Valerie Mary Sponsel
@utsa.edu
Professor and Distinguished Teaching Professor, Department of Integrative Biology
The University of Texas at San Antonio
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Kaitlyn Varela, Hadi D. Arman, Mitchel S. Berger, Valerie M. Sponsel, Chin-Hsing Annie Lin, and Francis K. Yoshimoto
American Chemical Society (ACS)
Artemisia annua is the plant that produces artemisinin, an endoperoxide-containing sesquiterpenoid used for the treatment of malaria. A. annua extracts, which contain other bioactive compounds, have been used to treat other diseases, including cancer and COVID-19, the disease caused by the virus SARS-CoV-2. In this study, a methyl ester derivative of arteannuin B was isolated when A. annua leaves were extracted with a 1:1 mixture of methanol and dichloromethane. This methyl ester was thought to be formed from the reaction between arteannuin B and the extracting solvent, which was supported by the fact that arteannuin B underwent 1,2-addition when it was dissolved in deuteromethanol. In contrast, in the presence of N-acetylcysteine methyl ester, a 1,4-addition (thiol-Michael reaction) occurred. Arteannuin B hindered the activity of the SARS CoV-2 main protease (nonstructural protein 5, NSP5), a cysteine protease, through time-dependent inhibition. The active site cysteine residue of NSP5 (cysteine-145) formed a covalent bond with arteannuin B as determined by mass spectrometry. In order to determine whether cysteine adduction by arteannuin B can inhibit the development of cancer cells, similar experiments were performed with caspase-8, the cysteine protease enzyme overexpressed in glioblastoma. Time-dependent inhibition and cysteine adduction assays suggested arteannuin B inhibits caspase-8 and adducts to the active site cysteine residue (cysteine-360), respectively. Overall, these results enhance our understanding of how A. annua possesses antiviral and cytotoxic activities.
Valerie M. Sponsel
John Wiley & Sons, Ltd
Chapter 1 briefly recounts the discovery of gibberellins (GAs) as natural products of the fungus Gibberella fujikuroi in the early part of the twentieth century, and provides a historical overview of GA research from the late 1950s to the present day. It describes howbiosynthetic pathways toGAs inGibberella and higher plants were defined, and how stem length mutants of cereals and legumes were instrumental in establishing which GAs are biologically active and have hormonal function. The chapter presents an overview of the cereal aleurone system in which GA signalling was first studied, and describes how more recent use of Arabidopsis and rice led to the characterisation of a GA receptor (GID1) and downstream regulatory proteins (DELLAs). A number of DELLA-interacting proteins are described, illustrating how it is that GA-induced degradation of DELLAs facilitates downstream responses including cell elongation. Other ‘classical’ GA responses include germination and flowering in some species.
Mohsen Qasemi, Drew W. Johnson, and Valerie M. Sponsel
Wiley
A new method is explored for subsurface irrigation where the plant root structure is used as the subsurface water distribution system. Plants are severed at the stem and the stem stump is attached to a pressurized water source such that water may permeate into surrounding soil through the existing buried root system. This pressurized root system serves as a well‐ distributed buried irrigation water source to the other nearby growing plants taking up water. The feasibility of using an existing root structure in this manner to supply water at rates necessary to satisfy other growing plants was determined by conducting laboratory water hydraulic conductance studies. Laboratory growth studies were used to directly test the proposed root templated irrigation (RTI) approach. Modelling simulations were also utilized to extend laboratory findings to other scenarios and compare expected water use efficiency benefits associated with this proposed irrigation method with surface irrigation (SI) and subsurface drip irrigation (SDI) practices. Irrigation study measurements showed that RTI provides more efficient water use as compared to SI. Modelling calculations were in qualitative agreement with the experimental studies, indicating that RTI yields improvement in root water uptake over the SI and also SDI unless SDI source spacing is narrow. Copyright © 2016 John Wiley & Sons, Ltd.
Peter Hedden and Valerie Sponsel
Springer Science and Business Media LLC
Valerie Sponsel
Elsevier BV
Miguelangel Sauceda, Drew W. Johnson, Jie Huang, Sazzad Bin-Shafique, Valerie M. Sponsel, and Mark Appleford
American Society of Civil Engineers (ASCE)
AbstractThis research investigates the use of polymer-infused roots for soil-improvement applications. By infusing polymer through the easily accessible above-surface plant stems, polymer-infused roots can be created without subsurface excavations. Evaluation of this technique involves identifying the improvements from polymer-infused roots by measuring in situ shear strength of soil using a vane shear apparatus and by measuring the tensile strength using split-tension tests in the laboratory. Roots of Ruellia squarrosa and Artemisia annua plants were infused with a mixture of epoxy resin and polyoxyalkylamine blend hardener. Compared with noninfused roots, polymer-infused roots provided an additional 22 kPa (28%) of shear strength for elastic silt and an additional 13.1 kPa (25%) of shear strength for low-plasticity clay with a corresponding 13.6-kPa (55%) increase in tensile strength for the low-plasticity clay. Acid hydrolysis testing was performed to ascertain the potential durability of the polymer-i...
