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
The plant sucrose transporter SUT1 （from Solanum tuberosum, S. lycopersicum, or Zea mays） exhibits redoxdependent dimerization and targeting if heterologously expressed in S. cerevisiae （Krtigel et al., 2008）. It ...The plant sucrose transporter SUT1 （from Solanum tuberosum, S. lycopersicum, or Zea mays） exhibits redoxdependent dimerization and targeting if heterologously expressed in S. cerevisiae （Krtigel et al., 2008）. It was also shown that SUT1 is present in motile vesicles when expressed in tobacco cells and that its targeting to the plasma membrane is reversible. StSUT1 is internalized in the presence of brefeldin A （BFA） in yeast, plant cells, and in mature sieve elements as confirmed by immunolocalization. These results were confirmed here and the dynamics of intracellular SUT1 localization were further elucidated. Inhibitor studies revealed that vesicle movement of SUT1 is actin-dependent. BFA-mediated effects might indicate that anterograde vesicle movement is possible even in mature sieve elements, and could involve components of the cytoskeleton that were previously thought to be absent in SEs. Our results are in contradiction to this old dogma of plant physiology and the potential of mature sieve elements should therefore be re-evaluated. In addition, SUT1 internalization was found to be dependent on the plasma membrane lipid composition. SUT1 belongs to the detergent-resistant membrane （DRM） fraction in planta and is targeted to membrane raft-like microdomains when expressed in yeast （Kr（igel et al,, 2008）, Here, SUT1-GFP expression in different yeast mutants, which were unable to perform en- docytosis and/or raft formation, revealed a strong link between SUT1 raft localization, the sterol composition and mem- brane potential of the yeast plasma membrane, and the capacity of the SUT1 protein to be internalized by endocytosis. The results provide new insight into the regulation of sucrose transport and the mechanism of endocytosis in plant cells.展开更多
In the phloem cap region o i Arabidopsis plants,sulfur-rich cells(S-cells)accumulate>100 mM glucosinolates(GLS),but are biosynthetically inactive.The source and route of S-cell-bound GLS remain elusive.In this stud...In the phloem cap region o i Arabidopsis plants,sulfur-rich cells(S-cells)accumulate>100 mM glucosinolates(GLS),but are biosynthetically inactive.The source and route of S-cell-bound GLS remain elusive.In this study,using single-cell sampling and scanning electron microscopy with energy-dispersive X-ray analysis we show that two GLS importers,NPF2.10/GTR1 and NPF2.11/GTR2,are critical for GLS accumulation in S-cells,although they are not localized in the S-cells.Comparison of GLS levels in S-cells in multiple combinations of homo-and heterografts o lg t r l gtr2,biosynthetic null mutant and wild-type plants indicate that S-cells accumulate GLS via symplasmic connections either directly from neighboring biosynthetic cells or indirectly to non-neighboring cells expressing GTR1/2.Distinct sources and transport routes exist for different types of GLS,and vary depending on the position of S-cells in the inflorescence stem.Based on these findings,we propose a model illustrating the GLS transport routes either directly from biosynthetic cells or via GTR-mediated import from apoplastic space radially into a symplasmic domain,wherein the S-cells are the ultimate sink.Similarly,we observed accumulation of the cyanogenic glucoside defensive compounds in high-turgor cells in the phloem cap of Lotus japonicus,suggesting that storage of defensive compounds in high-turgor cells may be a general mechanism for chemical protection of the phloem cap.展开更多
Background:Acute-onset neurodegenerative diseases in older patients are rare clinical cases,especially when the degeneration only affects specific regions of the nervous system.Several neurological disorders have been...Background:Acute-onset neurodegenerative diseases in older patients are rare clinical cases,especially when the degeneration only affects specific regions of the nervous system.Several neurological disorders have been described in which the degeneration of brain parenchyma originates from and/or primarily affects the brain stem.Clinical diagnosis in these patients,however,is often complicated due to a poor understanding of these diseases and their underlying mechanisms.Case presentation:In this manuscript we report on a 73-year-old female who had experienced a sudden onset of complex neurological symptoms that progressively worsened over a period of 2 years.Original evaluation had suggested a MRI-negative stroke as underlying pathogenesis.The combination of patient’s medical history,clinical examination and exceptional pattern of brain stem degeneration presenting as“kissing swan sign”in MR imaging was strongly suggestive of acute onset of Alexander’s disease.This leukoencephalopathy is caused by GFAP(glial fibrilary acidic protein)gene mutations and may present with brain stem atrophy and stroke-like onset of symptoms in elderly individuals.However,a pathognomonic GFAP gene mutation could not be identified by Sanger sequencing.Conclusions:After an extended differential diagnosis and exclusion of other diseases,a definite diagnosis of the patient’s condition presently remains elusive.However,whole-exome sequencing performed from patient’s blood revealed 12 potentially disease-causative heterozygous variants,amongst which several have been associated with neurological disorders in vitro and in vivo–in particular the axon degeneration-related NMNAT2 gene.展开更多
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.
