@article{tsou_lee_allen_winter-sederoff_robertson_2012, title={An ER-targeted calcium-binding peptide confers salt and drought tolerance mediated by CIPK6 in Arabidopsis}, volume={235}, ISSN={["1432-2048"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84857634774&partnerID=MN8TOARS}, DOI={10.1007/s00425-011-1522-9}, abstractNote={Different plant organelles have high internal stores of Ca(2+) compared to the cytoplasm and could play independent roles in stress responses or signal transduction. We used a GFP fusion with the C-domain of calreticulin, which shows low-affinity, high capacity Ca(2+) binding in the ER, as a calcium-binding peptide (CBP) to specifically increase stores in the ER and nucleus. Despite the presence of a signal sequence and KDEL retention sequence, our work and previous studies (Brandizzi et al. Plant Journal 34:269-281, 2003) demonstrated both ER and nuclear localization of GFP-CBP. Under normal conditions, GFP-CBP-expressing lines had ~25% more total Ca(2+) and higher levels of chlorophyll and seed yield than wild type and GFP controls. CBP-expressing plants also had better survival under intermittent drought or high salt treatments and increased root growth. One member of the CIPK (calcineurin B-like interacting protein kinase) gene family, CIPK6, was up-regulated in CBP-expressing plants, even under non-stress conditions. A null mutation in cipk6 abolished the increased stress tolerance of CBP-transgenic plants, as well as the CBP-mediated induction of two stress-associated genes, DREB1A and RD29A, under non-stress conditions. Although this suggested that it was the induction of CIPK6, rather than localized changes in Ca(2+), that resulted in increased survival under adverse conditions, CIPK6 induction still required Ca(2+). This work demonstrates that ER (or nuclear) Ca(2+) can directly participate in signal transduction to alter gene expression. The discovery of a method for increasing Ca(2+) levels without deleterious effects on plant growth may have practical applications.}, number={3}, journal={PLANTA}, author={Tsou, Pei-Lan and Lee, Sang Yoon and Allen, Nina Stromgren and Winter-Sederoff, Heike and Robertson, Dominique}, year={2012}, month={Mar}, pages={539–552} }
 @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{burke_wilcut_allen_2007, title={Viability and in vitro germination of Johnsongrass (Sorghum halepense) pollen}, volume={21}, ISSN={["1550-2740"]}, DOI={10.1614/WT-05-171.1}, abstractNote={A high proportion of viable pollen grains must germinate to study the physiology of pollen growth to reduce the confounding effects of environmental influences on pollen germination. The objectives of this study were to evaluate the nuclear state and develop a suitable medium and culture method for in vitro germination of johnsongrass pollen. Johnsongrass pollen was trinucleate, and in vitro tests for pollen viability using Alexander's stain and a fluorochromatic reaction method (FCR) indicated johnsongrass pollen was viable (92.6 to 98.4%). A factorial treatment arrangement of four concentrations of sucrose, two concentrations of boric acid, and two concentrations of calcium nitrate were used to determine the optimum pollen-germination medium composition in suspension culture, agar culture, and cellophane membrane culture. Germination was highest in a suspension culture with a medium containing 0.3 M sucrose, 2.4 mM boric acid, and 3 mM calcium nitrate. Pollen germination using this medium was 78.9% when anthers were harvested just before anthesis.}, number={1}, journal={WEED TECHNOLOGY}, author={Burke, Ian C. and Wilcut, John W. and Allen, Nina S.}, year={2007}, pages={23–29} }