Miguelangel Sauceda, Drew W. Johnson, Jie Huang, Sazzad Bin-Shafique, Valerie M. Sponsel, and Mark Appleford
American Society of Civil Engineers (ASCE)
AbstractPolymer-infused plant roots can be created without soil excavation by infusing polymer into the roots of plants through the easily accessible above-surface plant stems. Efficacy of this technique for use in soil stabilization applications involves assessing the durability of polymer-infused plant roots. Polymer content was determined for infused Artemisia annua plant roots. Durability of these polymer-infused roots was evaluated by mass loss resistance and strength loss resistance of acid-treated samples. Durability in the context of soil stabilization applications was determined by comparing the shear strength of aged samples. Polymer infusions improved the durability of the plant material. Infused plant stems incubated in acid for 15 weeks lost 29% mass, whereas noninfused stems lost 60% mass. Infused roots incubated in acid for 24 h retained a tensile strength of 25 MPa, whereas noninfused acid-treated roots had a tensile strength of 12 MPa. In comparison to plant roots that provided no enhance...
Karl W Eisenacher, Drew W Johnson, Mark Appleford, and Valerie M Sponsel
SAGE Publications
By infusing a thermoset epoxy polymer into the root system of a plant, we aim to create an in situ plant-polymer composite material of high tensile strength resistant to biodegradation and suitable for soil stabilization applications. Microscopy imaging, volume and mass measurements, thermogravimetric analysis, and tensile testing were conducted to characterize the effects of infusing polymer into the plant system. The polymer appears to travel predominantly through xylem vessels of the plant system during infusions. Maximum tensile strength and modulus of elasticity are increased by 107% and 92%, respectively, with a polymer content of 59% by mass after infusions were conducted.
Jianhua Ruan, Joseph Perez, Brian Hernandez, Chengwei Lei, Garry Sunter, and Valerie M Sponsel
Springer Science and Business Media LLC
Valerie M. Sponsel and Peter Hedden
Springer Netherlands
D. González, Q. Zhao, C. McMahan, D. Velasquez, W. E. Haskins, V. Sponsel, A. Cassill, and R. Renthal
Wiley
Some chemosensory proteins (CSPs) are expressed in insect sensory appendages and are thought to be involved in chemical signalling by ants. We identified 14 unique CSP sequences in expressed sequence tag (EST) libraries of the red imported fire ant, Solenopsis invicta. One member of this group (Si‐CSP1) is highly expressed in worker antennae, suggesting an olfactory function. A shotgun proteomic analysis of antennal proteins confirmed the high level of Si‐CSP1 expression, and also showed expression of another CSP and two odorant‐binding proteins (OBPs). We cloned and expressed the coding sequence for Si‐CSP1. We used cyclodextrins as solubilizers to investigate ligand binding. Fire ant cuticular lipids strongly inhibited Si‐CSP1 binding to the fluorescent dye N‐phenyl‐naphthylamine, suggesting cuticular substances are ligands for Si‐CSP1. Analysis of the cuticular lipids showed that the endogenous ligands of Si‐CSP1 are not cuticular hydrocarbons.
Isabel Desgagné-Penix and Valerie M. Sponsel
Oxford University Press (OUP)
Bioactive gibberellins (GAs) affect many biological processes including germination, stem growth, transition to flowering, and fruit development. The location, timing, and level of bioactive GA are finely tuned to ensure that optimal growth and development occur. The balance between GA biosynthesis and deactivation is controlled by external factors such as light and by internal factors that include auxin. The role of auxin transport inhibitors (ATIs) and auxins on GA homeostasis in intact light-grown Arabidopsis thaliana (L.) Heynh. seedlings was investigated. Two ATIs, 1-N-naphthylthalamic acid (NPA) and 1-naphthoxyacetic acid (NOA) caused elevated expression of the GA biosynthetic enzyme AtGA20-oxidase1 (AtGA20ox1) in shoot but not in root tissues, and only at certain developmental stages. It was investigated whether enhanced AtGA20ox1 gene expression was a consequence of altered flow through the GA biosynthetic pathway, or was due to impaired GA signalling that can lead to enhanced AtGA20ox1 expression and accumulation of a DELLA protein, Repressor of ga1-3 (RGA). Both ATIs promoted accumulation of GFP-fused RGA in shoots and roots, and this increase was counteracted by the application of GA4. These results suggest that in ATI-treated seedlings the impediment to DELLA protein degradation may be a deficiency of bioactive GA at sites of GA response. It is proposed that the four different levels of AtGA20ox1 regulation observed here are imposed in a strict hierarchy: spatial (organ-, tissue-, cell-specific) > developmental > metabolic > auxin regulation. Thus results show that, in intact auxin- and auxin transport inhibitor-treated light-grown Arabidopsis seedlings, three other levels of regulation supersede the effects of auxin on AtGA20ox1.
