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
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
Katanin is a heterodimeric microtubule （MT） severing protein that uses energy from ATP hydrolysis to generate internal breaks along MTs. Katanin p60, one of the two subunits, possesses ATPase and MT-binding/severing...Katanin is a heterodimeric microtubule （MT） severing protein that uses energy from ATP hydrolysis to generate internal breaks along MTs. Katanin p60, one of the two subunits, possesses ATPase and MT-binding/severing activities, and the p 80 subunit is responsible for targeting of katanin to certain subcellular locations. In animals, katanin plays an important role in the release of MTs from their nucleation sites in the centrosome. It is also involved in severing MTs into smaller fragments which can serve as templates for further polymerization to increase MT number during meiotic and mitotic spindle assembly. Katanin homologs are present in a wide variety of plant species. The Arabidopsis katanin homolog has been shown to possess ATP-dependent MT severing activity in vitro and exhibit a punctate localization pattern at the cell cortex and the perinuclear region. Disruption of katanin functions by genetic mutations causes a delay in the disappearance of the perinuclear MT array and results in an aberrant organization of cortical MTs in elongating cells. Consequently, katanin mutations lead to defects in cell elongation, cellulose microfibril deposition, and hormonal responses. Studies of katanin in plants provide new insights into our understanding of its roles in cellular functions.展开更多
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.
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Supported by a grant from the US Department of Energy,Bioscience Division(DE-FG02-03ER15 415).
文摘Katanin is a heterodimeric microtubule （MT） severing protein that uses energy from ATP hydrolysis to generate internal breaks along MTs. Katanin p60, one of the two subunits, possesses ATPase and MT-binding/severing activities, and the p 80 subunit is responsible for targeting of katanin to certain subcellular locations. In animals, katanin plays an important role in the release of MTs from their nucleation sites in the centrosome. It is also involved in severing MTs into smaller fragments which can serve as templates for further polymerization to increase MT number during meiotic and mitotic spindle assembly. Katanin homologs are present in a wide variety of plant species. The Arabidopsis katanin homolog has been shown to possess ATP-dependent MT severing activity in vitro and exhibit a punctate localization pattern at the cell cortex and the perinuclear region. Disruption of katanin functions by genetic mutations causes a delay in the disappearance of the perinuclear MT array and results in an aberrant organization of cortical MTs in elongating cells. Consequently, katanin mutations lead to defects in cell elongation, cellulose microfibril deposition, and hormonal responses. Studies of katanin in plants provide new insights into our understanding of its roles in cellular functions.