 @article{gupton_collings_allen_2006, title={Endoplasmic reticulum targeted GFP reveals ER organization in tobacco NT-1 cells during cell division}, volume={44}, ISSN={["0981-9428"]}, DOI={10.1016/j.plaphy.2006.03.003}, abstractNote={The endoplasmic reticulum (ER) of plant cells undergoes a drastic reorganization during cell division. In tobacco NT-1 cells that stably express a GFP construct targeted to the ER, we have mapped the reorganization of ER that occurs during mitosis and cytokinesis with confocal laser scanning microscopy. During division, the ER and nuclear envelope do not vesiculate. Instead, tubules of ER accumulate around the chromosomes after the nuclear envelope breaks down, with these tubules aligning parallel to the microtubules of the mitotic spindle. In cytokinesis, the phragmoplast is particularly rich in ER, and the transnuclear channels and invaginations present in many interphase cells appear to develop from ER tubules trapped in the developing phragmoplast. Drug studies, using oryzalin and latrunculin to disrupt the microtubules and actin microfilaments, respectively, demonstrate that during division, the arrangement of ER is controlled by microtubules and not by actin, which is the reverse of the situation in interphase cells.}, number={2-3}, journal={PLANT PHYSIOLOGY AND BIOCHEMISTRY}, author={Gupton, S. L. and Collings, D. A. and Allen, N. S.}, year={2006}, pages={95–105} }
 @article{vincent_chua_nogue_fairbrother_mekeel_xu_allen_bibikova_gilroy_bankaitis_2005, title={A Sec14p-nodulin domain phosphatidylinositol transfer protein polarizes membrane growth of Arabidopsis thaliana root hairs}, volume={168}, ISSN={["1540-8140"]}, DOI={10.1083/jcb.200412074}, abstractNote={Phosphatidylinositol (PtdIns) transfer proteins (PITPs) regulate signaling interfaces between lipid metabolism and membrane trafficking. Herein, we demonstrate that AtSfh1p, a member of a large and uncharacterized Arabidopsis thaliana Sec14p-nodulin domain family, is a PITP that regulates a specific stage in root hair development. AtSfh1p localizes along the root hair plasma membrane and is enriched in discrete plasma membrane domains and in the root hair tip cytoplasm. This localization pattern recapitulates that visualized for PtdIns(4,5)P2 in developing root hairs. Gene ablation experiments show AtSfh1p nullizygosity compromises polarized root hair expansion in a manner that coincides with loss of tip-directed PtdIns(4,5)P2, dispersal of secretory vesicles from the tip cytoplasm, loss of the tip f-actin network, and manifest disorganization of the root hair microtubule cytoskeleton. Derangement of tip-directed Ca2+ gradients is also apparent and results from isotropic influx of Ca2+ from the extracellular milieu. We propose AtSfh1p regulates intracellular and plasma membrane phosphoinositide polarity landmarks that focus membrane trafficking, Ca2+ signaling, and cytoskeleton functions to the growing root hair apex. We further suggest that Sec14p-nodulin domain proteins represent a family of regulators of polarized membrane growth in plants.}, number={5}, journal={JOURNAL OF CELL BIOLOGY}, author={Vincent, P and Chua, M and Nogue, F and Fairbrother, A and Mekeel, H and Xu, Y and Allen, N and Bibikova, TN and Gilroy, S and Bankaitis, VA}, year={2005}, month={Feb}, pages={801–812} }
 @article{weerasinghe_bird_allen_2005, title={Root-knot nematodes and bacterial Nod factors elicit common signal transduction events in Lotus japonicus}, volume={102}, ISSN={["0027-8424"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-14544295731&partnerID=MN8TOARS}, DOI={10.1073/pnas.0407926102}, abstractNote={
            The symbiosis responsible for nitrogen fixation in legume root nodules is initiated by rhizobial signaling molecules [Nod factors (NF)]. Using transgenically tagged microtubules and actin, we dynamically profiled the spatiotemporal changes in the cytoskeleton of living
            Lotus japonicus
            root hairs, which precede root-hair deformation and reflect one of the earliest host responses to NF. Remarkably, plant-parasitic root-knot nematodes (RKN) invoke a cytoskeletal response identical to that seen in response to NF and induce root-hair waviness and branching in legume root hairs via a signal able to function at a distance. Azide-killed nematodes do not produce this signal. A similar response to RKN was seen in tomato. Aspects of the host responses to RKN were altered or abolished by mutations in the NF receptor genes
            nfr1
            ,
            nfr5
            , and
            symRK
            , suggesting that RKN produce a molecule with functional equivalence to NF, which we name NemF. Because the ability of RKN to establish feeding sites and reproduce was markedly reduced in the mutant lines, we propose that RKN have adapted at least part of the symbiont-response pathway to enhance their parasitic ability.
