Vacuolar sorting receptors （VSRs） are type I integral membrane proteins that mediate the vacuolar transport of soluble cargo proteins via prevacuolar compartments （PVCs） in plants. Confocal immunofluorescent and i...Vacuolar sorting receptors （VSRs） are type I integral membrane proteins that mediate the vacuolar transport of soluble cargo proteins via prevacuolar compartments （PVCs） in plants. Confocal immunofluorescent and immunogold Electron Microscope （EM） studies have localized VSRs to PVCs or multivesicular bodies （MVBs） and trans-Golgi network （TGN） in various plant cell types, including suspension culture cells, root cells, developing and germinating seeds. Here, we provide evidence that VSRs reach plasma membrane （PM） in growing pollen tubes. Both immunofluorescent and immunogold EM studies with specific VSR antibodies show that, in addition to the previously demonstrated PVC/MVB localization, VSRs also localize to PM in lily and tobacco pollen tubes prepared from chemical fixation or high-pressure freezing/frozen substitution. Such a PM localization suggests an additional role of VSR proteins in mediating protein transport to PM and endocytosis in growing pollen tubes. Using a high-speed Spinning Disc Confocal Microscope, the possible fusion between VSR-positive PVC organelles and the PM was also observed in living tobacco pollen tubes transiently expressing the PVC reporter GFP-VSR. In contrast, the lack of a prominent PM localization of GFP-VSR in living pollen tubes may be due to the highly dynamic situation of vesicular transport in this fast-growing cell type.展开更多
Plant prevacuolar compartments （PVCs）, or multivesicular bodies （MVBs）, are single membrane-bound organelles that play important roles in mediating protein trafficking to vacuoles in the secretory pathway. PVC/MVB...Plant prevacuolar compartments （PVCs）, or multivesicular bodies （MVBs）, are single membrane-bound organelles that play important roles in mediating protein trafficking to vacuoles in the secretory pathway. PVC/MVB also serves as a late endosome in the endocytic pathway in plants. Since the plant PVC was iden- tified as an MVB more than 10 years ago,-great progress has been made toward the understanding of PVC/ MVB function and biogenesis in plants. In this review, we first summarize previous research into the iden- tification and characterization of plant PVCs/MVBs, and then highlight recent advances on the mechanisms underlying intraluminal vesicle formation and maturation of plant PVCs/MVBs. In addition, we discuss the possible crosstalk that appears to occur between PVCs/MVBs and autophagosomes during autophagy in plants. Finally, we list some open questions and present future perspectives in this field.展开更多
Transport of vacuolar proteins from Golgi apparatus or trans-Golgi network （TGN） to vacuoles is a receptor-mediated process via an intermediate membrane-bound prevacuolar compartment （PVC） in plant cells. Both vac...Transport of vacuolar proteins from Golgi apparatus or trans-Golgi network （TGN） to vacuoles is a receptor-mediated process via an intermediate membrane-bound prevacuolar compartment （PVC） in plant cells. Both vacuolar sorting receptor （VSR） and receptor homology region-transmembrane domain-RING-H2 （RMR） proteins have been shown to function in transporting storage proteins to protein storage vacuole （PSV）, but little is known about the nature of the PVC for the PSV pathway. Here, we use the rice RMR1 （OsRMR1） as a probe to study the PSV pathway in plants. Immunogold electron microscopy （EM） with specific OsRMR1 antibodies showed that OsRMR1 proteins were found in the Golgi apparatus, TGN, and a distinct organelle with characteristics of PVC in both rice culture cells and developing rice seeds, as well as the protein body type II （PBII） or PSV in developing rice seeds. This organelle, also found in both tobacco BY-2 and Arabidopsis suspension cultured cells, is morphologically distinct from the VSR-positive multivesicular lytic PVC or multivesicular body （MVB） and thus represent a PVC for the PSV pathway that we name storage PVC （sPVC）. Further in vivo and in vitro interaction studies using truncated OsRMR1 proteins secreted into the culture media of transgenic BY-2 suspension cells demonstrated that OsRMR1 functions as a sorting receptor in transporting vicilin-like storage proteins.展开更多
Prevacuolar compartments （PVCs） and endosomal compartments are membrane-bound organelles mediating protein traffic to vacuoles in the secretory and endocytic pathways of plant cells. Over the years, great progress h...Prevacuolar compartments （PVCs） and endosomal compartments are membrane-bound organelles mediating protein traffic to vacuoles in the secretory and endocytic pathways of plant cells. Over the years, great progress has been made towards our understanding in these two compartments in plant cells. In this review, we will summarize our contributions toward the identification and characterization of plant prevacuolar and endosomal compartments. Our studies will serve as important steps in future molecular characterization of PVC biogenesis and PVC-mediated protein traffickinq in plant cells.展开更多
