Gravitropic curvature growth of Arabidopsis hypocotyls mainly occurred in the rapid growing Elongation Zone(EZI),not in the slow-growing Elongation Zone(EZII).By examining reorientation of Microtubules(MT)and phenotyp...Gravitropic curvature growth of Arabidopsis hypocotyls mainly occurred in the rapid growing Elongation Zone(EZI),not in the slow-growing Elongation Zone(EZII).By examining reorientation of Microtubules(MT)and phenotype of the cell wall in the EZI and the EZII of Arabidopsis hypocotyls under normal gravitational condition,it is found that MTs in the rapid growing epidermal cells were mainly in the transverse direction,while those in the non-growing epidermal cells were in the longitudinal directions.However,this difference in cortical MT arrays between the EZI and EZII cells disappeared when the seedlings were exposed to the simulated microgravity condition on a horizontal clinostat.Field emission scanning electron microscopy revealed that the surface texture of epidermal cells,like the direction of the MT,in the EZI and the EZII also became similar when exposed to the simulated microgravity condition.This result indicated that simulate microgravity could modify the potential differentiation between the EZI and the EZII by affecting the orientation of cortical MT in the epidermal cells.展开更多
Microtubules play a central role in cytoskeletal changes during neuronal development and maintenance.Microtubule dynamics is essential to polarity and shape transitions underlying neural cell division,differentiation,...Microtubules play a central role in cytoskeletal changes during neuronal development and maintenance.Microtubule dynamics is essential to polarity and shape transitions underlying neural cell division,differentiation,motility,and maturation.Kinesin superfamily protein 2A is a member of human kinesin 13 gene family of proteins that depolymerize and destabilize microtubules.In dividing cells,kinesin superfamily protein 2A is involved in mitotic progression,spindle assembly,and chromosome segregation.In postmitotic neurons,it is required for axon/dendrite specification and extension,neuronal migration,connectivity,and survival.Humans with kinesin superfamily protein 2A mutations suffer from a variety of malformations of cortical development,epilepsy,autism spectrum disorder,and neurodegeneration.In this review,we discuss how kinesin superfamily protein 2A regulates neuronal development and function,and how its deregulation causes neurodevelopmental and neurological disorders.展开更多
It has been known that the transverse orientation of cortical microtubules （MTs） along the elongation axis is essential for normal cell morphogenesis, but whether cortical MTs are essential for normal cell wall synt...It has been known that the transverse orientation of cortical microtubules （MTs） along the elongation axis is essential for normal cell morphogenesis, but whether cortical MTs are essential for normal cell wall synthesis is still not clear. In the present study, we have investigated whether cortical MTs affect cell wall synthesis by direct alteration of the cortical MT organization in Arabidopsis thaliana. Disruption of the cortical MT organization by expression of an excess amount of green fluorescent protein-tagged a-tubulin 6 （GFP-TUA6） in transgenic Arabidopsis plants was found to cause a marked reduction in cell wall thickness and a de- crease in the cell wall sugars glucose and xylose. Concomitantly, the stem strength of the GFP-TUA6 overexpressors was markedly reduced compared with the wild type. In addition, expression of excess GFP- TUA6 results in an alteration in cell morphogenesis and a severe effect on plant growth and development. Together, these results suggest that the proper organization of cortical MTs is essential for the normal synthesis of plant cell walls.展开更多
Plant interphase cortical microtubules(cMTs)mediate anisotropic cell expansion in response to environmental and developmental cues.In Arabidopsis thaliana,KATANIN 1(KTN1),the p60 catalytic subunit of the conserved MT-...Plant interphase cortical microtubules(cMTs)mediate anisotropic cell expansion in response to environmental and developmental cues.In Arabidopsis thaliana,KATANIN 1(KTN1),the p60 catalytic subunit of the conserved MT-severing enzyme katanin,is essential for cMT ordering and anisotropic cell expansion.However,the regulation of KTN1-mediated cMT severing and ordering remains unclear.In this work,we report that the Arabidopsis IQ67 DOMAIN(IQD)family gene ABNORMAL