          }, number={8}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Weerasinghe, RR and Bird, DM and Allen, NS}, year={2005}, month={Feb}, pages={3147–3152} }
 @article{moyer-henry_silva_macfall_johannes_allen_goldfarb_rufty_2005, title={Accumulation and localization of aluminium in root tips of loblolly pine seedlings and the associated ectomycorrhiza Pisolithus tinctorius}, volume={28}, ISSN={["1365-3040"]}, DOI={10.1111/j.1365-3040.2004.01240.x}, abstractNote={ABSTRACTEvidence from past studies suggests that loblolly pine may be tolerant of Al. The experiments described in this manuscript were initiated to examine Al tolerance and Al accumulation in the pine root and the degree of Al accumulation in fungal hyphae when pine roots were colonized with the ectomycorrhiza Pisolithus tinctorius. The experiments used lumogallion staining and confocal microscopy to localize Al in root and fungal structures. The results clearly showed that loblolly pine seedlings were highly resistant to Al. A decrease in primary root extension could not be detected until Al+3 activities approached 40 µmol L−1, and extension was suppressed only 30% at an Al+3 activity of 580 µmol L−1. This contrasted with the response of the Al‐sensitive ‘check’ species soybean, where primary root extension was severely restricted at Al+3 activities lower than 5 µmol L−1. Tissue Al measurements and lumogallion fluorescence of longitudinal sections of the pine root tip indicated that tolerance was associated with both Al exclusion from the tip region and compartmentalization of absorbed Al in peripheral cell areas outside of the meristem. In lateral roots colonized with ectomycorrhizae, lumogallion fluorescence showed that large amounts of Al accumulated at the fungal mantle and in areas with the Hartig net. At higher magnification, lumogallion indicated substantial Al accumulation inside hyphae. Little Al could be detected in lateral root cells. The results show that pine possesses multiple mechanisms that can contribute to Al tolerance in acid field soils.}, number={2}, journal={PLANT CELL AND ENVIRONMENT}, author={Moyer-Henry, K and Silva, I and Macfall, J and Johannes, E and Allen, N and Goldfarb, B and Rufty, T}, year={2005}, month={Feb}, pages={111–120} }
 @article{turner_sit_callaway_allen_lommel_2004, title={Red clover necrotic mosaic virus replication proteins accumulate at the endoplasmic reticulum}, volume={320}, ISSN={["0042-6822"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-1542285421&partnerID=MN8TOARS}, DOI={10.1016/j.virol.2003.12.006}, abstractNote={Red clover necrotic mosaic virus (RCNMV) encodes N-terminally overlapping proteins of 27 and 88 kDa (p27 and p88) known to be required for replication. Green fluorescent protein (GFP) fusions were used to visualize the location of p27 and p88 within Nicotiana benthamiana cells. GFP:p27 fusions localized to the endoplasmic reticulum (ER), co-localized with ER-targeted yellow fluorescent protein and caused membrane restructuring and proliferation. Cellular fractionation of virus-inoculated N. benthamiana leaves confirmed the association of p27 with ER membranes. GFP:p88 fusions also localized to the ER and co-localized with GFP:p27. Both fusion proteins co-localize to the cortical and cytoplasmic ER and were associated with invaginations of the nuclear envelope. Independent accumulation in, and perturbation of, the ER suggests that p27 and p88 function together in the replication complex. This is the first report of a member of the Tombusviridae replicating in association with the ER.}, number={2}, journal={VIROLOGY}, publisher={Elsevier BV}, author={Turner, KA and Sit, TL and Callaway, AS and Allen, NS and Lommel, SA}, year={2004}, month={Mar}, pages={276–290} }
 @article{allen_chattaraj_collings_johannes_2003, title={Gravisensing: Ionic responses, cytoskeleton and amyloplast behavior}, volume={32}, ISBN={["*************"]}, ISSN={["0273-1177"]}, DOI={10.1016/S0273-1177(03)00492-7}, number={8}, journal={SPACE LIFE SCIENCES: GRAVITATIONAL BIOLOGY: 2002}, author={Allen, NS and Chattaraj, P and Collings, D and Johannes, E}, year={2003}, pages={1631–1637} }