Isabel Desgagné-Penix, Suntara Eakanunkul, Jeremy P. Coles, Andrew L. Phillips, Peter Hedden, and Valerie M. Sponsel
Wiley
The Arabidopsis gene BIG (formerly DOC1/TIR3/UMB1/ASA1) is known to encode a huge calossin-like protein that is required for polar auxin transport (PAT). Mutations at this locus, in addition to reducing PAT, can alter the sensitivity of plants to several hormones and light. The tir3-1 allele of BIG reduces the response of plants to application of the gibberellin (GA) precursors ent-kaurenoic acid and GA12 and its semidwarf phenotype is partially reversed by C19-GAs. The effects of auxin transport inhibitors (ATIs) on GA 20-oxidation was examined in wild-type and tir3-1 seedlings. 1-N-naphthylphthalamic acid (NPA) and triiodobenzoic acid lead to overexpression of the GA-biosynthetic gene AtGA20ox1 comparable in magnitude to the overexpression observed in seedlings treated with paclobutrazol, a GA biosynthesis inhibitor. In contrast to that of AtGA20ox1, overexpression of AtGA20ox2 is pronounced only in paclobutrazol-treated Col and Ler, and is less in tir3-1 and in all NPA-treated seedlings. Thus the effects of BIG and ATIs on the expression of genes encoding GA 20-oxidases are complex, and suggest that at least in some tissues ATIs, directly or indirectly, may reduce the level of bioactive GA and/or alter GA signal transduction.
Valerie M. Sponsel
Springer Science and Business Media LLC
Valerie M. Sponsel
Springer Science and Business Media LLC
V. M. Sponsel, F. W. Schmidt, S. G. Porter, M. Nakayama, S. Kohlstruk, and M. Estelle
Oxford University Press (OUP)
Abstract Chemical mutagenesis of Arabidopsis thaliana (L.) Heynh. yielded four semidwarf mutants, all of which appeared to be gibberellin (GA)-biosynthesis mutants. All four had atypical response profiles to C20-GAs, suggesting that each had impaired 20-oxidation. One mutant, 11.2, was shown to be allelic to ga5 and has been named ga5–2. It had altered metabolism of [14C]GA15 relative to that in wild-type plants and undetectable levels of C19-GAs in young stems, consistent with the known function of GA5 as a stem-expressed GA 20-oxidase. Two mutants (2.1 and 10.3), which had very short inflorescences and siliques, were allelic to each other but not to the known GA-responding mutants, ga1 to ga5. The locus defined by these two mutations is provisionally named GA6 and is purported to encode an inflorescence- and silique-expressed GA 20-oxidase. A double mutant, ga5–2 ga6–2, had an extreme dwarf phenotype with very short siliques. The fourth mutation, 1.1, gave a phenotype like ga5, but was not allelic to any of the known ga mutations. It has not yet been given a gene symbol pending further studies.
V. M. Sponsel, J. J. Ross, M. R. Reynolds, G. M. Symons, and J. B. Reid
Oxford University Press (OUP)
Abstract Dark-grown seedlings of the lip1 (light independent photomorphogenesis) mutant of Pisum sativum L. display many features of de-etiolated growth and are similar in many respects to wild-type (WT) seedlings grown in the light. The involvement of gibberellins (GAs) with the mutant phenotype was examined by applying GA1 and GA20 to the mutant and WT, and by quantifying endogenous GA1, GA8, GA19, GA20, and GA29 levels in the two genotypes. These experiments were conducted in both the light and the dark. In neither environment could GA application restore elongation in the mutant to that in GA-treated WT plants. Quantification of GAs provided further evidence that the mutant phenotype is not attributable to a deficiency in endogenous GA1. However, dark-grown lip1 seedlings contained lower levels of GA19 and higher levels of GA20 than dark-grown WT plants, whereas in the light, the effect of the mutation on the ratio of GA19 to GA20 was reversed. Thus, there appears to be a complex interaction between the lip1 mutation, the light regime, and the step GA19 to GA20.