SHOOT 6(ABS6)encodes a MT-associated protein.Overexpression of ABS6 leads to elongated cotyledons,directional pavement cell expansion,and highly ordered transverse cMT arrays.Genetic suppressor analysis revealed that ABS6-mediated cMT ordering is dependent on KTN1 and SHADE AVOIDANCE 4(SAV4).Live imaging of cMT dynamics showed that both ABS6 and SAV4 function as positive regulators of cMT severing.Furthermore,ABS6 directly interacts with KTN1 and SAV4 and promotes their recruitment to the cMTs.Finally,analysis of loss-of-function mutant combinations showed that ABS6,SAV4,and KTN1 work together to ensure the robust ethylene response in the apical hook of dark-grown seedlings.Together,our findings establish ABS6 and SAV4 as positive regulators of cMT severing and ordering,and highlight the role of cMT dynamics in fine-tuning differential growth in plants.展开更多
Cell division and expansion require the ordered arrangement of microtubules, which are subject to spatial and temporal modifications by developmental and environmental factors. Understanding how signals translate to c...Cell division and expansion require the ordered arrangement of microtubules, which are subject to spatial and temporal modifications by developmental and environmental factors. Understanding how signals translate to changes in cortical microtubule organization is of fundamental importance. A defining feature of the cortical microtubule array is its association with the plasma membrane; modules of the plasma membrane are thought to play important roles in the mediation of microtubule organization. In this review, we highlight advances in research on the regulation of cortical microtubule organization by membrane-associated and membrane-tethered proteins and lipids in response to phytohormones and stress. The transmembrane kinase receptor Rho-like guanosine triphosphatase, phospholipase D, phosphatidic acid, and phosphoinositides are discussed with a focus on their roles in microtubule organization.展开更多
A microtubule nucleates from a γ-tubuUn complex, which consists of γ-tubulin, proteins from the SPC971SPC98 family, and the WD40 motif protein GCP-WD. We analyzed the phylogenetic relationships of the genes encoding...A microtubule nucleates from a γ-tubuUn complex, which consists of γ-tubulin, proteins from the SPC971SPC98 family, and the WD40 motif protein GCP-WD. We analyzed the phylogenetic relationships of the genes encoding these proteins and found that the components of this complex are widely conserved among land plants and other eukaryotes. By contrast, the interphase and mitotic arrays of microtubules in land plants differ from those in other eukaryotes. In the interphase cortical array, the majority of microtubules nucleate on existing microtubules in the absence of conspicuous microtubule organizing centers （MTOCs）, such as a centrosome. During mitosis, the spindle also forms in the absence of conspicuous MTOCs. Both poles of the spindle are broad, and branched structures of microtubules called microtubule converging centers form at the poles. In this review, we hypothesize that the microtubule converging centers form via microtubule-dependent microtubule nucleation, as in the case of the interphase arrays. The evolutionary insights arising from the molecular basis of the diversity in microtubule organization are discussed.展开更多
The organization of the microtubule cytoskeleton is critical for cell and organ morphogenesis.The evolutionarily conserved microtubule-severing enzyme KATANIN plays critical roles in microtubule organization in the pl...The organization of the microtubule cytoskeleton is critical for cell and organ morphogenesis.The evolutionarily conserved microtubule-severing enzyme KATANIN plays critical roles in microtubule organization in the plant and animal kingdoms.We previously used conical cell of Arabidopsis thaliana petals as a model system to investigate cortical microtubule organization and cell morphogenesis and determined that KATANIN promotes the formation of circumferential cortical microtubule arrays in conical cells.Here,we demonstrate that the conserved protein phosphatase PP2A interacts with and dephosphorylates KATANIN to promote the formation of circumferential cortical microtubule arrays in conical cells.KATANIN undergoes cycles of phosphorylation and dephosphorylation.Using co-immunoprecipitation coupled with mass spectrometry,we identified PP2A subunits as KATANIN-interacting proteins.Further biochemical studies showed that PP2 A interacts with and dephosphorylates KATANIN to stabilize its cellular abundance.Similar to the katanin mutant,mutants for genes encoding PP2A subunits showed disordered cortical microtubule arrays and defective conical cell shape.Taken together,these findings identify PP2A as a regulator of conical cell shape and suggest that PP2A mediates KATANIN phospho-regulation during plant cell morphogenesis.展开更多
