The characters and ultrastructure of the intercellular connection were revealed in the outer epidermis of the garlic clove sheath by means of fluorescent probe TRITC_Phalloidin (TRITC_Ph) labeling combined with confoc...The characters and ultrastructure of the intercellular connection were revealed in the outer epidermis of the garlic clove sheath by means of fluorescent probe TRITC_Phalloidin (TRITC_Ph) labeling combined with confocal laser scanning microscopy (CLSM), immuno_gold labeling and transmission electron microscopy. These results show that transcellular channel is a complex of rod_like cytoplasm channel and grouped plasmodesmata (PDs) in pit. The former remains a portion of the cell protoplast. The diameter of PD is normally 60-70 nm. The PDs are the real intercellular symplasmic connections of the cells. The transcellular fibers labeled with the TRITC_Ph obviously become narrow in the primary pit fields, which is the same as the characters observed under the electron microscope. The bright fluorescent spot in the primary wall reflects the grouped PDs in pit, and hence the presence of F_actin in the PDs can be confirmed. In immuno_gold labeling experiment, a lot of gold particles were massively distributed in the rod_like cytoplasm channel and grouped PDs. The result provides effective support that these fluorescent filaments possibly are the existing form of F_actin.展开更多
With light and electron microscopy the substructural change and the ATPase activity of corn (Zea mays L.) root cap cells after short-term osmotic stress were studied. Some spoke-like fine strands originating from the ...With light and electron microscopy the substructural change and the ATPase activity of corn (Zea mays L.) root cap cells after short-term osmotic stress were studied. Some spoke-like fine strands originating from the departed periplasm and stretching towards cell wall could be observed even after plasmolysis. By observing the precipitation of ATPase activity product (lead phosphate) at plasma membrane and plasmodesmata, it was found that the fine strands were plasma membrane-lined channels surrounding the cytoplasm and that they still firmly connected to the plasmodesmata during plasmolysis. Compared with the control (unstressed), a sharp decrease of ATPase activity in the plasmodesmata of the stressed cells was observed. Inhibition of energy metabolism in these limited locales would affect the physiological activity, maybe including the regulation of permeability and the change of size exclusion limit (SEL) of plasmodesmata.展开更多
Plasmodesmata (PDs) are cytoplasmic structures that link adjacent cells to form the symplast of a plant. PDs are involved extensively in a plant's life by mediating symplastic transport of a wide range of ions and...Plasmodesmata (PDs) are cytoplasmic structures that link adjacent cells to form the symplast of a plant. PDs are involved extensively in a plant's life by mediating symplastic transport of a wide range of ions and molecules. Major components of a plasmodesma (PD) include a plasma membrane, a desmotubule, and a cytoplasmic annulus, all of which are readily detectable by electron microscopy. Both the plasma membrane and the desmotubule contain proteinaceous particles, thought to be involved in altering the size of the cytoplasmic annulus. Cytoskeleton elements (actin and myosin) are essential for maintaining the integrity of PDs. Together with these elements, calcium_binding proteins probably play a significant role in regulating PD function. Symplastic transport occurs through the cytoplasmic annulus for the great majority of solutes, while other substances may traverse through the desmotubule internal compartment, the desmotubule shell, or the plasma membrane. The symplast is subdivided into several domains with varying molecular size exclusion limits (ranging from <1 kD to >10 kD). Plasmodesmata can be either primary or secondary; the former are developed during new wall formation and the latter are made in existing walls. The dynamic nature of plasmodesmata is also reflected by their changing frequencies, which, in turn, depend on the developmental and physiological status of the tissue or the entire plant. While diffusion is the major mechanism of symplastic transport, plasmodesmata are selective for certain ions and molecules. Upon viral infection, viral movement proteins interact with PD receptor proteins and, as a result of yet unknown mechanisms, the plasmodesmata are remarkably dilated to allow viral movement proteins and the bound viral genome to enter healthy cells. Some proteins of plant origin are also able to traverse plasmodesmata, presumably in ways similar to viral movement proteins. Some of these plant proteins are probably signal molecules contributing to cell differentiation and other activities. Other proteins move cell_to_cell in a non_specific manner.展开更多
