Abstract
Rab GTPases regulate the intracellular membrane trafficking events and are activated by Guanine nucleotide exchange factor (GEFs). The trafficking of rice glutelin involves membrane traffic pathway, which has been mainly described as that glutelins are initially synthesized on the endoplasmic reticulum as 57-KD precursor, then transported via the Golgi apparatus to protein storage vacuole (PSV), proteolytically cleaved and accumulate in PSV. In our previous study, both of glup4 and glup6 mutants for Rab5a and GEF, respectively, showed the novel structure containing the proglutelin in the endosperm. The immune precipitation analysis of the Glup6-GEF and Glup4-Rab5 proteins revealed that both proteins were interacted each other, suggesting that the Glup6-GEF activates Glup4-Rab5. The microscopy analysis of the endosperm in double recessive type of glup4 and glup6 mutants showed more severe novel structure containing the proglutelins than each single mutant. These results suggest the possibility that the Glup6-GEF activates also the other Rab proteins and the Glup4-Rab5a is activated also by the other GEF proteins.