The Arabidopsis FRA1 kinesin contributes to the organization of cellulose microfibrils through an unknown mechanism. The cortical localization of this kinesin during interphase raises the possibility that it transport...The Arabidopsis FRA1 kinesin contributes to the organization of cellulose microfibrils through an unknown mechanism. The cortical localization of this kinesin during interphase raises the possibility that it transports cell wallrelated cargoes along cortical microtubules that either directly or indirectly influence cellulose microfibril patterning. To determine whether FRA1 is an authentic motor protein, we combined bulk biochemical assays and single molecule fluorescence imaging to analyze the motor properties of recombinant, GFP-tagged FRA1 containing the motor and coiled-coil domains （designated as FRAI（707）-GFP）. We found that FRAI（707）-GFP binds to microtubules in an ATP-dependent manner and that its ATPase activity is dramatically stimulated by the presence of microtubules. Using single molecule studies, we found that FRAI（707）-GFP moves processively along microtubule tracks at a velocity of about 0.4 μm s-1. In addition, we found that FRAI（707）-GFP is a microtubule plus-end-directed motor and that it moves along microtubules as a dimer. Interestingly, our single molecule analysis shows that the processivity of FRAI（707）-GFP is at least twice the processivity of conventional kinesin, making FRA1 the most processive kinesin to date. Together, our data show that FRA1 is a bona fide motor protein that has the potential to drive Iong-distance transport of cargo along cortical microtubules.展开更多
基金Supported by the China Manned Space Flight Technology Project TG-2the National Natural Science Foundation of China(31670864)+2 种基金the National Natural Fund Joint Fund Project(U1738106)the Strategic Pioneer Projects of CAS(XDA15013900)the National Science Foundation for Young Scientists of China(31500687)
文摘Gravitropic curvature growth of Arabidopsis hypocotyls mainly occurred in the rapid growing Elongation Zone(EZI),not in the slow-growing Elongation Zone(EZII).By examining reorientation of Microtubules(MT)and phenotype of the cell wall in the EZI and the EZII of Arabidopsis hypocotyls under normal gravitational condition,it is found that MTs in the rapid growing epidermal cells were mainly in the transverse direction,while those in the non-growing epidermal cells were in the longitudinal directions.However,this difference in cortical MT arrays between the EZI and EZII cells disappeared when the seedlings were exposed to the simulated microgravity condition on a horizontal clinostat.Field emission scanning electron microscopy revealed that the surface texture of epidermal cells,like the direction of the MT,in the EZI and the EZII also became similar when exposed to the simulated microgravity condition.This result indicated that simulate microgravity could modify the potential differentiation between the EZI and the EZII by affecting the orientation of cortical MT in the epidermal cells.
基金Fund for Scientific Research(FNRS)PDR T0236.20FNRS-Exellence of Science 30913351FNRS CDR J.0175.23(to FT)。
文摘Microtubules play a central role in cytoskeletal changes during neuronal development and maintenance.Microtubule dynamics is essential to polarity and shape transitions underlying neural cell division,differentiation,motility,and maturation.Kinesin superfamily protein 2A is a member of human kinesin 13 gene family of proteins that depolymerize and destabilize microtubules.In dividing cells,kinesin superfamily protein 2A is involved in mitotic progression,spindle assembly,and chromosome segregation.In postmitotic neurons,it is required for axon/dendrite specification and extension,neuronal migration,connectivity,and survival.Humans with kinesin superfamily protein 2A mutations suffer from a variety of malformations of cortical development,epilepsy,autism spectrum disorder,and neurodegeneration.In this review,we discuss how kinesin superfamily protein 2A regulates neuronal development and function,and how its deregulation causes neurodevelopmental and neurological disorders.