文摘Vacuolar sorting receptors （VSRs） are type I integral membrane proteins that mediate the vacuolar transport of soluble cargo proteins via prevacuolar compartments （PVCs） in plants. Confocal immunofluorescent and immunogold Electron Microscope （EM） studies have localized VSRs to PVCs or multivesicular bodies （MVBs） and trans-Golgi network （TGN） in various plant cell types, including suspension culture cells, root cells, developing and germinating seeds. Here, we provide evidence that VSRs reach plasma membrane （PM） in growing pollen tubes. Both immunofluorescent and immunogold EM studies with specific VSR antibodies show that, in addition to the previously demonstrated PVC/MVB localization, VSRs also localize to PM in lily and tobacco pollen tubes prepared from chemical fixation or high-pressure freezing/frozen substitution. Such a PM localization suggests an additional role of VSR proteins in mediating protein transport to PM and endocytosis in growing pollen tubes. Using a high-speed Spinning Disc Confocal Microscope, the possible fusion between VSR-positive PVC organelles and the PM was also observed in living tobacco pollen tubes transiently expressing the PVC reporter GFP-VSR. In contrast, the lack of a prominent PM localization of GFP-VSR in living pollen tubes may be due to the highly dynamic situation of vesicular transport in this fast-growing cell type.
文摘Plant prevacuolar compartments （PVCs）, or multivesicular bodies （MVBs）, are single membrane-bound organelles that play important roles in mediating protein trafficking to vacuoles in the secretory pathway. PVC/MVB also serves as a late endosome in the endocytic pathway in plants. Since the plant PVC was iden- tified as an MVB more than 10 years ago,-great progress has been made toward the understanding of PVC/ MVB function and biogenesis in plants. In this review, we first summarize previous research into the iden- tification and characterization of plant PVCs/MVBs, and then highlight recent advances on the mechanisms underlying intraluminal vesicle formation and maturation of plant PVCs/MVBs. In addition, we discuss the possible crosstalk that appears to occur between PVCs/MVBs and autophagosomes during autophagy in plants. Finally, we list some open questions and present future perspectives in this field.
文摘Transport of vacuolar proteins from Golgi apparatus or trans-Golgi network （TGN） to vacuoles is a receptor-mediated process via an intermediate membrane-bound prevacuolar compartment （PVC） in plant cells. Both vacuolar sorting receptor （VSR） and receptor homology region-transmembrane domain-RING-H2 （RMR） proteins have been shown to function in transporting storage proteins to protein storage vacuole （PSV）, but little is known about the nature of the PVC for the PSV pathway. Here, we use the rice RMR1 （OsRMR1） as a probe to study the PSV pathway in plants. Immunogold electron microscopy （EM） with specific OsRMR1 antibodies showed that OsRMR1 proteins were found in the Golgi apparatus, TGN, and a distinct organelle with characteristics of PVC in both rice culture cells and developing rice seeds, as well as the protein body type II （PBII） or PSV in developing rice seeds. This organelle, also found in both tobacco BY-2 and Arabidopsis suspension cultured cells, is morphologically distinct from the VSR-positive multivesicular lytic PVC or multivesicular body （MVB） and thus represent a PVC for the PSV pathway that we name storage PVC （sPVC）. Further in vivo and in vitro interaction studies using truncated OsRMR1 proteins secreted into the culture media of transgenic BY-2 suspension cells demonstrated that OsRMR1 functions as a sorting receptor in transporting vicilin-like storage proteins.
基金Supported by grants from the Research Grants Council of Hong Kong(CUHK4156/01M,CUHK4260/02M,CUHK4307/03M,and CUHK4580/05M)National Science Foundation of China (30529001)+1 种基金CUHK Scheme C,UGCAoE(B-07/99)Germany/HK Joint Research Scheme to L.Jiang.
文摘Prevacuolar compartments （PVCs） and endosomal compartments are membrane-bound organelles mediating protein traffic to vacuoles in the secretory and endocytic pathways of plant cells. Over the years, great progress has been made towards our understanding in these two compartments in plant cells. In this review, we will summarize our contributions toward the identification and characterization of plant prevacuolar and endosomal compartments. Our studies will serve as important steps in future molecular characterization of PVC biogenesis and PVC-mediated protein traffickinq in plant cells.