Actin and myosin were found to be associated with the cytoplasmic sleeve of plasmodesmata. As cytoskeletal proteins, actin and myosin are believed to regulate the conductivity of plasmodesmata （PDs） in higher plants...Actin and myosin were found to be associated with the cytoplasmic sleeve of plasmodesmata. As cytoskeletal proteins, actin and myosin are believed to regulate the conductivity of plasmodesmata （PDs） in higher plants. Using immunocytochemical methods, we found the two proteins to be co-localized - and closely linked to each other - in plasmodesmata and ectodesmata-like structure in ageing parenchymatous cells of Allium sativum L. We suggest that intercellular communication is affected by the interaction between actin and myosin.展开更多
Pectinase activity was localized at the ultrastructural level in pollen mother cells of tobacco(Nicotiana tabacum L.)during meiotic prophase I to elucidate its role in the biogenesis of secondary plasmodesma(sPD)and c...Pectinase activity was localized at the ultrastructural level in pollen mother cells of tobacco(Nicotiana tabacum L.)during meiotic prophase I to elucidate its role in the biogenesis of secondary plasmodesma(sPD)and cytoplasmic channel(CC).At the leptotene stage the enzyme was mainly present in the cisternae of smooth endoplasmic reticulum(SER)and their derived vesicles,but absent in the Golgi body and Golgi vesicles.Later at the zygotene stage,when sPDs and CCs were actively formed,strong pectinase activity was observed not only in the SER cisternae and their derived vesicles but also in the cell wall,especially in the vicinity of or within both simple and branched plasmodesmata,notably along the middle lamellae,which also characterized the sites of CCs being formed.The presence of exocytotic vesicles containing reaction products suggests that pectinase shares the same excretive pathway as that used by cellulase for its delivery into the wall,i.e.in active form via smooth endoplasmic reticulum(ER)and its derived vesicles by exocytosis.In combination with cellulase,pectinase also promotes the secondaryformation of plasmodesmata and CCs by specifically digesting the pectin in middle lamella.展开更多
Cytoplasmic bridge,as a broader cellular connection structure,exists in plants from Vo/vox to higher plants,but has been subjected to less investigation as compared to plasmodesmata.It has been speculated that the str...Cytoplasmic bridge,as a broader cellular connection structure,exists in plants from Vo/vox to higher plants,but has been subjected to less investigation as compared to plasmodesmata.It has been speculated that the structure may be related to the synchronization of cell division and development during the microsporegenesis and spermatogenesis.During spermatogenesis in bryophytes,the spermatogenous cells are divided into several domains within an antheridium,and their divisions are synchronous.However,their cellular connection system has not been investigated systematically.In this study,we undertook an ultrastructural examination of the structure and dynamics of the intercellular connection system during the spermatogenesis in Funaria hygrometrica Hedw.The result revealed that within each individual domain,synchronously dividing spermatogenous cells were connected with each other by numerous cytoplasmic bridges,which were absent in the walls between different domains.The plasmodesmata connected spermatogenous cells with the cells of jacket layer,and also existed between the jacket layer cells,but absent in the walls between the developing spermatogenous cells.At the latestage of the an theridial development,as the cell wall began to degrade,all of the spermatid cells within anantheridium seem connected with each other by the expanded cytoplasmic bridges.The cytoplasmic bridges retained to the late stage of spermatid's differentiation,and finally,the spermatids synchronously differentiated into spermatozoids.The different internal structures,biogenesis mechanisms and distribution between the plasmodesmata and cytoplasmic bridges suggest that they may play distinct roles during the development of antheridia.展开更多
Cell-to-cell communication is fundamental to multicellular life.In plants,plasmodesmata—cytoplasmic channels that connect adjacent cells—enable the transport of molecules between cells.In roots,such transport is tho...Cell-to-cell communication is fundamental to multicellular life.In plants,plasmodesmata—cytoplasmic channels that connect adjacent cells—enable the transport of molecules between cells.In roots,such transport is thought to play a central role in nutrient acquisition and delivery across the multiple cell layers.In this study,we demonstrate that plasmodesmatal transport persists in fully differentiated Arabidopsis roots,even after the establishment of apoplastic barriers such as Casparian strips and suberin lamellae in the endodermis.This persistence highlights plasmodesmata as a critical pathway for intercellular transport in mature roots.We also identify a developmental switch in plasmodesmatal function:while transport is bidirectional in young roots,it becomes unidirectional toward the vasculature in differentiated roots.Through a genetic screen,we identified mutants with impaired directionality that maintain persistent bidirectional transport.These mutants show enlarged plasmodesmatal apertures due to defects in pectin composition and cell wall organization,highlighting the critical role of pectin in plasmodesmatal formation and function.Our findings reveal that plasmodesmata-mediated transport is dynamically regulated during root development and provide new insights into the cellular mechanisms underlying intercellular communication in plants.展开更多
