Erik Nielsen

University of Michigan–Ann Arbor

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Daniel P. Schachtman

University of Nebraska–Lincoln

Mary L. Preuss

Webster University

Fangwei Gu

Sinopec (China)

Christopher G. P. Taylor

University of Warwick

Jiyuan Yang

St. Jude Children's Research Hospital

Amy L. Szumlanski

University of Michigan–Ann Arbor

Yaodong Yang

Chinese Academy of Tropical Agricultural Sciences

Ulrich Z. Hammes

Technical University of Munich

Sean Brawley

University of Wollongong

Heather B. Mayes

National Renewable Energy Laboratory

Cooperative Institutions

University of Michigan–Ann Arbor

University of Nottingham

Donald Danforth Plant Science Center

Max Planck Society

Ghent University

Michigan State University

Howard Hughes Medical Institute

South China Agricultural University

Sandia National Laboratories California

Vlaams Instituut voor Biotechnologie

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Lectures, 417: Acetoin synthesis in Nicotiana plumbaginifolia cultured cells

Giuseppe Forlani B. Parisi Erik Nielsen

Acetoin

Source

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Definition of IgG- and albumin-binding regions of streptococcal protein G.

Journal of Biological Chemistry (1987)

Bo Åkerström Erik Nielsen Lars Björck

Protein G, the immunoglobin G-binding surface protein of group C and G streptococci, also binds serum albumin. The albumin-binding site on protein G is distinct from the immunoglobulin G-binding site. By mild acid hydrolysis of the papain-liberated protein G fragment (35 kDa), a 28-kDa fragment was produced which retained full immunoglobulin G-binding activity (determined by Scatchard plotting) but had lost all albumin-binding capacity. A protein G (65 kDa), isolated after cloning and expression of the protein G gene in Escherichia coli, had comparable affinity to immunoglobulin G (5-10 X 10(10)M-1), but much higher affinity to albumin than the 35- and 28-kDa protein G fragments (31, 2.6, and 0 X 10(9)M-1, respectively). The amino-terminal amino acid sequences of the 65-, 35-, and 28-kDa fragments allowed us to exactly locate the three fragments in an overall sequence map of protein G, based on the partial gene sequences published by Guss et al. (Guss, B., Eliasson, M., Olsson, A., Uhlen, M., Frej, A.-K., Jornvall, H., Flock, J.-I., and Lindberg, M. (1986) EMBO J. 5, 1567-1575) and Fahnestock et al. (Fahnestock, S. R., Alexander, P., Nagle, J., and Filpula, D. (1986) J. Bacteriol. 167, 870-880). In this map could then be deduced the location of three homologous albumin-binding regions and three homologous immunoglobulin G-binding regions.

Protein G

Protein A/G

Fragment crystallizable region

Human serum albumin

10.1016/s0021-9258(19)76438-2

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Citations (128)

Recruitment of PLANT U-BOX13 and the PI4Kβ1/β2 Phosphatidylinositol-4 Kinases by the Small GTPase RabA4B Plays Important Roles during Salicylic Acid-Mediated Plant Defense Signaling in Arabidopsis

The Plant Cell (2015)

Vincenzo Antignani Amy L. Klocko Gwangbae Bak Suma D. Chandrasekaran Taylor K. Dunivin

Abstract Protection against microbial pathogens involves the activation of cellular immune responses in eukaryotes, and this cellular immunity likely involves changes in subcellular membrane trafficking. In eukaryotes, members of the Rab GTPase family of small monomeric regulatory GTPases play prominent roles in the regulation of membrane trafficking. We previously showed that RabA4B is recruited to vesicles that emerge from trans-Golgi network (TGN) compartments and regulates polarized membrane trafficking in plant cells. As part of this regulation, RabA4B recruits the closely related phosphatidylinositol 4-kinase (PI4K) PI4Kβ1 and PI4Kβ2 lipid kinases. Here, we identify a second Arabidopsis thaliana RabA4B-interacting protein, PLANT U-BOX13 (PUB13), which has recently been identified to play important roles in salicylic acid (SA)-mediated defense signaling. We show that PUB13 interacts with RabA4B through N-terminal domains and with phosphatidylinositol 4-phosphate (PI-4P) through a C-terminal armadillo domain. Furthermore, we demonstrate that a functional fluorescent PUB13 fusion protein (YFP-PUB13) localizes to TGN and Golgi compartments and that PUB13, PI4Kβ1, and PI4Kβ2 are negative regulators of SA-mediated induction of pathogenesis-related gene expression. Taken together, these results highlight a role for RabA4B and PI-4P in SA-dependent defense responses.

