Glenn R Hicks - Academia.edu (original) (raw)

Papers by Glenn R Hicks

The Plant Cell, Dec 23, 2016

The endomembrane system is an interconnected network required to establish signal transduction, c... more The endomembrane system is an interconnected network required to establish signal transduction, cell polarity, and cell shape in response to developmental or environmental stimuli. In the model plant Arabidopsis thaliana, there are numerous markers to visualize polarly localized plasma membrane proteins utilizing endomembrane trafficking. Previous studies have shown that the large ARF-GEF GNOM plays a key role in the establishment of basal (rootward) polarity, whereas the apically (shootward) polarized membrane proteins undergo sorting via different routes. However, the mechanism that maintains apical polarity is largely unknown. Here, we used a chemical genomic approach and identified the compound endosidin 16 (ES16), which perturbed apically localized plasma membrane proteins without affecting basal polarity. We demonstrated that ES16 is an inhibitor for recycling of apical, lateral, and nonpolar plasma membrane proteins as well as biosynthetic secretion, leaving the basal proteins as the only exceptions not subject to ES16 inhibition. Further evidence from pharmaceutical and genetic data revealed that ES16 effects are mediated through the regulation of small GTPase RabA proteins and that RabA GTPases work in concert with the BIG clade ARF-GEF to modulate the nonbasal trafficking. Our results reveal that ES16 defines a distinct pathway for endomembrane sorting routes and is essential for the establishment of cell polarity.

Zenodo (CERN European Organization for Nuclear Research), Nov 29, 2020

Interactions between plant cells and the environment rely on modulation of protein receptors, tra... more Interactions between plant cells and the environment rely on modulation of protein receptors, transporters, channels, and lipids at the plasma membrane (PM) to facilitate intercellular communication, nutrient uptake, environmental sensing, and directional growth. These functions are fine-tuned by cellular pathways maintaining or reducing particular proteins at the PM. Proteins are endocytosed, and their fate is decided between recycling and degradation to modulate localization, abundance, and activity. Selective autophagy is another pathway regulating PM protein accumulation in response to specific conditions or developmental signals. The mechanisms regulating recycling, degradation, and autophagy have been studied extensively, yet we are just now addressing their regulation and coordination. Here, we (1) provide context concerning regulation of protein accumulation, recycling, or degradation by overviewing endomembrane trafficking; (2) discuss pathways regulating recycling and degradation in terms of cellular roles and cargoes; (3) review plant selective autophagy and its physiological significance; (4) focus on two decision-making mechanisms: regulation of recycling versus degradation of PM proteins and coordination between autophagy and vacuolar degradation; and (5) identify future challenges.

Proceedings of the National Academy of Sciences of the United States of America, Jul 14, 2005

For the article ''␣ 1-Adrenoceptor stimulation potentiates L-type Ca 2ϩ current through Ca 2ϩ ͞ca... more For the article ''␣ 1-Adrenoceptor stimulation potentiates L-type Ca 2ϩ current through Ca 2ϩ ͞calmodulindependent PK II (CaMKII) activation in rat ventricular myocytes,''

