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
Callose,aβ-1,3-glucan plant cell wall polymer,regulates symplasmic channel size at plasmodesmata(PD)and plays a crucial role in a variety of plant processes.However,elucidating the molecular mechanism of PD callose h...Callose,aβ-1,3-glucan plant cell wall polymer,regulates symplasmic channel size at plasmodesmata(PD)and plays a crucial role in a variety of plant processes.However,elucidating the molecular mechanism of PD callose homeostasis is limited.We screened and identified an Arabidopsis mutant plant with excessive callose deposition at PD and found that the mutated gene wasα1-COP,a member of the coat protein I(COPI)coatomer complex.We report that loss of function ofα1-COP elevates the callose accumulation at PD by affecting subcellular protein localization of callose degradation enzyme Pd BG2.This process is linked to the functions of ERH1,an inositol phosphoryl ceramide synthase,and glucosylceramide synthase through physical interactions with theα1-COP protein.Additionally,the loss of function ofα1-COP alters the subcellular localization of ERH1 and GCS proteins,resulting in a reduction of Glc Cers and Glc HCers molecules,which are key sphingolipid(SL)species for lipid raft formation.Our findings suggest thatα1-COP protein,together with SL modifiers controlling lipid raft compositions,regulates the subcellular localization of GPI-anchored PDBG2 proteins,and hence the callose turnover at PD and symplasmic movement of biomolecules.Our findings provide the first key clue to link the COPI-mediated intracellular trafficking pathway to the callose-mediated intercellular signaling pathway through PD.展开更多
The microdomains of plasmodesmata,specialized cell-wall channels responsible for communications between neighboring cells,are composed of various plasmodesmata-located proteins(PDLPs)and lipids.Here,we found that,amon...The microdomains of plasmodesmata,specialized cell-wall channels responsible for communications between neighboring cells,are composed of various plasmodesmata-located proteins(PDLPs)and lipids.Here,we found that,among all PDLP or homologous proteins in Arabidopsis thaliana genome,PDLP5 and PDLP7 possessed a C-terminal sphingolipid-binding motif,with the latter being the only member that was significantly upregulated upon turnip mosaic virus and cucumber mosaic virus infections.pdlp7mutant plants exhibited significantly reduced callose deposition,larger plasmodesmata diameters,and faster viral transmission.These plants exhibited increased glucosidase activity but no change in callose synthase activity.PDLP7 interacted specifically with glucan endo-1,3-β-glucosidase 10(BG10).Consistently,higher levels of callose deposition and slower virus transmission in bg10 mutants were observed.The interaction between PDLP7 and BG10 was found to depend on the presence of the Gnk2-homologous 1(Gn K2-1)domain at the N terminus of PDLP7 with Asp-35,Cys-42,Gln-44,and Leu-116 being essential.In vitro supplementation of callose was able to change the conformation of the Gn K2-1 domain.Our data suggest that the Gn K2-1 domain of PDLP7,in conjunction with callose and BG10,plays a key role in plasmodesmata opening and closure,which is necessary for intercellular movement of various molecules.展开更多
Pathogens use effector proteins to manipulate their hosts. During infection of tomato, the fungus Fusarium oxysporum secretes the effectors Avr2 and Six5. Whereas Avr2 suffices to trigger I-2-mediated cell death in he...Pathogens use effector proteins to manipulate their hosts. During infection of tomato, the fungus Fusarium oxysporum secretes the effectors Avr2 and Six5. Whereas Avr2 suffices to trigger I-2-mediated cell death in heterologous systems, both effectors are required for I-2-mediated disease resistance in tomato. How Six5 participates in triggering resistance is unknown. Using bimolecular fluorescence complementation assays we found that Avr2 and Six5 interact at plasmodesmata. Single-cell transformation revealed that a 2xRFP marker protein and Avr2-GFP only move to neighboring cells in the presence of Six5. Six5 alone does not alter plasmodesmatal transduction as 2xRFP was only translocated in the presence of both effectors. In SIX5-expressing transgenic plants, the distribution of virally expressed Avr2-GFP, and subsequent onset of I-2-mediated cell death, differed from that in wild-type tomato. Taken together, our data show that in the presence of Six5, Avr2 moves from cell to cell, which in susceptible plants contributes to virulence, but in I-2 containing plants induces resistance.展开更多
Plant plasmodesmata (PDs) are specialized channels that enable communication between neighboring cells. The intercellular permeability of PDs, which affects plant development, defense, and responses to stimuli, must b...Plant plasmodesmata (PDs) are specialized channels that enable communication between neighboring cells. The intercellular permeability of PDs, which affects plant development, defense, and responses to stimuli, must be tightly regulated. However, the lipid compositions of PD membrane and their impact on PD permeability remain elusive. Here, we report that the Arabidopsis sld1 sld2 double mutant, lacking sphingolipid long-chain base 8 desaturases 1 and 2, displayed decreased PD permeability due to a significant increase in callose accumulation. PD-located protein 5 (PDLP5) was significantly enriched in the leaf epidermal cells of sld1 sld2 and showed specific binding affinity to phytosphinganine (t18:0), suggesting that the enrichment of t18:0-based sphingolipids in sld1 sld2 PDs might facilitate the recruitment of PDLP5 proteins to PDs. The sld1 sld2 double mutant seedlings showed enhanced resistance to the fungal-wilt pathogen Verticillium dahlia and the bacterium Pseudomonas syringae pv. tomato DC3000, which could be fully rescued in sld1 sld2 pdlp5 triple mutant . Taken together, these results indicate that phytosphinganine might regulate PD functions and cell-to-cell communication by modifying the level of PDLP5 in PD membranes.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.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea Government(MSIT)(Grant Nos.NRF 2018R1A2A1A05077295,2020M3A9I4038352,2022R1A2C3010331,2020R1A6A1A03044344,and 2022R1A 5A1031361)a grant from the New Breeding Technologies Development Program(Grant No.PJ01653202),Rural Development Administration(RDA),Republic of Korea。