Small GTPase

Rab

10.1105/tpc.114.134262

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Phosphatidylinositol 4-Phosphate is Required for Tip Growth in Arabidopsis thaliana

Plant cell monographs (2009)

Amy L. Szumlanski Erik Nielsen

Tip growth

Root hair

10.1007/978-3-642-03873-0_4

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Investigation of the functional role of CSLD proteins in plant cell wall deposition

Erik Nielsen

The overall goal of this research proposal was to characterize the molecular machinery responsible for polarized secretion of cell wall components in Arabidopsis thaliana. We have used the polarized expansion that occurs during root hair cell growth to identify membrane trafficking pathways involved in polarized secretion of cell wall components to the expanding tips of these cells, and we have recently shown that CSLD3 is preferentially targeted to the apical plasma membranes in root hair cells, where it plays essential roles during cell wall deposition in these cells. The specific aims of the project are designed to answer the following objective: Identification of the cell wall polysaccharide class that CSLD proteins synthesize.

Plant cell

Root hair

Cell membrane

10.2172/1409677

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ROOT HAIR DEFECTIVE4Encodes a Phosphatidylinositol-4-Phosphate Phosphatase Required for Proper Root Hair Development inArabidopsis thaliana

The Plant Cell (2008)

Julie M. Thole Joop E. M. Vermeer Yanling Zhang Theodorus W. J. Gadella Erik Nielsen

Polarized expansion of root hair cells in Arabidopsis thaliana is improperly controlled in root hair-defective rhd4-1 mutant plants, resulting in root hairs that are shorter and randomly form bulges along their length. Using time-lapse fluorescence microscopy in rhd4-1 root hairs, we analyzed membrane dynamics after labeling with RabA4b, a marker for polarized membrane trafficking in root hairs. This revealed stochastic loss and recovery of the RabA4b compartment in the tips of growing root hairs, consistent with a role for the RHD4 protein in regulation of polarized membrane trafficking in these cells. The wild-type RHD4 gene was identified by map-based cloning and was found to encode a Sac1p-like phosphoinositide phosphatase. RHD4 displayed a preference for phosphatidylinositol-4-phosphate [PI(4)P] in vitro, and rhd4-1 roots accumulated higher levels of PI(4)P in vivo. In wild-type root hairs, PI(4)P accumulated primarily in a tip-localized plasma membrane domain, but in rhd4-1 mutants, significant levels of PI(4)P were detected associated with internal membranes. A fluorescent RHD4 fusion protein localized to membranes at the tips of growing root hairs. We propose that RHD4 is selectively recruited to RabA4b-labeled membranes that are involved in polarized expansion of root hair cells and that, in conjunction with the phosphoinositide kinase PI-4Kbeta1, RHD4 regulates the accumulation of PI(4)P on membrane compartments at the tips of growing root hairs.