Michael H. Beale and Valerie M. Sponsel
Springer Science and Business Media LLC
C. M. Santes, P. Hedden, V. M. Sponsel, J. B. Reid, and J. L. Garcia-Martinez
Oxford University Press (OUP)
The effect of the le mutation on the growth and gibberellin (GA) content of developing fruits was investigated using the near-isogenic lines of Pisum sativum L. 205+ (LeLe) and 205- (lele). Although stem elongation is known to be reduced in 205- plants by approximately 65%, the growth of pods and seeds was unaffected by the le mutation. GA1, GA3, and GA20 stimulated parthenocarpic development of unpollinated ovaries on both 205+ and 205- plants. GA20 was less active on 205- ovaries than on 205+, whereas GA1 had similar, high activity in both lines. The activity of GA3 was even higher than that of GA1 in both lines. Decapitation of 205+ plants induced parthenocarpic development of unpollinated ovaries, but this treatment was much less effective on 205- plants. The contents of GA1 and GA8 in entire ovaries 6 d after anthesis, as well as in the pod and fertilized ovules, were substantially lower in 205- than in 205+ plants, whereas the reverse was true for the levels of GA20 and GA29. These results suggest that 3[beta]-hydroxylation of GA20 to GA1 is reduced in ovaries as well as in vegetative tissues. Thus, the le mutation appears to be expressed in young reproductive organs of the 205- line, even though it does not affect the fruit phenotype. Because the content of GA3 in the ovary was similar in the two lines, one explanation for the normal fruit size in the 205- line is that GA3 is the native regulator of pod growth. Alternatively, sufficient GA1 may still be produced in 205- fruits to maintain normal pod growth.
Valerie M. Sponsel and James B. Reid
Oxford University Press (OUP)
Dwarf (le(5839)) seedlings of Pisum sativum respond to gibberellin A(20) (GA(20)) in the dark, although the same dosage of GA(20) applied to light-grown le(5839) seedlings elicits no growth response. The acylcyclohexanedione growth retardant, LAB 198 999, which is known to inhibit gibberellin oxidation and in particular 3beta-hydroxylation such as the conversion of GA(20) to GA(1), also inhibits the growth response of dark-grown dwarf (le(5839)) seedlings to GA(20). Thus, the biological activity of GA(20) in the dark appears to be a consequence of its conversion to GA(1), even though it is known from studies with light-grown seedlings that the le mutation reduces the conversion of GA(20) to GA(1).
V.A. Smith, V.M. Sponsel, C. Knatt, P. Gaskin, and J. MacMillan
Springer Science and Business Media LLC
Gillian M. Boolher, Michael D. Gale, Paul Gaskin, Jake MacMiilan, and Valerie M. Sponsel
Wiley
The gibberellin (GA) content of barley (Hordeum vulgare L.) cv. Triumph was analysed by full scan gas chromatography-mass spectrometry. Developing grain contained several di-, tri-, and tetra-hydroxylated GAs, with the most abundant ones being hydroxylated at C-2, C-3, C-12β, and/or C-18. In contrast, the only GAs to be detected in shoots of 9-day old dark- and light-grown seedlings of Triumph were 13-hydroxylated C19-GAs, namely GA1, GA8, GA20, and GA29, (all of which are components of the early 13-hydroxylation GA biosynthetic pathway) and GA3. Feeds of [13C.3H2GA20, confirmed that GA20 is a precursor of GA1, GA8, and GA29 in barley shoots. From these results it is suggested that stem growth of barley, in common with that of several other mono- and dicotyledons, is controlled by GA,. Homozygous gal and gal lines were obtained after backcrossing to Triumph. These were then compared to Triumph with respect to their GA content and response to applied GAs and GA precursors. Shoots of the homozygous gal gal plants contained ca 6-fold less GA1, than Triumph. These plants responded to all ent-kaurenoids and 13-hydroxylated C20- and C19-GAs tested. It is concluded that the gal locus impairs the GA biosynthetic pathway prior to ent-kaurene, most probably at ent-kaurene synthetase. In contrast, shoots of homozygous gal gal line contained ca 10-fold higher levels of GA, than Triumph, but failed to respond to applied GA, or GA3. The gal locus therefore confers insensitivity to both exogenous and endogenous GAs, possibly by perturbing the reception or transduction of the GA1 signal.
J. L. Garcia-Martinez, V. M. Sponsel, and P. Gaskin
Springer Science and Business Media LLC
V. M. Sponsel
Springer Science and Business Media LLC