Abstract
Rice storage proteins compose of prolamin and glutelin, accumulating in PB-I derived from the endoplasmic reticulum (ER) and PB-II derived from vacuole, respectively. To clarify the function of the gene related to the pathway of glutelin biosynthesis, esp2 and glup3 mutants accumulating high amount of proglutelin were analyzed. In esp2 mutant, ER-derived PBs contained proglutelin and prolamin. The endosperm of esp2 mutant lacked protein disulfide isomerase (PDI). In glup3 mutant, proglutelin accumulated into the PB-II with mature glutelin. Glup3 candidate gene showed high homology with the vacuolar processing enzyme (VPE). The candidate gene in glup3 mutant showed the single nucleotide substitution causing the amino acid substitution comparing to the wild type. The VPE activity in glup3 mutant reduced remarkably. These results suggest that PDI and VPE play a role in the sorting of proglutelin and prolamin within the ER and in the cleavage of proglutelin in vacuole, respectively.
