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Chen F, Rao M, Ye J, Luan S, Shepard D, Cao D. MO-D-BRB-01: Study of Systemic and Random Errors On VMAT and IMRT Plan Quality and Deliver Accuracy. Med Phys 2009. [DOI: 10.1118/1.3182211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Fahimian B, DeMarco J, Keyes R, Luan S, Zankl M, Holzscheiter M. WE-C-BRB-06: Antiproton Radiotherapy: Development of Physically and Biologically Optimized Monte Carlo Treatment Planning Systems for Intensity and Energy Modulated Delivery. Med Phys 2009. [DOI: 10.1118/1.3182464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Luan S, Swanson N, Chen Z, Ma L. SU-EE-A2-05: A Planning System for Dynamic Gamma Knife Radiosurgery. Med Phys 2009. [DOI: 10.1118/1.3181103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Luan S, Wang C, Tang G, Chen D, Yu C. SU-GG-T-96: IMRT Leaf Sequencing with Intensity-Based Segment Weight Optimization. Med Phys 2008. [DOI: 10.1118/1.2961848] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Wang C, Luan S, Tang G, Chen D, Earl M, Yu C. SU-GG-T-542: Arc-Modulated Radiation Therapy (AMRT): A Novel Method for Rotational Radiation Therapy. Med Phys 2008. [DOI: 10.1118/1.2962291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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31
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Tang G, Earl M, Luan S, Wang C, Naqvi S, Yu C. TU-EE-A1-06: Comparison of Intensity-Modulated Radiation Therapy, Intensity-Modulated Arc Therapy and Arc-Modulated Radiation Therapy. Med Phys 2008. [DOI: 10.1118/1.2962610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Tang G, Earl M, Luan S, Wang C, Naqvi S, Yu C. TH-C-350-02: Is Dose Rate Variation Crucial for Single-Arc Radiation Therapy Delivery? Med Phys 2008. [DOI: 10.1118/1.2962827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Wang C, Luan S, Tang G, Chen D, Yu C. SU-GG-T-92: Dynamic Leaf Sequencing with Monitor Units Control. Med Phys 2008. [DOI: 10.1118/1.2961844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Tang G, Earl M, Luan S, Naqvi S, Yu C. Converting Multiple-Arc Intensity Modulated Arc Therapy Into a Single Arc for Efficient Delivery. Int J Radiat Oncol Biol Phys 2007. [DOI: 10.1016/j.ijrobp.2007.07.2031] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Luan S, Wang C, Cao D, Chen D, Shepard D, Yu C. TH-C-AUD-01: IMAT Leaf Sequencing Using Graph Algorithms. Med Phys 2007. [DOI: 10.1118/1.2761660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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36
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Swanson N, Luan S, Li K, Ma L. TH-D-AUD-01: A Dynamic Dose Delivery Model for Gamma Knife Radiosurgery. Med Phys 2007. [DOI: 10.1118/1.2761720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Luan S, Wang C, Cao D, Chen D, D'Souza W, Yu C. SU-FF-J-102: Patient Breathing Motion Synchronized IMAT: A New Technique for Compensating Intra-Fraction Organ Motions. Med Phys 2006. [DOI: 10.1118/1.2240878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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38
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Cao D, Earl M, Luan S, Shepard D. TU-D-ValA-03: Continuous Intensity Map Optimization (CIMO): A Novel Leaf-Sequencing Algorithm. Med Phys 2006. [DOI: 10.1118/1.2241572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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39
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Luan S, Heintz P, Sorensen S, Jimenez A, Roedersheimer K, Chen D, Wong G. The Effect of Collimator Rotation on IMRT Treatment Planning. Int J Radiat Oncol Biol Phys 2005. [DOI: 10.1016/j.ijrobp.2005.07.886] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Roedersheimer K, Chen DZ, Luan S, Xing L. SU-FF-T-105: The Impact of Multileaf Collimator Rotation in IMRT Planning. Med Phys 2005. [DOI: 10.1118/1.1997776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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41
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Wang C, Luan S, Chen DZ, Hu X, Yu C. SU-FF-T-97: A Generalized MLC Segmentation Algorithm for Step-And-Shoot IMRT with No Tongue-And-Groove Error. Med Phys 2005. [DOI: 10.1118/1.1997768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Abstract
A number of environmental conditions including drought, low humidity, cold and salinity subject plants to osmotic stress. A rapid plant response to such stress conditions is stomatal closure to reduce water loss from plants. From an external stress signal to stomatal closure, many molecular components constitute a signal transduction network that couples the stimulus to the response. Numerous studies have been directed to resolving the framework and molecular details of stress signalling pathways in plants. In guard cells, studies focus on the regulation of ion channels by abscisic acid (ABA), a chemical messenger for osmotic stress. Calcium, protein kinases and phosphatases, and membrane trafficking components have been shown to play a role in ABA signalling process in guard cells. Studies also implicate ABA-independent regulation of ion channels by osmotic stress. In particular, a direct osmosensing pathway for ion channel regulation in guard cells has been identified. These pathways form a complex signalling web that monitors water status in the environment and initiates responses in stomatal movements.