Root hair

Root (linguistics)

10.1105/tpc.107.054304

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Citations (155)

AtCAT6, a sink‐tissue‐localized transporter for essential amino acids in Arabidopsis

The Plant Journal (2006)

Ulrich Z. Hammes Erik Nielsen Loren Honaas Christopher G. P. Taylor Daniel P. Schachtman

Summary Amino acids represent the major form of reduced nitrogen that is transported in plants. Amino acid transporters in plants often show tissue‐specific expression patterns and are used by plants to transport these metabolites from source to sink during development and under changing environmental conditions. We identified one amino acid transporter, AtCAT6, which is expressed in sink tissues such as lateral root primordia, flowers and seeds. Additionally AtCAT6 was induced during infestation of roots by the plant‐parasitic root‐knot nematode, Meloidogyne incognita . Quantitative reverse‐transcriptase PCR revealed nematode inducibility throughout the duration of nematode infestation and in nematode‐induced feeding sites. Promoter analyses confirmed expression in endogenous sink tissues and nematode‐induced feeding sites. In Xenopus oocytes, AtCAT6 mediated electrogenic transport of proteinogenic as well as non‐proteinogenic amino acids with moderate affinity. AtCAT6 transported large, neutral and cationic amino acids in preference to other amino acids. Knockout mutants of this transporter failed to grow on medium containing l ‐glutamine as the sole nitrogen source. Our data suggest that AtCAT6 plays a role in supplying amino acids to sink tissues of plants and nematode‐induced feeding structures.

Amino acid transporter

10.1111/j.1365-313x.2006.02880.x

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Citations (124)

Targeting and Regulation of Cell Wall Synthesis During Tip Growth in Plants

Journal of Integrative Plant Biology (2013)

Fangwei Gu Erik Nielsen

Abstract Root hairs and pollen tubes are formed through tip growth, a process requiring synthesis of new cell wall material and the precise targeting and integration of these components to a selected apical plasma membrane domain in the growing tips of these cells. Presence of a tip‐focused calcium gradient, control of actin cytoskeleton dynamics, and formation and targeting of secretory vesicles are essential to tip growth. Similar to cells undergoing diffuse growth, cellulose, hemicelluloses, and pectins are also deposited in the growing apices of tip‐growing cells. However, differences in the manner in which these cell wall components are targeted and inserted in the expanding portion of tip‐growing cells is reflected by the identification of elements of the plant cell wall synthesis machinery which have been shown to play unique roles in tip‐growing cells. In this review, we summarize our current understanding of the tip growth process, with a particular focus on the subcellular targeting of newly synthesized cell wall components, and their roles in this form of plant cell expansion. image Erik Nielsen (Corresponding author)

Tip growth

Plant cell

Root hair

10.1111/jipb.12077

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Citations (77)

A role for the RabA4b effector protein PI-4Kβ1 in polarized expansion of root hair cells in Arabidopsis thaliana

The Journal of Cell Biology (2006)

Mary L. Preuss Aaron J. Schmitz Julie M. Thole Heather K.S. Bonner Marisa S. Otegui

The RabA4b GTPase labels a novel, trans-Golgi network compartment displaying a developmentally regulated polar distribution in growing Arabidopsis thaliana root hair cells. GTP bound RabA4b selectively recruits the plant phosphatidylinositol 4-OH kinase, PI-4Kβ1, but not members of other PI-4K families. PI-4Kβ1 colocalizes with RabA4b on tip-localized membranes in growing root hairs, and mutant plants in which both the PI-4Kβ1 and -4Kβ2 genes are disrupted display aberrant root hair morphologies. PI-4Kβ1 interacts with RabA4b through a novel homology domain, specific to eukaryotic type IIIβ PI-4Ks, and PI-4Kβ1 also interacts with a Ca2+ sensor, AtCBL1, through its NH2 terminus. We propose that RabA4b recruitment of PI-4Kβ1 results in Ca2+-dependent generation of PI-4P on this compartment, providing a link between Ca2+ and PI-4,5P2–dependent signals during the polarized secretion of cell wall components in tip-growing root hair cells.

Root hair

Compartment (ship)

10.1083/jcb.200508116

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Citations (279)

Faculty Opinions recommendation of Golgi-localized STELLO proteins regulate the assembly and trafficking of cellulose synthase complexes in Arabidopsis.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature (2017)

Erik Nielsen

10.3410/f.726410729.793536393

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