Sucrose is the principal product of photosynthesis used for the distribution of assimilated carbon in plants. Transport mechanisms and efficiency influence photosynthetic productivity by relieving product inhibition a...Sucrose is the principal product of photosynthesis used for the distribution of assimilated carbon in plants. Transport mechanisms and efficiency influence photosynthetic productivity by relieving product inhibition and contribute to plant vigor by controlling source/sink relationships and biomass partitioning. Sucrose is synthesized in the cytoplasm and may move cell to cell through plasmodesmata or may cross membranes to be compartmentalized or exported to the apoplasm for uptake into adjacent cells. As a relatively large polar compound, sucrose requires proteins to facilitate efficient membrane transport. Transport across the tonoplast by facilitated diffusion, antiport with protons, and symport with protons have been proposed; for transport across plasma membranes, symport with protons and a mechanism resembling facilitated diffusion are evident. Despite decades of research, only symport with protons is well established at the molecular level. This review aims to integrate recent and older studies on sucrose flux across membranes with principles of whole-plant carbon partitioning.展开更多
Ethylene insensitive 2 （EIN2）, an integral membrane protein of the ER network, has been identified as the central regulator of the ethylene signaling pathway. Still, the mechanism by which the ethylene signal is tra...Ethylene insensitive 2 （EIN2）, an integral membrane protein of the ER network, has been identified as the central regulator of the ethylene signaling pathway. Still, the mechanism by which the ethylene signal is transferred from the receptors to EIN2 has not been solved yet. Here, we show that protein phosphorylation is a key mechanism to control the interaction of EIN2 and the receptors. In vivo and in vitro fluorescence studies reveal that the kinase domain of the receptors is essential for the interaction. Cyanide, an ethylene agonist, which is known to reduce auto-phosphorylation of the ethylene receptor ethylene resistant 1 （ETR1） or a mutation in the kinase domain of ETR1 that prevents autophosphorylation （H353A）, increases the affinity of the receptors for EIN2. On the other hand, mimicking permanent auto-phosphorylation of ETR1 as in the mutant H353E releases the EiN2-ETR1 interaction from the control by the plant hormone. Based on our data, we propose a novel model on the integration of EIN2 in the ethylene signaling cascade.展开更多
目的研究经基因诊断确诊的遗传性压迫易感性神经病(hereditary neuropathy with liability to pressure palsies,HNPP)患者的临床特点和电生理特征。方法对来自4个家系的5例HNPP患者进行基因诊断,并总结患者的临床特点,同时分析其电生...目的研究经基因诊断确诊的遗传性压迫易感性神经病(hereditary neuropathy with liability to pressure palsies,HNPP)患者的临床特点和电生理特征。方法对来自4个家系的5例HNPP患者进行基因诊断,并总结患者的临床特点,同时分析其电生理特征,包括肌电图(EMG)、运动神经传导速度(MCV)和感觉神经传导速度(SCV)。结果5例患者均存在周围髓鞘蛋白22 (peripheral myelination protein 22,PMP22)基因缺失。HNPP临床主要表现为反复发作的肢体麻木、无力,神经传导存在广泛异常。结论电生理检查对HNPP的诊断很重要,基因检测发现PMP22基因缺失是诊断HNPP的金标准。展开更多
Plant viruses are a class of plant pathogens that specialize in movement from cell to cell. As part of their arsenal for infection of plants, every virus encodes a movement protein （MP）, a protein dedicated to enlar...Plant viruses are a class of plant pathogens that specialize in movement from cell to cell. As part of their arsenal for infection of plants, every virus encodes a movement protein （MP）, a protein dedicated to enlarging the pore size of plasmodesmata （PD） and actively transporting the viral nucleic acid into the adjacent cell. As our knowledge of intercellular transport has increased, it has become apparent that viruses must also use an active mechanism to target the virus from their site of replication within the cell to the PD. Just as viruses are too large to fit through an unmodified plasmodesma, they are also too large to be freely diffused through the cytoplasm of the cell. Evidence has accumulated now for the involvement of other categories of viral proteins in intracellular movement in addition to the MP, including viral proteins originally associated with replication or gene expression. In this review, we will discuss the strategies that viruses use for intracellular movement from the replication site to the PD, in particular focusing on the role of host membranes for intracellular transport and the coordinated interactions between virus proteins within cells that are necessary for successful virus spread.展开更多