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Li L, Tutone AF, Drummond RS, Gardner RC, Luan S. A novel family of magnesium transport genes in Arabidopsis. THE PLANT CELL 2001; 13:2761-75. [PMID: 11752386 PMCID: PMC139487 DOI: 10.1105/tpc.010352] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2001] [Accepted: 09/04/2001] [Indexed: 05/18/2023]
Abstract
Magnesium (Mg(2+)) is the most abundant divalent cation in plant cells and plays a critical role in many physiological processes. We describe the identification of a 10-member Arabidopsis gene family (AtMGT) encoding putative Mg(2+) transport proteins. Most members of the AtMGT family are expressed in a range of Arabidopsis tissues. One member of this family, AtMGT1, functionally complemented a bacterial mutant lacking Mg(2+) transport capability. A second member, AtMGT10, complemented a yeast mutant defective in Mg(2+) uptake and increased the cellular Mg(2+) content of starved cells threefold during a 60-min uptake period. (63)Ni tracer studies in bacteria showed that AtMGT1 has highest affinity for Mg(2+) but may also be capable of transporting several other divalent cations, including Ni(2+), Co(2+), Fe(2+), Mn(2+), and Cu(2+). However, the concentrations required for transport of these other cations are beyond normal physiological ranges. Both AtMGT1 and AtMGT10 are highly sensitive to Al(3+) inhibition, providing potential molecular targets for Al(3+) toxicity in plants. Using green fluorescence protein as a reporter, we localized AtMGT1 protein to the plasma membrane in Arabidopsis plants. We suggest that the AtMGT gene family encodes a Mg(2+) transport system in higher plants.
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Li L, Tutone AF, Drummond RS, Gardner RC, Luan S. A novel family of magnesium transport genes in Arabidopsis. THE PLANT CELL 2001. [PMID: 11752386 DOI: 10.1105/tpc.13.12.2761] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Magnesium (Mg(2+)) is the most abundant divalent cation in plant cells and plays a critical role in many physiological processes. We describe the identification of a 10-member Arabidopsis gene family (AtMGT) encoding putative Mg(2+) transport proteins. Most members of the AtMGT family are expressed in a range of Arabidopsis tissues. One member of this family, AtMGT1, functionally complemented a bacterial mutant lacking Mg(2+) transport capability. A second member, AtMGT10, complemented a yeast mutant defective in Mg(2+) uptake and increased the cellular Mg(2+) content of starved cells threefold during a 60-min uptake period. (63)Ni tracer studies in bacteria showed that AtMGT1 has highest affinity for Mg(2+) but may also be capable of transporting several other divalent cations, including Ni(2+), Co(2+), Fe(2+), Mn(2+), and Cu(2+). However, the concentrations required for transport of these other cations are beyond normal physiological ranges. Both AtMGT1 and AtMGT10 are highly sensitive to Al(3+) inhibition, providing potential molecular targets for Al(3+) toxicity in plants. Using green fluorescence protein as a reporter, we localized AtMGT1 protein to the plasma membrane in Arabidopsis plants. We suggest that the AtMGT gene family encodes a Mg(2+) transport system in higher plants.
