@article{ma_shatil-cohen_ben-dor_wigoda_perera_im_diminshtein_yu_boss_moshelion_et al._2014, title={Do phosphoinositides regulate membrane water permeability of tobacco protoplasts by enhancing the aquaporin pathway?}, volume={241}, ISSN={0032-0935 1432-2048}, url={http://dx.doi.org/10.1007/s00425-014-2216-x}, DOI={10.1007/s00425-014-2216-x}, abstractNote={Enhancing the membrane content of PtdInsP 2 , the already-recognized protein-regulating lipid, increased the osmotic water permeability of tobacco protoplasts, apparently by increasing the abundance of active aquaporins in their membranes. While phosphoinositides are implicated in cell volume changes and are known to regulate some ion channels, their modulation of aquaporins activity has not yet been reported for any organism. To examine this, we compared the osmotic water permeability (P f) of protoplasts isolated from tobacco (Nicotiana tabacum) cultured cells (NT1) with different (genetically lowered or elevated relative to controls) levels of inositol trisphosphate (InsP3) and phosphatidyl inositol [4,5] bisphosphate (PtdInsP2). To achieve this, the cells were transformed with, respectively, the human InsP3 5-phosphatase ('Ptase cells') or human phosphatidylinositol (4) phosphate 5-kinase ('PIPK cells'). The mean P f of the PIPK cells was several-fold higher relative to that of controls and Ptase cells. Three results favor aquaporins over the membrane matrix as underlying this excessive P f: (1) transient expression of the maize aquaporin ZmPIP2;4 in the PIPK cells increased P f by 12-30 μm s(-1), while in the controls only by 3-4 μm s(-1). (2) Cytosol acidification-known to inhibit aquaporins-lowered the P f in the PIPK cells down to control levels. (3) The transcript of at least one aquaporin was elevated in the PIPK cells. Together, the three results demonstrate the differences between the PIPK cells and their controls, and suggest a hitherto unobserved regulation of aquaporins by phosphoinositides, which could occur through direct interaction or indirect phosphoinositides-dependent cellular effects.}, number={3}, journal={Planta}, publisher={Springer Science and Business Media LLC}, author={Ma, Xiaohong and Shatil-Cohen, Arava and Ben-Dor, Shifra and Wigoda, Noa and Perera, Imara Y. and Im, Yang Ju and Diminshtein, Sofia and Yu, Ling and Boss, Wendy F. and Moshelion, Menachem and et al.}, year={2014}, month={Dec}, pages={741–755} }
 @article{ischebeck_werner_krishnamoorthy_lerche_meijón_stenzel_löfke_wiessner_im_perera_et al._2013, title={Phosphatidylinositol 4,5-Bisphosphate Influences PIN Polarization by Controlling Clathrin-Mediated Membrane Trafficking in Arabidopsis}, volume={25}, ISSN={1040-4651 1532-298X}, url={http://dx.doi.org/10.1105/tpc.113.116582}, DOI={10.1105/tpc.113.116582}, abstractNote={AbstractThe functions of the minor phospholipid phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] during vegetative plant growth remain obscure. Here, we targeted two related phosphatidylinositol 4-phosphate 5-kinases (PI4P 5-kinases) PIP5K1 and PIP5K2, which are expressed ubiquitously in Arabidopsis thaliana. A pip5k1 pip5k2 double mutant with reduced PtdIns(4,5)P2 levels showed dwarf stature and phenotypes suggesting defects in auxin distribution. The roots of the pip5k1 pip5k2 double mutant had normal auxin levels but reduced auxin transport and altered distribution. Fluorescence-tagged auxin efflux carriers PIN-FORMED (PIN1)–green fluorescent protein (GFP) and PIN2-GFP displayed abnormal, partially apolar distribution. Furthermore, fewer brefeldin A–induced endosomal bodies decorated by PIN1-GFP or PIN2-GFP formed in pip5k1 pip5k2 mutants. Inducible overexpressor lines for PIP5K1 or PIP5K2 also exhibited phenotypes indicating misregulation of auxin-dependent processes, and immunolocalization showed reduced membrane association of PIN1 and PIN2. PIN cycling and polarization require clathrin-mediated endocytosis and labeled clathrin light chain also displayed altered localization patterns in the pip5k1 pip5k2 double mutant, consistent with a role for PtdIns(4,5)P2 in the regulation of clathrin-mediated endocytosis. Further biochemical tests on subcellular fractions enriched for clathrin-coated vesicles (CCVs) indicated that pip5k1 and pip5k2 mutants have reduced CCV-associated PI4P 5-kinase activity. Together, the data indicate an important role for PtdIns(4,5)P2 in the control of clathrin dynamics and in auxin distribution in Arabidopsis.