 @article{weerasinghe_collings_johannes_allen_2003, title={The distributional changes and role of microtubules in Nod factor-challenged Medicago sativa root hairs}, volume={218}, ISSN={["1432-2048"]}, DOI={10.1007/s00425-003-1097-1}, abstractNote={The normal tip-growing pattern exhibited by root hairs of legumes is disrupted when the hair is exposed to Nod factors generated by compatible bacteria capable of inducing nodule formation. Since microtubules (MTs) play an important role in regulating directionality and stability of apical growth in root hairs [T.N. Bibikova et al. (1999) Plant J 17:657-665], we examined the possibility that Nod factors might affect the MT distribution patterns in root hairs of Medicago sativa L. We observed that Nod factor application caused rapid changes in the pattern of MTs starting as early as 3 min after perfusion. Within 3 to 10 min after Nod factor application, first endoplasmic and then cortical MTs depolymerised, initially at the proximal ends of cells. Twenty minutes after exposure to Nod factors, a transverse band of microtubules was seen behind the tip, while almost all other MTs had depolymerised. By 30 min, very few MTs remained in the root hair and yet by 1 h the MT cytoskeleton re-formed. When Nod factors were applied in the presence of 10 microM oryzalin or 5 microM taxol, the MTs appeared disintegrated while the morphological effects, such as bulging and branching, became enhanced. Compared to the treatments with oryzalin or taxol alone, the combinatory treatments exhibited higher growth rates. Since microtubule reorganization is one of the earliest measurable events following Nod factor application we conclude that microtubules have an important role in the early phases of the signalling cascade. Microtubule involvement could be direct or a consequence of Nod factor-induced changes in ion levels.}, number={2}, journal={PLANTA}, author={Weerasinghe, RR and Collings, DA and Johannes, E and Allen, NS}, year={2003}, month={Dec}, pages={276–287} }
 @article{pline_edmisten_oliver_wilcut_wells_allen_2002, title={Use of digital image analysis, viability stains, and germination assays to estimate conventional and glyphosate-resistant cotton pollen viability}, volume={42}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci2002.2193}, abstractNote={AbstractBecause the success of labor‐intensive hand crosses by breeders is dependent upon pollen viability, quick, simple, and inexpensive methods for viability assessment are of interest. Four such cotton pollen viability assays were compared to determine differences in viability estimates, and relative accuracy by correlation to seed set. The methods compared were Brewbaker & Kwack (B & K) medium, B & K medium plus aniline blue, a fluorochromatic reaction method (FCR), and Alexander's stain. Additionally, digital images of germinated pollen grains were analyzed by means of morphometry software to quantify pollen tube area per pollen grain, as a proposed additional method of assessing viability. Pollen from conventional, nontreated glyphosate‐resistant (GR) and glyphosate‐treated GR cotton (Gossypium hirsutum L.) plants was tested by each method. Glyphosate treatments to GR cotton reduced pollen viability and corresponding seed set in all methods tested. Pollen germination measured by the B & K method was most closely related to seed set per boll, while Alexander's stain gave the highest estimates of viability. The FCR method indicated that many pollen grains from glyphosate‐treated GR cotton were irregularly shaped and only partially flourescein diacetate (FD) stained. All methods tested showed similar high correlation (0.7–0.8) of pollen viability to seed set. Morphometric analysis of digital images of germinated pollen found the greatest pollen tube area to pollen grain ratio with B & K medium + 30 mM sucrose. Because the B & K method most closely predicted the linear magnitude of seed set reduction to reduced pollen viability, allowed the use of morphometry software analysis, and was one of the simplest and least equipment‐demanding methods, it may provide broad utility for those assessing cotton pollen viability.}, number={6}, journal={CROP SCIENCE}, author={Pline, WA and Edmisten, KL and Oliver, T and Wilcut, JW and Wells, R and Allen, NS}, year={2002}, pages={2193–2200} }