文摘The plant sucrose transporter SUT1 （from Solanum tuberosum, S. lycopersicum, or Zea mays） exhibits redoxdependent dimerization and targeting if heterologously expressed in S. cerevisiae （Krtigel et al., 2008）. It was also shown that SUT1 is present in motile vesicles when expressed in tobacco cells and that its targeting to the plasma membrane is reversible. StSUT1 is internalized in the presence of brefeldin A （BFA） in yeast, plant cells, and in mature sieve elements as confirmed by immunolocalization. These results were confirmed here and the dynamics of intracellular SUT1 localization were further elucidated. Inhibitor studies revealed that vesicle movement of SUT1 is actin-dependent. BFA-mediated effects might indicate that anterograde vesicle movement is possible even in mature sieve elements, and could involve components of the cytoskeleton that were previously thought to be absent in SEs. Our results are in contradiction to this old dogma of plant physiology and the potential of mature sieve elements should therefore be re-evaluated. In addition, SUT1 internalization was found to be dependent on the plasma membrane lipid composition. SUT1 belongs to the detergent-resistant membrane （DRM） fraction in planta and is targeted to membrane raft-like microdomains when expressed in yeast （Kr（igel et al,, 2008）, Here, SUT1-GFP expression in different yeast mutants, which were unable to perform en- docytosis and/or raft formation, revealed a strong link between SUT1 raft localization, the sterol composition and mem- brane potential of the yeast plasma membrane, and the capacity of the SUT1 protein to be internalized by endocytosis. The results provide new insight into the regulation of sucrose transport and the mechanism of endocytosis in plant cells.
文摘In the phloem cap region o i Arabidopsis plants,sulfur-rich cells(S-cells)accumulate>100 mM glucosinolates(GLS),but are biosynthetically inactive.The source and route of S-cell-bound GLS remain elusive.In this study,using single-cell sampling and scanning electron microscopy with energy-dispersive X-ray analysis we show that two GLS importers,NPF2.10/GTR1 and NPF2.11/GTR2,are critical for GLS accumulation in S-cells,although they are not localized in the S-cells.Comparison of GLS levels in S-cells in multiple combinations of homo-and heterografts o lg t r l gtr2,biosynthetic null mutant and wild-type plants indicate that S-cells accumulate GLS via symplasmic connections either directly from neighboring biosynthetic cells or indirectly to non-neighboring cells expressing GTR1/2.Distinct sources and transport routes exist for different types of GLS,and vary depending on the position of S-cells in the inflorescence stem.Based on these findings,we propose a model illustrating the GLS transport routes either directly from biosynthetic cells or via GTR-mediated import from apoplastic space radially into a symplasmic domain,wherein the S-cells are the ultimate sink.Similarly,we observed accumulation of the cyanogenic glucoside defensive compounds in high-turgor cells in the phloem cap of Lotus japonicus,suggesting that storage of defensive compounds in high-turgor cells may be a general mechanism for chemical protection of the phloem cap.
文摘Background:Acute-onset neurodegenerative diseases in older patients are rare clinical cases,especially when the degeneration only affects specific regions of the nervous system.Several neurological disorders have been described in which the degeneration of brain parenchyma originates from and/or primarily affects the brain stem.Clinical diagnosis in these patients,however,is often complicated due to a poor understanding of these diseases and their underlying mechanisms.Case presentation:In this manuscript we report on a 73-year-old female who had experienced a sudden onset of complex neurological symptoms that progressively worsened over a period of 2 years.Original evaluation had suggested a MRI-negative stroke as underlying pathogenesis.The combination of patient’s medical history,clinical examination and exceptional pattern of brain stem degeneration presenting as“kissing swan sign”in MR imaging was strongly suggestive of acute onset of Alexander’s disease.This leukoencephalopathy is caused by GFAP(glial fibrilary acidic protein)gene mutations and may present with brain stem atrophy and stroke-like onset of symptoms in elderly individuals.However,a pathognomonic GFAP gene mutation could not be identified by Sanger sequencing.Conclusions:After an extended differential diagnosis and exclusion of other diseases,a definite diagnosis of the patient’s condition presently remains elusive.However,whole-exome sequencing performed from patient’s blood revealed 12 potentially disease-causative heterozygous variants,amongst which several have been associated with neurological disorders in vitro and in vivo–in particular the axon degeneration-related NMNAT2 gene.