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Luan S, Kudla J, Harter K, Gruissem W, Chory J. Renaming genes and duplication of gene names in the literature. THE PLANT CELL 2001; 13:2391-2392. [PMID: 11701876 PMCID: PMC2652722 DOI: 10.1105/tpc.131140] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Liu K, Luan S. Internal aluminum block of plant inward K(+) channels. THE PLANT CELL 2001; 13:1453-65. [PMID: 11402172 PMCID: PMC135577 DOI: 10.1105/tpc.13.6.1453] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2001] [Accepted: 03/29/2001] [Indexed: 05/23/2023]
Abstract
Aluminum (Al) inhibits inward K(+) channels (K(in)) in both root hair and guard cells, which accounts for at least part of the Al toxicity in plants. To understand the mechanism of Al-induced K(in) inhibition, we performed patch clamp analyses on K(in) in guard cells and on KAT1 channels expressed in Xenopus oocytes. Our results show that Al inhibits plant K(in) by blocking the channels at the cytoplasmic side of the plasma membrane. In guard cells, single-channel recording revealed that Al inhibition of K(in) occurred only upon internal exposure. Using both "giant patch" recording and single-channel analyses, we found that Al reduced KAT1 open probability and changed its activation kinetics through an internal membrane-delimited mechanism. We also provide evidence that a Ca(2)+ channel-like pathway that is sensitive to antagonists verapamil and La(3)+ mediates Al entry across the plasma membrane. We conclude that Al enters plant cells through a Ca(2)+ channel-like pathway and inhibits K(+) uptake by internally blocking K(in).
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Kim KN, Cheong YH, Gupta R, Luan S. Interaction specificity of Arabidopsis calcineurin B-like calcium sensors and their target kinases. PLANT PHYSIOLOGY 2000; 124:1844-53. [PMID: 11115898 PMCID: PMC59879 DOI: 10.1104/pp.124.4.1844] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2000] [Revised: 09/11/2000] [Accepted: 09/28/2000] [Indexed: 05/17/2023]
Abstract
Calcium is a critical component in a number of plant signal transduction pathways. A new family of calcium sensors called calcineurin B-like proteins (AtCBLs) have been recently identified from Arabidopsis. These calcium sensors have been shown to interact with a family of protein kinases (CIPKs). Here we report that each individual member of AtCBL family specifically interacts with a subset of CIPKs and present structural basis for the interaction and for the specificity underlying these interactions. Although the C-terminal region of CIPKs is responsible for interaction with AtCBLs, the N-terminal region of CIPKs is also involved in determining the specificity of such interaction. We have also shown that all three EF-hand motifs in AtCBL members are required for the interaction with CIPKs. Several AtCBL members failed to interact with any of the CIPKs presented in this study, suggesting that these AtCBL members either have other CIPKs as targets or they target distinct proteins other than CIPKs. These results may provide structural basis for the functional specificity of CBL family of calcium sensors and their targets.
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Liu K, Fu H, Bei Q, Luan S. Inward potassium channel in guard cells as a target for polyamine regulation of stomatal movements. PLANT PHYSIOLOGY 2000; 124:1315-26. [PMID: 11080307 PMCID: PMC59229 DOI: 10.1104/pp.124.3.1315] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2000] [Accepted: 08/03/2000] [Indexed: 05/18/2023]
Abstract
A number of studies show that environmental stress conditions such as drought, high salt, and air pollutants increase polyamine levels in plant cells. However, little is understood about the physiological function of elevated polyamine levels. We report here that polyamines regulate the voltage-dependent inward K(+) channel in the plasma membrane of guard cells and modulate stomatal aperture, a plant "sensor" to environmental changes. All natural polyamines, including spermidine, spermine, cadaverine, and putrescine, strongly inhibited opening and induced closure of stomata. Whole-cell patch-clamp analysis showed that intracellular application of polyamines inhibited the inward K(+) current across the plasma membrane of guard cells. Single-channel recording analysis indicated that polyamine regulation of the K(+) channel requires unknown cytoplasmic factors. In an effort to identify the target channel at the molecular level, we found that spermidine inhibited the inward K(+) current carried by KAT1 channel that was functionally expressed in a plant cell model. These findings suggest that polyamines target KAT1-like inward K(+) channels in guard cells and modulate stomatal movements, providing a link between stress conditions, polyamine levels, and stomatal regulation.