}, number={12}, journal={The Plant Cell}, publisher={American Society of Plant Biologists (ASPB)}, author={Ischebeck, Till and Werner, Stephanie and Krishnamoorthy, Praveen and Lerche, Jennifer and Meijón, Mónica and Stenzel, Irene and Löfke, Christian and Wiessner, Theresa and Im, Yang Ju and Perera, Imara Y. and et al.}, year={2013}, month={Dec}, pages={4894–4911} }
 @article{boss_im_2012, title={Phosphoinositide Signaling}, volume={63}, ISSN={["1545-2123"]}, DOI={10.1146/annurev-arplant-042110-103840}, abstractNote={ All things flow and change…even in the stillest matter there is unseen flux and movement.  Attributed to Heraclitus (530–470 BC)  From The Story of Philosophy by Will Durant ( 28 )  Heraclitus, a Greek philosopher, was thinking on a much larger scale than molecular signaling; however, his visionary comments are an important reminder for those studying signaling today. Even in unstimulated cells, signaling pathways are in constant metabolic flux and provide basal signals that travel throughout the organism. In addition, negatively charged phospholipids, such as the polyphosphorylated inositol phospholipids, provide a circuit board of on/off switches for attracting or repelling proteins that define the membranes of the cell. This template of charged phospholipids is sensitive to discrete changes and metabolic fluxes—e.g., in pH and cations—which contribute to the oscillating signals in the cell. The inherent complexities of a constantly fluctuating system make understanding how plants integrate and process signals challenging. In this review we discuss one aspect of lipid signaling: the inositol family of negatively charged phospholipids and their functions as molecular sensors and regulators of metabolic flux in plants. }, journal={ANNUAL REVIEW OF PLANT BIOLOGY, VOL 63}, author={Boss, Wendy F. and Im, Yang Ju}, year={2012}, pages={409–429} }
 @article{boss_sederoff_im_moran_grunden_perera_2010, title={Basal Signaling Regulates Plant Growth and Development}, volume={154}, ISSN={["0032-0889"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77957739073&partnerID=MN8TOARS}, DOI={10.1104/pp.110.161232}, abstractNote={The term signal transduction refers to the classical paradigm where an external stimulus is sensed and initiates an increase in second messengers. Each second messenger transmits and amplifies the signal by activating a subset of downstream pathways. This complex network of interwoven downstream}, number={2}, journal={PLANT PHYSIOLOGY}, author={Boss, Wendy F. and Sederoff, Heike Winter and Im, Yang Ju and Moran, Nava and Grunden, Amy M. and Perera, Imara Y.}, year={2010}, month={Oct}, pages={439–443} }
 @article{im_ji_lee_killens_grunden_boss_2009, title={Expression of Pyrococcus furiosus Superoxide Reductase in Arabidopsis Enhances Heat Tolerance}, volume={151}, ISSN={["1532-2548"]}, DOI={10.1104/pp.109.145409}, abstractNote={Abstract