 @article{johannes_collings_rink_allen_2001, title={Cytoplasmic pH dynamics in maize pulvinal cells induced induced by gravity vector changes}, volume={127}, ISSN={["1532-2548"]}, DOI={10.1104/pp.127.1.119}, abstractNote={Abstract
               In maize (Zea mays) and other grasses, changes in orientation of stems are perceived by pulvinal tissue, which responds to the stimulus by differential growth resulting in upward bending of the stem. The amyloplast-containing bundle sheath cells are the sites of gravity perception, although the initial steps of gravity perception and transmission remain unclear. In columella cells of Arabidopsis roots, we previously found that cytoplasmic pH (pHc) is a mediator in early gravitropic signaling (A.C. Scott, N.S. Allen [1999] Plant Physiol 121: 1291–1298). The question arises whether pHc has a more general role in signaling gravity vector changes. Using confocal ratiometric imaging and the fluorescent pH indicator carboxy seminaphtorhodafluor acetoxymethyl ester acetate, we measured pHc in the cells composing the maize pulvinus. When stem slices were gravistimulated and imaged on a horizontally mounted confocal microscope, pHc changes were only apparent within the bundle sheath cells, and not in the parenchyma cells. After turning, cytoplasmic acidification was observed at the sides of the cells, whereas the cytoplasm at the base of the cells where plastids slowly accumulated became more basic. These changes were most apparent in cells exhibiting net amyloplast sedimentation. Parenchyma cells and isolated bundle sheath cells did not show any gravity-induced pHc changes although all cell types responded to external stimuli in the predicted way: Propionic acid and auxin treatments induced acidification, whereas raising the external pH caused alkalinization. The results suggest that pHc has an important role in the early signaling pathways of maize stem gravitropism.}, number={1}, journal={PLANT PHYSIOLOGY}, author={Johannes, E and Collings, DA and Rink, JC and Allen, NS}, year={2001}, month={Sep}, pages={119–130} }
 @article{collings_zsuppan_allen_blancaflor_2001, title={Demonstration of prominent actin filaments in the root columella}, volume={212}, ISSN={["1432-2048"]}, DOI={10.1007/s004250000406}, abstractNote={The distribution of actin filaments within the gravity-sensing columella cells of plant roots remains poorly understood, with studies over numerous years providing inconsistent descriptions of actin organization in these cells. This uncertainty in actin organization, and thus in actin's role in graviperception and gravisignaling, has led us to investigate actin arrangements in the columella cells of Zea mays L., Medicago truncatula Gaertn., Linum usitatissiilium L. and Nicotianla benthamiana Domin. Actin organization was examined using a combination of optimized immunofluorescence techniques, and an improved fluorochrome-conjugated phalloidin labeling method reliant on 3-maleimidobenzoyl-N-hydroxy-succinimide ester (MBS) cross-linking combined with glycerol permeabilization. Confocal microscopy of root sections labeled with anti-actin antibodies revealed patterns suggestive of actin throughout the columella region. These patterns included short and fragmented actin bundles, fluorescent rings around amyloplasts and intense fluorescence originating from the nucleus. Additionally, confocal microscopy of MBS-stabilized and Alexa Fluor-phalloidin-labeled root sections revealed a previously undetected state of actin organization in the columella. Discrete actin structures surrounded the amyloplasts and prominent actin cables radiated from the nuclear surface toward the cell periphery. Furthermore, the cortex of the columella cells contained fine actin bundles (or single filaments) that had a predominant transverse orientation. We also used confocal microscopy of plant roots expressing endoplasmic reticulum (ER)-targeted green fluorescent protein to demonstrate rapid ER movements within the columella cells, suggesting that the imaged actin network is functional. The successful identification of discrete actin structures in the root columella cells forms the perception and signaling.}, number={3}, journal={PLANTA}, author={Collings, DA and Zsuppan, G and Allen, NS and Blancaflor, EB}, year={2001}, month={Feb}, pages={392–403} }