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Huang Y, Li H, Gupta R, Morris PC, Luan S, Kieber JJ. ATMPK4, an Arabidopsis homolog of mitogen-activated protein kinase, is activated in vitro by AtMEK1 through threonine phosphorylation. PLANT PHYSIOLOGY 2000; 122:1301-10. [PMID: 10759527 PMCID: PMC58966 DOI: 10.1104/pp.122.4.1301] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/1999] [Accepted: 11/23/1999] [Indexed: 05/18/2023]
Abstract
The modulation of mitogen-activated protein kinase (MAPK) activity regulates many intracellular signaling processes. In animal and yeast cells, MAP kinases are activated via phosphorylation by the dual-specificity kinase MEK (MAP kinase kinase). Several plant homologs of MEK and MAPK have been identified, but the biochemical events underlying the activation of plant MAPKs remain unknown. We describe the in vitro activation of an Arabidopsis homolog of MAP kinase, ATMPK4. ATMPK4 was phosphorylated in vitro by an Arabidopsis MEK homolog, AtMEK1. This phosphorylation occurred principally on threonine (Thr) residues and resulted in elevated ATMPK4 kinase activity. A second Arabidopsis MEK isoform, ATMAP2Kalpha, failed to phosphorylate ATMPK4 in vitro. Tyr dephosphorylation by the Arabidopsis Tyr-specific phosphatase AtPTP1 resulted in an almost complete loss of ATMPK4 activity. Immunoprecipitates of Arabidopsis extracts with anti-ATMPK4 antibodies displayed myelin basic protein kinase activity that was sensitive to treatment with AtPTP1. These results demonstrate that a plant MEK can phosphorylate and activate MAPK, and that Tyr phosphorylation is critical for the catalytic activity of MAPK in plants. Surprisingly, in contrast to the animal enzymes, AtMEK1 may not be a dual-specificity kinase but, rather, the required Tyr phosphorylation on ATMPK4 may result from autophosphorylation.
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Shi J, Kim KN, Ritz O, Albrecht V, Gupta R, Harter K, Luan S, Kudla J. Novel protein kinases associated with calcineurin B-like calcium sensors in Arabidopsis. THE PLANT CELL 1999; 11:2393-405. [PMID: 10590166 PMCID: PMC144142 DOI: 10.1105/tpc.11.12.2393] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Members of the Arabidopsis calcineurin B-like Ca(2)+ binding protein (AtCBL) family are differentially regulated by stress conditions. One AtCBL plays a role in salt stress; another is implicated in response to other stress signals, including drought, cold, and wounding. In this study, we identified a group of novel protein kinases specifically associated with AtCBL-type Ca(2)+ sensors. In addition to a typical protein kinase domain, they all contain a unique C-terminal region that is both required and sufficient for interaction with the AtCBL-type but not calmodulin-type Ca(2)+ binding proteins from plants. Interactions between the kinases and AtCBLs require micromolar concentrations of Ca(2)+, suggesting that increases in cellular Ca(2)+ concentrations may trigger the formation of AtCBL-kinase complexes in vivo. Unlike most serine/threonine kinases, the AtCBL-interacting kinase efficiently uses Mn(2)+ to Mg(2)+ as a cofactor and may function as a Mn(2)+ binding protein in the cell. These findings link a new type of Ca(2)+ sensors to a group of novel protein kinases, providing the molecular basis for a unique Ca(2)+ signaling machinery in plant cells.
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