bioRxiv (Cold Spring Harbor Laboratory), Feb 2, 2021

The phytohormone jasmonoyl-L-isoleucine (JA-Ile) regulates many stress responses and developmenta... more The phytohormone jasmonoyl-L-isoleucine (JA-Ile) regulates many stress responses and developmental processes in plants. A co-receptor complex formed by the F-box protein Coronatine Insensitive 1 (COI1) and a Jasmonate (JA) ZIM-domain (JAZ) repressor perceives the hormone. JA-Ile antagonists are invaluable tools for exploring the role of JA-Ile in specific tissues and developmental stages, and for identifying regulatory processes of the signaling pathway. Using two complementary chemical screens, we identified three compounds that exhibit a robust inhibitory effect on both the hormonemediated COI-JAZ interaction and degradation of JAZ1 and JAZ9 in vivo. One molecule, J4, also restrains specific JAinduced physiological responses in different angiosperm plants, including JA-mediated gene expression, growth inhibition, chlorophyll degradation, and anthocyanin accumulation. Interaction experiments with purified proteins indicate that J4 directly interferes with the formation of the Arabidopsis (Arabidopsis thaliana) COI1-JAZ complex otherwise induced by JA. The antagonistic effect of J4 on COI1-JAZ also occurs in the liverwort Marchantia polymorpha, suggesting the mode of action is conserved in land plants. Besides JA signaling, J4 works as an antagonist of the closely related auxin signaling pathway, preventing Transport Inhibitor Response1/Aux-indole-3-acetic acid interaction and auxin responses in planta, including hormone-mediated degradation of an auxin repressor, gene expression, and gravitropic response. However, J4 does not affect other hormonal pathways. Altogether, our results show that this dual antagonist competes with JA-Ile and auxin, preventing the formation of phylogenetically related receptor complexes. J4 may be a useful tool to dissect both the JA-Ile and auxin pathways in particular tissues and developmental stages since it reversibly inhibits these pathways.

HAL (Le Centre pour la Communication Scientifique Directe), Mar 16, 2009

HAL (Le Centre pour la Communication Scientifique Directe), Jan 29, 2011

I would like to thank Terri Lomax, not only for her normal duties as an advisor, but for providin... more I would like to thank Terri Lomax, not only for her normal duties as an advisor, but for providing real encouragement when times were tough. I've always felt that Terri was on my side, no matter what the situation. I think that we have both grown through our relationship. I would also like to express my gratitude to Dave Ray le. Not only has he been a great lab mate, committee member and source of knowledge, but he is also my my fishing buddy. Boy, do we have tails to tell! Special thanks to my committee members-Carol and Bruce for many helpful discussions. I would also like to express my appreciation to Rye Meeks-Wagner for his willingness to come all the way from Eugene for my committee meetings. Thanks to Tom Wolpert and Dal lice Mills for substituting on short notice. In particular, Tom was extraordinarily helpful during my many efforts at protein purification. Special thanks should go to my labmates Chris Gaiser, Rosie Hopkins, Catherina Coen, Peggy Rice, and Steve Verhey for many helpful discussions and suggestions. Rosie deserves special recognition for keeping the lab in working order (and for keeping Ray le on his toes). On the domestic front, I want to acknowledge my parents, Eiko and William Hicks for instilling in me the importance of education and by setting an example through a life of honest hard work. Last, but not least, I wish to express gratitude and love to my wife, Katherine. She completes me.

Nature Chemical Biology, Apr 22, 2019

Endocytosis mediates the internalization of proteins and lipids at the plasma membrane and plays ... more Endocytosis mediates the internalization of proteins and lipids at the plasma membrane and plays essential roles in plant growth and development. A new small molecule enables manipulation of plant endocytosis in an acute and transient manner.

Plant Journal, May 5, 2022

SUMMARYRoot hairs are single‐cell projections in the root epidermis. The presence of root hairs g... more SUMMARYRoot hairs are single‐cell projections in the root epidermis. The presence of root hairs greatly expands the root surface, which facilitates soil anchorage and the absorption of water and nutrients. Root hairs are also the ideal system to study the mechanism of polar growth. Previous research has identified many important factors that control different stages of root hair development. Using a chemical genetics screen, in this study we report the identification of a steroid molecule, RHP1, which promotes root hair growth at nanomolar concentrations without obvious change of other developmental processes. We further demonstrate that RHP1 specifically affects tip growth with no significant influence on cell fate or planar polarity. We also show that RHP1 promotes root hair tip growth via acting upstream of the RHD6‐RSL4‐dependent transcriptional pathway and ROP GTPase‐guided local signaling. Finally, we demonstrate that RHP1 exhibits a wide range of effects on different plant species in both monocots and dicots. This study of RHP1 will not only help to dissect the mechanism of root hair tip growth, but also provide a new tool to modify root hair growth in different plant species.

