In the rice endosperm cells, glutelins are synthesized on rough endoplasmic reticulum as proglutelins and are sorted to the protein storage vacuoles （PSVs） called protein body IIs （PBIIs）, where they are converted...In the rice endosperm cells, glutelins are synthesized on rough endoplasmic reticulum as proglutelins and are sorted to the protein storage vacuoles （PSVs） called protein body IIs （PBIIs）, where they are converted to the mature forms. Dense vesicle （DV）-mediated trafficking of proglutelins in rice seeds has been proposed, but the post-Golgi control of this process is largely unknown. Whether DV can fuse directly with PSV is another matter of debate. In this study, we propose a regulatory mechanism underlying DV-mediated, post-Golgi proglutelin trafficking to PBII （PSV）. gpa2, a loss- of-function mutant of OsVPS9A, which encodes a GEF of OsRAB5A, accumulated uncleaved proglutelins. Proglutelins were mis-targeted to the paramural bodies and to the apoplast along the cell wall in the form of DVs, which led to a con- comitant reduction in PBII size. Previously reported gpal, mutated in OsRab5a, has a similar phenotype, while gpalgpa2 double mutant exacerbated the conditions. In addition, OsVPS9A interacted with OsRAB5A in vitro and in vivo. We con- cluded that OsVPS9A and OsRAB5A may work together and play a regulatory role in DV-mediated post-Golgi proglutelin trafficking to PBII （PSV）. The evidence that DVs might fuse directly to PBII （PSV） to deliver cargos is also presented.展开更多
基金projects from the Ministry of Agriculture of China for Transgenic Research，the Program for New Century Excellent Talents in University of Ministry of Education of China，the Fundamental Research Funds for the Central Universities，the Earmarked Fund for Modern Agro-industry Technology Research System,and the Jiangsu Natural Science Foundation Project，Science and Technology Development Program
文摘In the rice endosperm cells, glutelins are synthesized on rough endoplasmic reticulum as proglutelins and are sorted to the protein storage vacuoles （PSVs） called protein body IIs （PBIIs）, where they are converted to the mature forms. Dense vesicle （DV）-mediated trafficking of proglutelins in rice seeds has been proposed, but the post-Golgi control of this process is largely unknown. Whether DV can fuse directly with PSV is another matter of debate. In this study, we propose a regulatory mechanism underlying DV-mediated, post-Golgi proglutelin trafficking to PBII （PSV）. gpa2, a loss- of-function mutant of OsVPS9A, which encodes a GEF of OsRAB5A, accumulated uncleaved proglutelins. Proglutelins were mis-targeted to the paramural bodies and to the apoplast along the cell wall in the form of DVs, which led to a con- comitant reduction in PBII size. Previously reported gpal, mutated in OsRab5a, has a similar phenotype, while gpalgpa2 double mutant exacerbated the conditions. In addition, OsVPS9A interacted with OsRAB5A in vitro and in vivo. We con- cluded that OsVPS9A and OsRAB5A may work together and play a regulatory role in DV-mediated post-Golgi proglutelin trafficking to PBII （PSV）. The evidence that DVs might fuse directly to PBII （PSV） to deliver cargos is also presented.