文摘Sucrose is the principal product of photosynthesis used for the distribution of assimilated carbon in plants. Transport mechanisms and efficiency influence photosynthetic productivity by relieving product inhibition and contribute to plant vigor by controlling source/sink relationships and biomass partitioning. Sucrose is synthesized in the cytoplasm and may move cell to cell through plasmodesmata or may cross membranes to be compartmentalized or exported to the apoplasm for uptake into adjacent cells. As a relatively large polar compound, sucrose requires proteins to facilitate efficient membrane transport. Transport across the tonoplast by facilitated diffusion, antiport with protons, and symport with protons have been proposed; for transport across plasma membranes, symport with protons and a mechanism resembling facilitated diffusion are evident. Despite decades of research, only symport with protons is well established at the molecular level. This review aims to integrate recent and older studies on sucrose flux across membranes with principles of whole-plant carbon partitioning.
文摘Ethylene insensitive 2 （EIN2）, an integral membrane protein of the ER network, has been identified as the central regulator of the ethylene signaling pathway. Still, the mechanism by which the ethylene signal is transferred from the receptors to EIN2 has not been solved yet. Here, we show that protein phosphorylation is a key mechanism to control the interaction of EIN2 and the receptors. In vivo and in vitro fluorescence studies reveal that the kinase domain of the receptors is essential for the interaction. Cyanide, an ethylene agonist, which is known to reduce auto-phosphorylation of the ethylene receptor ethylene resistant 1 （ETR1） or a mutation in the kinase domain of ETR1 that prevents autophosphorylation （H353A）, increases the affinity of the receptors for EIN2. On the other hand, mimicking permanent auto-phosphorylation of ETR1 as in the mutant H353E releases the EiN2-ETR1 interaction from the control by the plant hormone. Based on our data, we propose a novel model on the integration of EIN2 in the ethylene signaling cascade.
文摘目的研究经基因诊断确诊的遗传性压迫易感性神经病(hereditary neuropathy with liability to pressure palsies,HNPP)患者的临床特点和电生理特征。方法对来自4个家系的5例HNPP患者进行基因诊断,并总结患者的临床特点,同时分析其电生理特征,包括肌电图(EMG)、运动神经传导速度(MCV)和感觉神经传导速度(SCV)。结果5例患者均存在周围髓鞘蛋白22 (peripheral myelination protein 22,PMP22)基因缺失。HNPP临床主要表现为反复发作的肢体麻木、无力,神经传导存在广泛异常。结论电生理检查对HNPP的诊断很重要,基因检测发现PMP22基因缺失是诊断HNPP的金标准。
文摘Plant viruses are a class of plant pathogens that specialize in movement from cell to cell. As part of their arsenal for infection of plants, every virus encodes a movement protein （MP）, a protein dedicated to enlarging the pore size of plasmodesmata （PD） and actively transporting the viral nucleic acid into the adjacent cell. As our knowledge of intercellular transport has increased, it has become apparent that viruses must also use an active mechanism to target the virus from their site of replication within the cell to the PD. Just as viruses are too large to fit through an unmodified plasmodesma, they are also too large to be freely diffused through the cytoplasm of the cell. Evidence has accumulated now for the involvement of other categories of viral proteins in intracellular movement in addition to the MP, including viral proteins originally associated with replication or gene expression. In this review, we will discuss the strategies that viruses use for intracellular movement from the replication site to the PD, in particular focusing on the role of host membranes for intracellular transport and the coordinated interactions between virus proteins within cells that are necessary for successful virus spread.