文摘It has been known that the transverse orientation of cortical microtubules （MTs） along the elongation axis is essential for normal cell morphogenesis, but whether cortical MTs are essential for normal cell wall synthesis is still not clear. In the present study, we have investigated whether cortical MTs affect cell wall synthesis by direct alteration of the cortical MT organization in Arabidopsis thaliana. Disruption of the cortical MT organization by expression of an excess amount of green fluorescent protein-tagged a-tubulin 6 （GFP-TUA6） in transgenic Arabidopsis plants was found to cause a marked reduction in cell wall thickness and a de- crease in the cell wall sugars glucose and xylose. Concomitantly, the stem strength of the GFP-TUA6 overexpressors was markedly reduced compared with the wild type. In addition, expression of excess GFP- TUA6 results in an alteration in cell morphogenesis and a severe effect on plant growth and development. Together, these results suggest that the proper organization of cortical MTs is essential for the normal synthesis of plant cell walls.
基金the Teaching and Research Core Facility at the College of Life Sciences,NWAFU for support in this worksupported by grants from the National Natural Science Foundation of China(31770205 and 31970186 to X.L.,31870268 to F.Y.)。
文摘Plant interphase cortical microtubules(cMTs)mediate anisotropic cell expansion in response to environmental and developmental cues.In Arabidopsis thaliana,KATANIN 1(KTN1),the p60 catalytic subunit of the conserved MT-severing enzyme katanin,is essential for cMT ordering and anisotropic cell expansion.However,the regulation of KTN1-mediated cMT severing and ordering remains unclear.In this work,we report that the Arabidopsis IQ67 DOMAIN(IQD)family gene ABNORMAL SHOOT 6(ABS6)encodes a MT-associated protein.Overexpression of ABS6 leads to elongated cotyledons,directional pavement cell expansion,and highly ordered transverse cMT arrays.Genetic suppressor analysis revealed that ABS6-mediated cMT ordering is dependent on KTN1 and SHADE AVOIDANCE 4(SAV4).Live imaging of cMT dynamics showed that both ABS6 and SAV4 function as positive regulators of cMT severing.Furthermore,ABS6 directly interacts with KTN1 and SAV4 and promotes their recruitment to the cMTs.Finally,analysis of loss-of-function mutant combinations showed that ABS6,SAV4,and KTN1 work together to ensure the robust ethylene response in the apical hook of dark-grown seedlings.Together,our findings establish ABS6 and SAV4 as positive regulators of cMT severing and ordering,and highlight the role of cMT dynamics in fine-tuning differential growth in plants.
基金This work was supported by grants from the National Basic Research Program （973 Program） （No. 2012CB114200）, the National Natural Science Foundation of China （Grant No. 91117003）, the Fundamental Research Funds for the Central Universities （KYT7201402）, and RAPD project to W Zhang, and grants from the National Natural Science Foundation of China （Grant No. 31470364） and the Fundamental Research Funds for the Central Universities （KYZ201423） to Q Zhang.
文摘Cell division and expansion require the ordered arrangement of microtubules, which are subject to spatial and temporal modifications by developmental and environmental factors. Understanding how signals translate to changes in cortical microtubule organization is of fundamental importance. A defining feature of the cortical microtubule array is its association with the plasma membrane; modules of the plasma membrane are thought to play important roles in the mediation of microtubule organization. In this review, we highlight advances in research on the regulation of cortical microtubule organization by membrane-associated and membrane-tethered proteins and lipids in response to phytohormones and stress. The transmembrane kinase receptor Rho-like guanosine triphosphatase, phospholipase D, phosphatidic acid, and phosphoinositides are discussed with a focus on their roles in microtubule organization.