Plasmodesmata(PD)create symplasmic continuity in plant tissues by connecting the cytoplasm of neighboring cells.Molecular movement through PD is important for many processes,including organ development,pathogen defens...Plasmodesmata(PD)create symplasmic continuity in plant tissues by connecting the cytoplasm of neighboring cells.Molecular movement through PD is important for many processes,including organ development,pathogen defense,environmental acclimation,and nutrient allocation.Elucidating the kinetics of PD transport and its regulation is essential for understanding these processes.展开更多
文摘The characters and ultrastructure of the intercellular connection were revealed in the outer epidermis of the garlic clove sheath by means of fluorescent probe TRITC_Phalloidin (TRITC_Ph) labeling combined with confocal laser scanning microscopy (CLSM), immuno_gold labeling and transmission electron microscopy. These results show that transcellular channel is a complex of rod_like cytoplasm channel and grouped plasmodesmata (PDs) in pit. The former remains a portion of the cell protoplast. The diameter of PD is normally 60-70 nm. The PDs are the real intercellular symplasmic connections of the cells. The transcellular fibers labeled with the TRITC_Ph obviously become narrow in the primary pit fields, which is the same as the characters observed under the electron microscope. The bright fluorescent spot in the primary wall reflects the grouped PDs in pit, and hence the presence of F_actin in the PDs can be confirmed. In immuno_gold labeling experiment, a lot of gold particles were massively distributed in the rod_like cytoplasm channel and grouped PDs. The result provides effective support that these fluorescent filaments possibly are the existing form of F_actin.
基金Supported by the grants from the National Natural Science Foundation of China.
文摘With light and electron microscopy the substructural change and the ATPase activity of corn (Zea mays L.) root cap cells after short-term osmotic stress were studied. Some spoke-like fine strands originating from the departed periplasm and stretching towards cell wall could be observed even after plasmolysis. By observing the precipitation of ATPase activity product (lead phosphate) at plasma membrane and plasmodesmata, it was found that the fine strands were plasma membrane-lined channels surrounding the cytoplasm and that they still firmly connected to the plasmodesmata during plasmolysis. Compared with the control (unstressed), a sharp decrease of ATPase activity in the plasmodesmata of the stressed cells was observed. Inhibition of energy metabolism in these limited locales would affect the physiological activity, maybe including the regulation of permeability and the change of size exclusion limit (SEL) of plasmodesmata.
文摘Plasmodesmata (PDs) are cytoplasmic structures that link adjacent cells to form the symplast of a plant. PDs are involved extensively in a plant's life by mediating symplastic transport of a wide range of ions and molecules. Major components of a plasmodesma (PD) include a plasma membrane, a desmotubule, and a cytoplasmic annulus, all of which are readily detectable by electron microscopy. Both the plasma membrane and the desmotubule contain proteinaceous particles, thought to be involved in altering the size of the cytoplasmic annulus. Cytoskeleton elements (actin and myosin) are essential for maintaining the integrity of PDs. Together with these elements, calcium_binding proteins probably play a significant role in regulating PD function. Symplastic transport occurs through the cytoplasmic annulus for the great majority of solutes, while other substances may traverse through the desmotubule internal compartment, the desmotubule shell, or the plasma membrane. The symplast is subdivided into several domains with varying molecular size exclusion limits (ranging from <1 kD to >10 kD). Plasmodesmata can be either primary or secondary; the former are developed during new wall formation and the latter are made in existing walls. The dynamic nature of plasmodesmata is also reflected by their changing frequencies, which, in turn, depend on the developmental and physiological status of the tissue or the entire plant. While diffusion is the major mechanism of symplastic transport, plasmodesmata are selective for certain ions and molecules. Upon viral infection, viral movement proteins interact with PD receptor proteins and, as a result of yet unknown mechanisms, the plasmodesmata are remarkably dilated to allow viral movement proteins and the bound viral genome to enter healthy cells. Some proteins of plant origin are also able to traverse plasmodesmata, presumably in ways similar to viral movement proteins. Some of these plant proteins are probably signal molecules contributing to cell differentiation and other activities. Other proteins move cell_to_cell in a non_specific manner.