               Plants produce reactive oxygen species (ROS) in response to environmental stresses sending signaling cues, which, if uncontrolled, result in cell death. Like other aerobic organisms, plants have ROS-scavenging enzymes, such as superoxide dismutase (SOD), which removes superoxide anion radical (O2  −) and prevents the production and buildup of toxic free radicals. However, increasing the expression of cytosolic SODs is complex, and increasing their production in vivo has proven to be challenging. To avoid problems with endogenous regulation of gene expression, we expressed a gene from the archaeal hyperthermophile Pyrococcus furiosus that reduces O2  −. P. furiosus uses superoxide reductase (SOR) rather than SOD to remove superoxide. SOR is a thermostable enzyme that reduces O2  − in a one-electron reduction without producing oxygen. We show that P. furiosus SOR can be produced as a functional enzyme in planta and that plants producing SOR have enhanced tolerance to heat, light, and chemically induced ROS. Stress tolerance in the SOR-producing plants correlates positively with a delayed increase in ROS-sensitive transcripts and a decrease in ascorbate peroxidase activity. The SOR plants provide a good model system to study the impact of cytosolic ROS on downstream signaling in plant growth and development. Furthermore, this work demonstrates that this synthetic approach for reducing cytosolic ROS holds promise as a means for improving stress tolerance in crop plants.}, number={2}, journal={PLANT PHYSIOLOGY}, author={Im, Yang Ju and Ji, Mikyoung and Lee, Alice and Killens, Rushyannah and Grunden, Amy M. and Boss, Wendy F.}, year={2009}, month={Oct}, pages={893–904} }
 @article{ma_shor_diminshtein_yu_im_perera_lomax_boss_moran_2009, title={Phosphatidylinositol (4,5)Bisphosphate Inhibits K+-Efflux Channel Activity in NT1 Tobacco Cultured Cells}, volume={149}, ISSN={["1532-2548"]}, DOI={10.1104/pp.108.129007}, abstractNote={Abstract
               In the animal world, the regulation of ion channels by phosphoinositides (PIs) has been investigated extensively, demonstrating a wide range of channels controlled by phosphatidylinositol (4,5)bisphosphate (PtdInsP2). To understand PI regulation of plant ion channels, we examined the in planta effect of PtdInsP2 on the K+-efflux channel of tobacco (Nicotiana tabacum), NtORK (outward-rectifying K channel). We applied a patch clamp in the whole-cell configuration (with fixed “cytosolic” Ca2+ concentration and pH) to protoplasts isolated from cultured tobacco cells with genetically manipulated plasma membrane levels of PtdInsP2 and cellular inositol (1,4,5)trisphosphate: “Low PIs” had depressed levels of these PIs, and “High PIs” had elevated levels relative to controls. In all of these cells, K channel activity, reflected in the net, steady-state outward K+ currents (IK), was inversely related to the plasma membrane PtdInsP2 level. Consistent with this, short-term manipulations decreasing PtdInsP2 levels in the High PIs, such as pretreatment with the phytohormone abscisic acid (25 μ  m) or neutralizing the bath solution from pH 5.6 to pH 7, increased IK (i.e. NtORK activity). Moreover, increasing PtdInsP2 levels in controls or in abscisic acid-treated high-PI cells, using the specific PI-phospholipase C inhibitor U73122 (2.5–4 μ  m), decreased NtORK activity. In all cases, IK decreases stemmed largely from decreased maximum attainable NtORK channel conductance and partly from shifted voltage dependence of channel gating to more positive potentials, making it more difficult to activate the channels. These results are consistent with NtORK inhibition by the negatively charged PtdInsP2 in the internal plasma membrane leaflet. Such effects are likely to underlie PI signaling in intact plant cells.}, number={2}, journal={PLANT PHYSIOLOGY}, author={Ma, Xiaohong and Shor, Oded and Diminshtein, Sofia and Yu, Ling and Im, Yang Ju and Perera, Imara and Lomax, Aaron and Boss, Wendy F. and Moran, Nava}, year={2009}, month={Feb}, pages={1127–1140} }