Plant Physiology, Sep 5, 2019

Autophagy is a major catabolic process in eukaryotes with a key role in homeostasis, programmed c... more Autophagy is a major catabolic process in eukaryotes with a key role in homeostasis, programmed cell death, and aging. In plants, autophagy is also known to regulate agronomically important traits such as stress resistance, longevity, vegetative biomass, and seed yield. Despite its significance, there is still a shortage of reliable tools modulating plant autophagy. Here, we describe the first robust pipeline for identification of specific plant autophagy-modulating compounds. Our screening protocol comprises four phases: (1) high-throughput screening of chemical compounds in cell cultures of tobacco (Nicotiana tabacum); (2) confirmation of the identified hits in planta using Arabidopsis (Arabidopsis thaliana); (3) further characterization of the effect using conventional molecular biology methods; and (4) verification of chemical specificity on autophagy in planta. The methods detailed here streamline the identification of specific plant autophagy modulators and aid in unraveling the molecular mechanisms of plant autophagy.

HAL (Le Centre pour la Communication Scientifique Directe), Mar 31, 2010

Plant Physiology, Jun 1, 2007

A novel phenyltriazole acetic acid compound (DAS734) produced bleaching of new growth on a variet... more A novel phenyltriazole acetic acid compound (DAS734) produced bleaching of new growth on a variety of dicotyledonous weeds and was a potent inhibitor of Arabidopsis (Arabidopsis thaliana) seedling growth. The phytotoxic effects of DAS734 on Arabidopsis were completely alleviated by addition of adenine to the growth media. A screen of ethylmethanesulfonatemutagenized Arabidopsis seedlings recovered seven lines with resistance levels to DAS734 ranging from 5-to 125-fold. Genetic tests determined that all the resistance mutations were dominant and allelic. One mutation was mapped to an interval on chromosome 4 containing At4g34740, which encodes an isoform of glutamine phosphoribosylamidotransferase (AtGPRAT2), the first enzyme of the purine biosynthetic pathway. Sequencing of At4g34740 from the resistant lines showed that all seven contained mutations producing changes in the encoded polypeptide sequence. Two lines with the highest level of resistance (125-fold) contained the mutation R264K. The wild-type and mutant AtGPRAT2 enzymes were cloned and functionally overexpressed in Escherichia coli. Assays of the recombinant enzyme showed that DAS734 was a potent, slow-binding inhibitor of the wild-type enzyme (I 50 approximately 0.2 mM), whereas the mutant enzyme R264K was not significantly inhibited by 200 mM DAS734. Another GPRAT isoform in Arabidopsis, AtGPRAT3, was also inhibited by DAS734. This combination of chemical, genetic, and biochemical evidence indicates that the phytotoxicity of DAS734 arises from direct inhibition of GPRAT and establishes its utility as a new and specific chemical genetic probe of plant purine biosynthesis. The effects of this novel GPRAT inhibitor are compared to the phenotypes of known AtGPRAT genetic mutants.

Plant Physiology, Apr 1, 1995

Three nuclear localization signals (NLS), including an unusual Mat alpha 2-like NLS from maize (Z... more Three nuclear localization signals (NLS), including an unusual Mat alpha 2-like NLS from maize (Zea mays) R, were found to compete for binding to plant nuclei. In addition, the authentic yeast Mat alpha 2 NLS, which does not function in mammals, was shown to function in plants in vivo. Our results indicate that plants possess a site at the nuclear pore complex that recognizes the three known classes of NLSs.