 @inproceedings{johannes_allen_2001, title={Dynamics of amyloplast sedimentation in pulvinal bundle sheath cells of maize}, volume={12}, number={2001 Nov}, booktitle={Molecular Biology of the Cell}, author={Johannes, E. M. and Allen, N. S.}, year={2001}, pages={910} }
 @article{silva_smyth_moxley_carter_allen_rufty_2000, title={Aluminum accumulation at nuclei of cells in the root tip. Fluorescence detection using lumogallion and confocal laser scanning microscopy}, volume={123}, ISSN={["1532-2548"]}, DOI={10.1104/pp.123.2.543}, abstractNote={Abstract
               The mechanistic basis for Al toxicity effects on root growth is still a matter of speculation, but it almost certainly involves decreased cell division at the root apex. In this series of experiments, we attempt to determine whether Al enters meristematic cells and binds to nuclei when roots are exposed to a low Al3+ activity in solution. The methodology involved the use of the Al-sensitive stain lumogallion (3-[2,4 dihydroxyphenylazo]-2-hydroxy-5-chlorobenzene sulfonic acid), the DNA stain 4′,6-diamino-phenylindole, and confocal laser scanning microscopy. Soybean (Glycine max L. Merr.) cv Young (Al-sensitive) and PI 416937 (Al-tolerant) genotypes were exposed to 1.45 μm Al3+ for periods ranging from 30 min to 72 h, and then washed with 10 mm citrate to remove apoplastic Al. Fluorescence images show that within 30 min Al entered cells of the sensitive genotype and accumulated at nuclei in the meristematic region of the root tip. Substantial Al also was present at the cell periphery. The images indicated that the Al-tolerant genotype accumulated lower amounts of Al in meristematic and differentiating cells of the root tip and their cell walls. Collectively, the results support an important role for exclusion in Al tolerance.}, number={2}, journal={PLANT PHYSIOLOGY}, author={Silva, IR and Smyth, TJ and Moxley, DF and Carter, TE and Allen, NS and Rufty, TW}, year={2000}, month={Jun}, pages={543–552} }
 @article{collings_carter_rink_scott_wyatt_allen_2000, title={Plant nuclei can contain extensive grooves and invaginations}, volume={12}, DOI={10.2307/3871239}, number={12}, journal={Plant Cell}, author={Collings, D. A. and Carter, C. N. and Rink, J. C. and Scott, A. C. and Wyatt, S. E. and Allen, N. S.}, year={2000}, pages={2425–2439} }
 @article{scott_allen_1999, title={Changes in cytosolic pH within Arabidopsis root columella cells play a key role in the early signaling pathway for root gravitropism}, volume={121}, ISSN={["1532-2548"]}, DOI={10.1104/pp.121.4.1291}, abstractNote={Abstract
               Ratiometric wide-field fluorescence microscopy with 1′,7′- bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF)-dextran demonstrated that gravistimulation leads to rapid changes in cytoplasmic pH (pHc) in columella cells of Arabidopsis roots. The pHc of unstimulated columella cells in tiers 2 and 3, known sites of graviperception (E.B. Blancaflor, J.B. Fasano, S. Gilroy [1998] Plant Physiol 116: 213–222), was 7.22 ± 0.02 pH units. Following gravistimulation, the magnitude and direction of pHc changes in these cells depended on their location in the columella. Cells in the lower side of tier 2 became more alkaline by 0.4 unit within 55 s of gravistimulation, whereas alkalinization of the cells on the upper side was slower (100 s). In contrast, all cells in tier 3 acidified by 0.4 pH unit within 480 s after gravistimulation. Disrupting these pHc changes in the columella cells using pHc modifiers at concentrations that do not affect root growth altered the gravitropic response. Acidifying agents, including bafilomycin A1, enhanced curvature, whereas alkalinizing agents disrupted gravitropic bending. These results imply that pHc changes in the gravisensing cells and the resultant pH gradients across the root cap are important at an early stage in the signal cascade leading to the gravitropic response.}, number={4}, journal={PLANT PHYSIOLOGY}, author={Scott, AC and Allen, NS}, year={1999}, month={Dec}, pages={1291–1298} }