 @article{davis_im_dubin_tomer_boss_2007, title={Arabidopsis phosphatidylinositol phosphate kinase 1 binds F-actin and recruits phosphatidylinositol 4-kinase beta 1 to the actin cytoskeleton (Retracted article. See vol. 284, pg. 16060, 2009)}, volume={282}, ISSN={["1083-351X"]}, DOI={10.1074/jbc.M611728200}, abstractNote={The actin cytoskeleton can be influenced by phospholipids and lipid-modifying enzymes. In animals the phosphatidylinositol phosphate kinases (PIPKs) are associated with the cytoskeleton through a scaffold of proteins; however, in plants such an interaction was not clear. Our approach was to determine which of the plant PIPKs interact with actin and determine whether the PIPK-actin interaction is direct. Our results indicate that AtPIPK1 interacts directly with actin and that the binding is mediated through a predicted linker region in the lipid kinase. AtPIPK1 also recruits AtPI4Kbeta1 to the cytoskeleton. Recruitment of AtPI4Kbeta1 to F-actin was dependent on the C-terminal catalytic domain of phosphatidylinositol-4-phosphate 5-kinase but did not require the presence of the N-terminal 251 amino acids, which includes 7 putative membrane occupation and recognition nexus motifs. In vivo studies confirm the interaction of plant lipid kinases with the cytoskeleton and suggest a role for actin in targeting PIPKs to the membrane.}, number={19}, journal={JOURNAL OF BIOLOGICAL CHEMISTRY}, author={Davis, Amanda J. and Im, Yang Ju and Dubin, Joshua S. and Tomer, Kenneth B. and Boss, Wendy F.}, year={2007}, month={May}, pages={14121–14131} }
 @article{im_perera_brglez_davis_stevenson-paulik_phillippy_johannes_allen_boss_2007, title={Increasing plasma membrane phosphatidylinositol(4,5)bisphosphate biosynthesis increases phosphoinositide metabolism in Nicotiana tabacum}, volume={19}, ISSN={["1532-298X"]}, DOI={10.1105/tpc.107.051367}, abstractNote={AbstractA genetic approach was used to increase phosphatidylinositol(4,5)bisphosphate [PtdIns(4,5)P2] biosynthesis and test the hypothesis that PtdInsP kinase (PIPK) is flux limiting in the plant phosphoinositide (PI) pathway. Expressing human PIPKIα in tobacco (Nicotiana tabacum) cells increased plasma membrane PtdIns(4,5)P2 100-fold. In vivo studies revealed that the rate of 32Pi incorporation into whole-cell PtdIns(4,5)P2 increased >12-fold, and the ratio of [3H]PtdInsP2 to [3H]PtdInsP increased 6-fold, but PtdInsP levels did not decrease, indicating that PtdInsP biosynthesis was not limiting. Both [3H]inositol trisphosphate and [3H]inositol hexakisphosphate increased 3-and 1.5-fold, respectively, in the transgenic lines after 18 h of labeling. The inositol(1,4,5)trisphosphate [Ins(1,4,5)P3] binding assay showed that total cellular Ins(1,4,5)P3/g fresh weight was >40-fold higher in transgenic tobacco lines; however, even with this high steady state level of Ins(1,4,5)P3, the pathway was not saturated. Stimulating transgenic cells with hyperosmotic stress led to another 2-fold increase, suggesting that the transgenic cells were in a constant state of PI stimulation. Furthermore, expressing Hs PIPKIα increased sugar use and oxygen uptake. Our results demonstrate that PIPK is flux limiting and that this high rate of PI metabolism increased the energy demands in these cells.}, number={5}, journal={PLANT CELL}, author={Im, Yang Ju and Perera, Imara Y. and Brglez, Irena and Davis, Amanda J. and Stevenson-Paulik, Jill and Phillippy, Brian Q. and Johannes, Eva and Allen, Nina S. and Boss, Wendy F.}, year={2007}, month={May}, pages={1603–1616} }
 @article{im_davis_perera_johannes_allen_boss_2007, title={The N-terminal membrane occupation and recognition nexus domain of Arabidopsis phosphatidylinositol phosphate kinase 1 regulates enzyme activity}, volume={282}, ISSN={["1083-351X"]}, DOI={10.1074/jbc.M611342200}, abstractNote={The type I B family of phosphatidylinositol phosphate kinases (PIPKs) contain a characteristic region of Membrane Occupation and Recognition Nexus (MORN) motifs at the N terminus. These MORN motifs are not found in PIPKs from other eukaryotes. To understand the impact of the additional N-terminal domain on protein