文摘A microtubule nucleates from a γ-tubuUn complex, which consists of γ-tubulin, proteins from the SPC971SPC98 family, and the WD40 motif protein GCP-WD. We analyzed the phylogenetic relationships of the genes encoding these proteins and found that the components of this complex are widely conserved among land plants and other eukaryotes. By contrast, the interphase and mitotic arrays of microtubules in land plants differ from those in other eukaryotes. In the interphase cortical array, the majority of microtubules nucleate on existing microtubules in the absence of conspicuous microtubule organizing centers （MTOCs）, such as a centrosome. During mitosis, the spindle also forms in the absence of conspicuous MTOCs. Both poles of the spindle are broad, and branched structures of microtubules called microtubule converging centers form at the poles. In this review, we hypothesize that the microtubule converging centers form via microtubule-dependent microtubule nucleation, as in the case of the interphase arrays. The evolutionary insights arising from the molecular basis of the diversity in microtubule organization are discussed.
基金financially supported by grants from the Natural Science Foundation of Fujian Province(2018J01600)the National Natural Science Foundation of China(31822003,31771344,and 31500160)。
文摘The organization of the microtubule cytoskeleton is critical for cell and organ morphogenesis.The evolutionarily conserved microtubule-severing enzyme KATANIN plays critical roles in microtubule organization in the plant and animal kingdoms.We previously used conical cell of Arabidopsis thaliana petals as a model system to investigate cortical microtubule organization and cell morphogenesis and determined that KATANIN promotes the formation of circumferential cortical microtubule arrays in conical cells.Here,we demonstrate that the conserved protein phosphatase PP2A interacts with and dephosphorylates KATANIN to promote the formation of circumferential cortical microtubule arrays in conical cells.KATANIN undergoes cycles of phosphorylation and dephosphorylation.Using co-immunoprecipitation coupled with mass spectrometry,we identified PP2A subunits as KATANIN-interacting proteins.Further biochemical studies showed that PP2 A interacts with and dephosphorylates KATANIN to stabilize its cellular abundance.Similar to the katanin mutant,mutants for genes encoding PP2A subunits showed disordered cortical microtubule arrays and defective conical cell shape.Taken together,these findings identify PP2A as a regulator of conical cell shape and suggest that PP2A mediates KATANIN phospho-regulation during plant cell morphogenesis.
文摘The Arabidopsis FRA1 kinesin contributes to the organization of cellulose microfibrils through an unknown mechanism. The cortical localization of this kinesin during interphase raises the possibility that it transports cell wallrelated cargoes along cortical microtubules that either directly or indirectly influence cellulose microfibril patterning. To determine whether FRA1 is an authentic motor protein, we combined bulk biochemical assays and single molecule fluorescence imaging to analyze the motor properties of recombinant, GFP-tagged FRA1 containing the motor and coiled-coil domains （designated as FRAI（707）-GFP）. We found that FRAI（707）-GFP binds to microtubules in an ATP-dependent manner and that its ATPase activity is dramatically stimulated by the presence of microtubules. Using single molecule studies, we found that FRAI（707）-GFP moves processively along microtubule tracks at a velocity of about 0.4 μm s-1. In addition, we found that FRAI（707）-GFP is a microtubule plus-end-directed motor and that it moves along microtubules as a dimer. Interestingly, our single molecule analysis shows that the processivity of FRAI（707）-GFP is at least twice the processivity of conventional kinesin, making FRA1 the most processive kinesin to date. Together, our data show that FRA1 is a bona fide motor protein that has the potential to drive Iong-distance transport of cargo along cortical microtubules.