 @article{scott_wyatt_tsou_robertson_allen_1999, title={Model system for plant cell biology: GFP imaging in living onion epidermal cells}, volume={26}, ISSN={["1940-9818"]}, DOI={10.2144/99266st04}, abstractNote={ The ability to visualize organelle localization and dynamics is very useful in studying cellular physiological events. Until recently, this has been accomplished using a variety of staining methods. However, staining can give inaccurate information due to nonspecific staining, diffusion of the stain or through toxic effects. The ability to target green fluorescent protein (GFP) to various organelles allows for specific labeling of organelles in vivo. The disadvantages of GFP thus far have been the time and money involved in developing stable transformants or maintaining cell cultures for transient expression. In this paper, we present a rapid transient expression system using onion epidermal peels. We have localized GFP to various cellular compartments (including the cell wall) to illustrate the utility of this method and to visualize dynamics of these compartments. The onion epidermis has large, living, transparent cells in a monolayer, making them ideal for visualizing GFP. This method is easy and inexpensive, and it allows for testing of new GFP fusion proteins in a living tissue to determine deleterious effects and the ability to express before stable transformants are attempted. }, number={6}, journal={BIOTECHNIQUES}, author={Scott, A and Wyatt, S and Tsou, PL and Robertson, D and Allen, NS}, year={1999}, month={Jun}, pages={1125-+} }
 @article{jones_allen_willingham_lewis_1999, title={Modified LDLs induce and bind to membrane ruffles on macrophages}, volume={255}, DOI={10.1002/(sici)1097-0185(19990501)255:1<44::aid-ar6>3.3.co;2-z}, abstractNote={Macrophage foam cell formation in vitro requires uptake of modified low density lipoproteins (LDL) such as acetylated LDL (AcLDL) and moderately oxidized LDL (OxLDL), or beta-migrating very low density lipoprotein (βVLDL), a naturally occurring lipoprotein. Incubation of macrophages with AcLDL and OxLDL resulted in stimulation of membrane ruffle formation, while βVLDL primarily resulted in increased numbers of microvilli. Time-lapse Allen video enhanced contrast differential interference contrast (AVEC-DIC) light microscopy and correlative whole mount intermediate-voltage transmission electron microscopy (IVEM) was used to examine the dynamics of AcLDL stimulated membrane ruffling and membrane ruffle ultrastructure. Stereo 3D surface replicas confirmed that AcLDL bound to these AcLDL-induced membrane ruffles. Quantification of the plasma membrane surface area after incubation with AcLDL, βVLDL or LDL confirmed that AcLDL stimulated membrane ruffling, while βVLDL and LDL stimulated microvilli formation. These studies suggest that modified LDLs induce circular membrane ruffles and modified LDLs bind to these ligand-induced membrane ruffles. Anat Rec 255:44–56, 1999. © 1999 Wiley-Liss, Inc.}, number={1}, journal={Anatomical Record}, author={Jones, N. L. and Allen, N. S. and Willingham, M. C. and Lewis, J. C.}, year={1999}, pages={44–56} }
 @article{collings_winter_wyatt_allen_1998, title={Growth dynamics and cytoskeleton organization during stem maturation and gravity-induced stem bending in Zea mays L.}, volume={207}, ISSN={["1432-2048"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032435367&partnerID=MN8TOARS}, DOI={10.1007/s004250050480}, abstractNote={Characterization of gravitropic bending in the maize stem pulvinus, a tissue that functions specifically in gravity responses, demonstrates that the pulvinus is an ideal system for studying gravitropism. Gravistimulation during the second of three developmental phases of the pulvinus induces a gradient of cell elongation across the non-growing cells of the pulvinus, with the most elongation occurring on the lower side. This cell elongation is spatially and temporally separated from normal internodal cell elongation. The three characterized growth phases in the pulvinus correspond closely to a specialized developmental sequence in which structural features typical of cells not fully matured are retained while cell maturation occurs in surrounding internodal and nodal tissue. For example, the lignification of supporting tissue and rearrangement of transverse microtubules to oblique that occur in the internode when cell elongation ceases are delayed for up to 10 d in the adjacent cells of the pulvinus, and only occurs as a pulvinus loses its capacity to respond to gravistimulation. Gravistimulation does not modify this developmental sequence. Neither wall lignification nor rearrangement of transverse microtubules occurs in the rapidly elongating lower side or non-responsive upper side of the pulvinus until the pulvinus loses the capacity to bend further. Gravistimulation does, however, lead to the formation of putative pit fields within the expanding cells of the pulvinus.}, number={2}, journal={PLANTA}, author={Collings, DA and Winter, H and Wyatt, SE and Allen, NS}, year={1998}, month={Dec}, pages={246–258} }
