and Golgi. On a conclusion, Rab5a functions the formation of endomembrane system in rice endosperm and participates in intracellular transport of glutelin precursor.