Plant Physiology, Aug 18, 2006

Although a wide range of structurally diverse small molecules can act as auxins, it is unclear wh... more Although a wide range of structurally diverse small molecules can act as auxins, it is unclear whether all of these compounds act via the same mechanisms that have been characterized for 2,4-dichlorophenoxyacetic acid (2,4-D) and indole-3-acetic acid (IAA). To address this question, we used a novel member of the picolinate class of synthetic auxins that is structurally distinct from 2,4-D to screen for Arabidopsis (Arabidopsis thaliana) mutants that show chemically selective auxin resistance. We identified seven alleles at two distinct genetic loci that conferred significant resistance to picolinate auxins such as picloram, yet had minimal crossresistance to 2,4-D or IAA. Double mutants had the same level and selectivity of resistance as single mutants. The sites of the mutations were identified by positional mapping as At4g11260 and At5g49980. At5g49980 is previously uncharacterized and encodes auxin signaling F-box protein 5, one of five homologs of TIR1 in the Arabidopsis genome. TIR1 is the recognition component of the Skp1-cullin-F-box complex associated with the ubiquitin-proteasome pathway involved in auxin signaling and has recently been shown to be a receptor for IAA and 2,4-D. At4g11260 encodes the tetratricopeptide protein SGT1b that has also been associated with Skp1-cullin-F-box-mediated ubiquitination in auxin signaling and other pathways. Complementation of mutant lines with their corresponding wild-type genes restored picolinate auxin sensitivity. These results show that chemical specificity in auxin signaling can be conferred by upstream components of the auxin response pathway. They also demonstrate the utility of genetic screens using structurally diverse chemistries to uncover novel pathway components.

Current protocols in plant biology, Dec 1, 2017

Target identification remains a challenging step in plant chemical genomics approaches. Drug affi... more Target identification remains a challenging step in plant chemical genomics approaches. Drug affinity responsive target stability (DARTS) represents a straightforward technique to identify small molecules’ protein targets and assist in the characterization of interactions between small molecules and putative targets identified by other methods. When a small molecule interacts with a protein, it has the potential to stabilize the protein's structure, resulting in a reduced susceptibility to protease action. During the DARTS procedure, protein extracts are treated with proteolytic enzymes, and only proteins that bind to the small molecule are protected from proteolysis. DARTS represents a protocol independent of the molecule's mechanism of action or chemical structure. Another advantage of DARTS is that it does not require additional modifications or tagging of the small molecule. The protocols outlined in this article describe in detail the DARTS technique applied to plant proteins and propose several detection procedures according to protein abundance. © 2017 by John Wiley & Sons, Inc.

HAL (Le Centre pour la Communication Scientifique Directe), Jul 17, 2009

Journal of Applied Glycoscience, 2003

The Arabidopsis Book, 2009

This chapter is a revised version of one originally published in The Arabidopsis Book on July 10,... more This chapter is a revised version of one originally published in The Arabidopsis Book on July 10, 2008, with the same title and authors. The original version included text that had previously been published (Blackwell and Zhao, 2003, Plant Physiology 133: 448-455) but did not properly credit that article. This oversight is corrected in this revised version, which includes additional updated material as well.

The ability to trigger secretion of CPY was tested for all compounds shown. Compounds are referre... more The ability to trigger secretion of CPY was tested for all compounds shown. Compounds are referred by the identification numbers assigned by manufacturer.<b>Copyright information:</b>Taken from "Identification of cellular pathways affected by Sortin2, a synthetic compound that affects protein targeting to the vacuole in "http://www.biomedcentral.com/1472-6769/8/1BMC Chemical Biology 2008;8():1-1.Published online 7 Jan 2008PMCID:PMC2265672.

The vacuole is an essential organelle for plant growth and development. It is the location for th... more The vacuole is an essential organelle for plant growth and development. It is the location for the storage of nutrients; such as sugars and proteins; and other metabolic products. Understanding the mechanisms of vacuolar trafficking and molecule transport across the vacuolar membrane is of great importance in understanding basic plant development and cell biology and for crop quality improvement. Proteins play important roles in vacuolar trafficking; such proteins include Rab GTPase signaling proteins; cargo recognition receptors; and SNAREs (Soluble NSF Attachment Protein Receptors) that are involved in membrane fusion. Some vacuole membrane proteins also serve as the transporters or channels for transport across the tonoplast. Less understood but critical are the roles of lipids in vacuolar trafficking. In this review, we will first summarize molecular composition of plant vacuoles and we will then discuss our latest understanding on the role of lipids in plant vacuolar trafficking and a surprising connection to ribosome function through the study of ribosomal mutants.