文摘Callose,aβ-1,3-glucan plant cell wall polymer,regulates symplasmic channel size at plasmodesmata(PD)and plays a crucial role in a variety of plant processes.However,elucidating the molecular mechanism of PD callose homeostasis is limited.We screened and identified an Arabidopsis mutant plant with excessive callose deposition at PD and found that the mutated gene wasα1-COP,a member of the coat protein I(COPI)coatomer complex.We report that loss of function ofα1-COP elevates the callose accumulation at PD by affecting subcellular protein localization of callose degradation enzyme Pd BG2.This process is linked to the functions of ERH1,an inositol phosphoryl ceramide synthase,and glucosylceramide synthase through physical interactions with theα1-COP protein.Additionally,the loss of function ofα1-COP alters the subcellular localization of ERH1 and GCS proteins,resulting in a reduction of Glc Cers and Glc HCers molecules,which are key sphingolipid(SL)species for lipid raft formation.Our findings suggest thatα1-COP protein,together with SL modifiers controlling lipid raft compositions,regulates the subcellular localization of GPI-anchored PDBG2 proteins,and hence the callose turnover at PD and symplasmic movement of biomolecules.Our findings provide the first key clue to link the COPI-mediated intracellular trafficking pathway to the callose-mediated intercellular signaling pathway through PD.
基金supported by the National Natural Science Foundation of China(31830057)。
文摘The microdomains of plasmodesmata,specialized cell-wall channels responsible for communications between neighboring cells,are composed of various plasmodesmata-located proteins(PDLPs)and lipids.Here,we found that,among all PDLP or homologous proteins in Arabidopsis thaliana genome,PDLP5 and PDLP7 possessed a C-terminal sphingolipid-binding motif,with the latter being the only member that was significantly upregulated upon turnip mosaic virus and cucumber mosaic virus infections.pdlp7mutant plants exhibited significantly reduced callose deposition,larger plasmodesmata diameters,and faster viral transmission.These plants exhibited increased glucosidase activity but no change in callose synthase activity.PDLP7 interacted specifically with glucan endo-1,3-β-glucosidase 10(BG10).Consistently,higher levels of callose deposition and slower virus transmission in bg10 mutants were observed.The interaction between PDLP7 and BG10 was found to depend on the presence of the Gnk2-homologous 1(Gn K2-1)domain at the N terminus of PDLP7 with Asp-35,Cys-42,Gln-44,and Leu-116 being essential.In vitro supplementation of callose was able to change the conformation of the Gn K2-1 domain.Our data suggest that the Gn K2-1 domain of PDLP7,in conjunction with callose and BG10,plays a key role in plasmodesmata opening and closure,which is necessary for intercellular movement of various molecules.
文摘Pathogens use effector proteins to manipulate their hosts. During infection of tomato, the fungus Fusarium oxysporum secretes the effectors Avr2 and Six5. Whereas Avr2 suffices to trigger I-2-mediated cell death in heterologous systems, both effectors are required for I-2-mediated disease resistance in tomato. How Six5 participates in triggering resistance is unknown. Using bimolecular fluorescence complementation assays we found that Avr2 and Six5 interact at plasmodesmata. Single-cell transformation revealed that a 2xRFP marker protein and Avr2-GFP only move to neighboring cells in the presence of Six5. Six5 alone does not alter plasmodesmatal transduction as 2xRFP was only translocated in the presence of both effectors. In SIX5-expressing transgenic plants, the distribution of virally expressed Avr2-GFP, and subsequent onset of I-2-mediated cell death, differed from that in wild-type tomato. Taken together, our data show that in the presence of Six5, Avr2 moves from cell to cell, which in susceptible plants contributes to virulence, but in I-2 containing plants induces resistance.
基金This research was supported by grants from the National Science and Technology Major Project(2016ZX08010-001)the National Natural Science Foundation of China(31570283).
文摘Plant plasmodesmata (PDs) are specialized channels that enable communication between neighboring cells. The intercellular permeability of PDs, which affects plant development, defense, and responses to stimuli, must be tightly regulated. However, the lipid compositions of PD membrane and their impact on PD permeability remain elusive. Here, we report that the Arabidopsis sld1 sld2 double mutant, lacking sphingolipid long-chain base 8 desaturases 1 and 2, displayed decreased PD permeability due to a significant increase in callose accumulation. PD-located protein 5 (PDLP5) was significantly enriched in the leaf epidermal cells of sld1 sld2 and showed specific binding affinity to phytosphinganine (t18:0), suggesting that the enrichment of t18:0-based sphingolipids in sld1 sld2 PDs might facilitate the recruitment of PDLP5 proteins to PDs. The sld1 sld2 double mutant seedlings showed enhanced resistance to the fungal-wilt pathogen Verticillium dahlia and the bacterium Pseudomonas syringae pv. tomato DC3000, which could be fully rescued in sld1 sld2 pdlp5 triple mutant . Taken together, these results indicate that phytosphinganine might regulate PD functions and cell-to-cell communication by modifying the level of PDLP5 in PD membranes.