 @article{collings_asada_allen_shibaoka_1998, title={Plasma membrane-associated actin in bright yellow 2 tobacco cells - Evidence for interaction with microtubules}, volume={118}, ISSN={["1532-2548"]}, DOI={10.1104/pp.118.3.917}, abstractNote={Abstract
               Plasma membrane ghosts form when plant protoplasts attached to a substrate are lysed to leave a small patch of plasma membrane. We have identified several factors, including the use of a mildly acidic actin stabilization buffer and the inclusion of glutaraldehyde in the fixative, that allow immunofluorescent visualization of extensive cortical actin arrays retained on membrane ghosts made from tobacco (Nicotiana tabacum L.) suspension-cultured cells (line Bright Yellow 2). Normal microtubule arrays were also retained using these conditions. Membrane-associated actin is random; it exhibits only limited coalignment with the microtubules, and microtubule depolymerization in whole cells before wall digestion and ghost formation has little effect on actin retention. Actin and microtubules also exhibit different sensitivities to the pH and K+ and Ca2+ concentrations of the lysis buffer. There is, however, strong evidence for interactions between actin and the microtubules at or near the plasma membrane, because both ghosts and protoplasts prepared from taxol-pretreated cells have microtubules arranged in parallel arrays and an increased amount of actin coaligned with the microtubules. These experiments suggest that the organization of the cortical actin arrays may be dependent on the localization and organization of the microtubules.}, number={3}, journal={PLANT PHYSIOLOGY}, author={Collings, DA and Asada, T and Allen, NS and Shibaoka, H}, year={1998}, month={Nov}, pages={917–928} }
 @inproceedings{allen_moxley_collings_holzwarth_1998, title={Polarization modulation DIC microscopy: an improvement for video microscopy}, booktitle={Proceedings of the Electron Microscopy Society of America, 1998}, author={Allen, N. S. and Moxley, D. and Collings, D. and Holzwarth, G.}, year={1998}, pages={130–131} }
 @article{collings_winter_allen_1997, title={Cytoskeletal organisation in gravistimulated maize stems}, volume={16}, number={1997}, journal={Current Topics in Plant Biochemistry and Physiology}, author={Collings, D. and Winter, H. and Allen, N.}, year={1997}, pages={88} }
 @article{holzwarth_webb_kubinski_allen_1997, title={Improving DIC microscopy with polarization modulation}, volume={188}, ISSN={["0022-2720"]}, DOI={10.1046/j.1365-2818.1997.2500807.x}, abstractNote={It is demonstrated experimentally, as well as analytically, that when the polarization of the light incident upon the first Nomarski–Wollaston prism in a differential interference contrast (DIC) light microscope is switched by 90°, image highlights are changed into shadows and vice versa. Using an inexpensive ferroelectric liquid‐crystal modulator, which is easily installed in the microscope, this switching can be done at 30 frames s−1, synchronized to the camera. Subtraction of alternate digitized frames generates a stream of images in which contrast is doubled, compared with conventional video‐enhanced DIC, while image defects and noise tend to cancel. Subtraction of alternate images is carried out efficiently by frame buffer operations and amounts to massively parallel synchronous detection. The new method eliminates the problems inherent in obtaining a separate background image, as required by current video‐enhanced DIC practice, without loss of resolution.}, journal={JOURNAL OF MICROSCOPY-OXFORD}, author={Holzwarth, G and Webb, SC and Kubinski, DJ and Allen, NS}, year={1997}, month={Dec}, pages={249–254} }