function and subcellular distribution, we expressed truncated and full-length versions of AtPIPK1, one member of this family of PIPKs, in Escherichia coli and in tobacco cells grown in suspension culture. Deletion of the N-terminal MORN domain (amino acids 1–251) of AtPIPK1 increased the specific activity of the remaining C-terminal peptide (ΔMORN) >4-fold and eliminated activation by phosphatidic acid (PtdOH). PtdOH activation could also be eliminated by mutating Pro396 to Ala (P396A) in the predicted linker region between the MORN and the kinase homology domains. AtPIPK1 is product-activated and the MORN domain binds PtdIns(4,5)P2. Adding back the MORN peptide to ΔMORN or to the PtdOH-activated full-length protein increased activity ∼2-fold. Furthermore, expressing the MORN domain in vivo increased the plasma membrane PtdInsP kinase activity. When cells were exposed to hyperosmotic stress, the MORN peptide redistributed from the plasma membrane to a lower phase or endomembrane fraction. In addition, endogenous PtdInsP kinase activity increased in the endomembrane fraction of hyperosmotically stressed cells. We conclude that the MORN peptide can regulate both the function and distribution of the enzyme in a manner that is sensitive to the lipid environment.}, number={8}, journal={JOURNAL OF BIOLOGICAL CHEMISTRY}, author={Im, Yang Ju and Davis, Amanda J. and Perera, Imara Y. and Johannes, Eva and Allen, Nina S. and Boss, Wendy F.}, year={2007}, month={Feb}, pages={5443–5452} }
 @article{perera_davis_galanopilou_im_boss_2005, title={Characterization and comparative analysis of Arabidopsis phosphatidylinositol phosphate 5-kinase 10 reveals differences in Arabidopsis and human phosphatidylinositol phosphate kinases}, volume={579}, ISSN={["1873-3468"]}, DOI={10.1016/j.febslet.2005.05.018}, abstractNote={
Arabidopsis phosphatidylinositol phosphate (PtdInsP) kinase 10 (AtPIPK10; At4g01190) is shown to be a functional enzyme of the subfamily A, type I AtPtdInsP kinases. It is biochemically distinct from AtPIPK1 (At1g21980), the only other previously characterized AtPtdInsP kinase which is of the B subfamily. AtPIPK10 has the same K
m, but a 10‐fold lower V
max than AtPIPK1 and it is insensitive to phosphatidic acid. AtPIPK10 transcript is most abundant in inflorescence stalks and flowers, whereas AtPIPK1 transcript is present in all tissues. Comparative analysis of recombinant AtPIPK10 and AtPIPK1 with recombinant HsPIPKIα reveals that the Arabidopsis enzymes have roughly 200‐ and 20‐fold lower V
max/K
m, respectively. These data reveal one explanation for the longstanding mystery of the relatively low phosphatidylinositol‐(4,5)‐bisphosphate:phosphatidylinositol‐4‐phosphate ratio in terrestrial plants.}, number={16}, journal={FEBS LETTERS}, author={Perera, IY and Davis, AJ and Galanopilou, D and Im, YJ and Boss, WF}, year={2005}, month={Jun}, pages={3427–3432} }
 @article{im_ji_lee_boss_grunden_2005, title={Production of a thermostable archaeal superoxide reductase in plant cells}, volume={579}, ISSN={["1873-3468"]}, DOI={10.1016/j.febslet.2005.09.015}, abstractNote={
Pyrococcus furiosus superoxide reductase (SOR) is a thermostable archaeal enzyme that reduces superoxide without producing oxygen. When produced as a fusion protein with the green fluorescent protein in plant cells, P. furiosus SOR is located in the cytosol and nucleus. The recombinant SOR enzyme retains its function and heat stability when assayed in vitro. Importantly, expressing SOR in plant cells enhances their survival at high temperature indicating that it functions in vivo. The archaeal SOR provides a novel mechanism to reduce superoxide and demonstrates the potential for using archaeal genes to alter eukaryotic metabolism.}, number={25}, journal={FEBS LETTERS}, author={Im, YJ and Ji, MK and Lee, AM and Boss, WF and Grunden, AM}, year={2005}, month={Oct}, pages={5521–5526} }