基金supported by the National Natural Science Foundation of China (30070365, 30470861, 30971706)the Natural Science Foundation of Hebei Province, China (C2008000321)the Specialized Research Fund for the Doctoral Program of Higher Education, China (20060086003)
文摘Actin and myosin were found to be associated with the cytoplasmic sleeve of plasmodesmata. As cytoskeletal proteins, actin and myosin are believed to regulate the conductivity of plasmodesmata （PDs） in higher plants. Using immunocytochemical methods, we found the two proteins to be co-localized - and closely linked to each other - in plasmodesmata and ectodesmata-like structure in ageing parenchymatous cells of Allium sativum L. We suggest that intercellular communication is affected by the interaction between actin and myosin.
文摘Pectinase activity was localized at the ultrastructural level in pollen mother cells of tobacco(Nicotiana tabacum L.)during meiotic prophase I to elucidate its role in the biogenesis of secondary plasmodesma(sPD)and cytoplasmic channel(CC).At the leptotene stage the enzyme was mainly present in the cisternae of smooth endoplasmic reticulum(SER)and their derived vesicles,but absent in the Golgi body and Golgi vesicles.Later at the zygotene stage,when sPDs and CCs were actively formed,strong pectinase activity was observed not only in the SER cisternae and their derived vesicles but also in the cell wall,especially in the vicinity of or within both simple and branched plasmodesmata,notably along the middle lamellae,which also characterized the sites of CCs being formed.The presence of exocytotic vesicles containing reaction products suggests that pectinase shares the same excretive pathway as that used by cellulase for its delivery into the wall,i.e.in active form via smooth endoplasmic reticulum(ER)and its derived vesicles by exocytosis.In combination with cellulase,pectinase also promotes the secondaryformation of plasmodesmata and CCs by specifically digesting the pectin in middle lamella.
文摘Cytoplasmic bridge,as a broader cellular connection structure,exists in plants from Vo/vox to higher plants,but has been subjected to less investigation as compared to plasmodesmata.It has been speculated that the structure may be related to the synchronization of cell division and development during the microsporegenesis and spermatogenesis.During spermatogenesis in bryophytes,the spermatogenous cells are divided into several domains within an antheridium,and their divisions are synchronous.However,their cellular connection system has not been investigated systematically.In this study,we undertook an ultrastructural examination of the structure and dynamics of the intercellular connection system during the spermatogenesis in Funaria hygrometrica Hedw.The result revealed that within each individual domain,synchronously dividing spermatogenous cells were connected with each other by numerous cytoplasmic bridges,which were absent in the walls between different domains.The plasmodesmata connected spermatogenous cells with the cells of jacket layer,and also existed between the jacket layer cells,but absent in the walls between the developing spermatogenous cells.At the latestage of the an theridial development,as the cell wall began to degrade,all of the spermatid cells within anantheridium seem connected with each other by the expanded cytoplasmic bridges.The cytoplasmic bridges retained to the late stage of spermatid's differentiation,and finally,the spermatids synchronously differentiated into spermatozoids.The different internal structures,biogenesis mechanisms and distribution between the plasmodesmata and cytoplasmic bridges suggest that they may play distinct roles during the development of antheridia.
基金supported by iGe3 with a PhD salary award to L.J.,and by funding from the Sandoz Family Monique De Meuron philanthropic foundation's program for academic promotionby the Swiss National Science Foundation(grant 31003A_179159)to M.B.by the state of Geneva.
文摘Cell-to-cell communication is fundamental to multicellular life.In plants,plasmodesmata—cytoplasmic channels that connect adjacent cells—enable the transport of molecules between cells.In roots,such transport is thought to play a central role in nutrient acquisition and delivery across the multiple cell layers.In this study,we demonstrate that plasmodesmatal transport persists in fully differentiated Arabidopsis roots,even after the establishment of apoplastic barriers such as Casparian strips and suberin lamellae in the endodermis.This persistence highlights plasmodesmata as a critical pathway for intercellular transport in mature roots.We also identify a developmental switch in plasmodesmatal function:while transport is bidirectional in young roots,it becomes unidirectional toward the vasculature in differentiated roots.Through a genetic screen,we identified mutants with impaired directionality that maintain persistent bidirectional transport.These mutants show enlarged plasmodesmatal apertures due to defects in pectin composition and cell wall organization,highlighting the critical role of pectin in plasmodesmatal formation and function.Our findings reveal that plasmodesmata-mediated transport is dynamically regulated during root development and provide new insights into the cellular mechanisms underlying intercellular communication in plants.
文摘Plasmodesmata(PD)create symplasmic continuity in plant tissues by connecting the cytoplasm of neighboring cells.Molecular movement through PD is important for many processes,including organ development,pathogen defense,environmental acclimation,and nutrient allocation.Elucidating the kinetics of PD transport and its regulation is essential for understanding these processes.
