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    Bary Shelp

    Fertilizer boron (B) and molybdenum (Mo) were provided to contrasting cultivars of subirrigated pot chrysanthemums at approximately 6–100% of current industry standards in an otherwise balanced nutrient solution during vegetative growth,... more
    Fertilizer boron (B) and molybdenum (Mo) were provided to contrasting cultivars of subirrigated pot chrysanthemums at approximately 6–100% of current industry standards in an otherwise balanced nutrient solution during vegetative growth, and then all nutrients were removed during reproductive growth. Two experiments were conducted for each nutrient in a naturally lit greenhouse using a randomized complete block split-plot design. Boron (0.313–5.00 µmol L−1) or Mo (0.031–0.500 µmol L−1) was the main plot, and cultivar was the sub-plot. Petal quilling was observed with leaf-B of 11.3–19.4 mg kg−1 dry mass (DM), whereas Mo deficiency was not observed with leaf-Mo of 1.0–3.7 mg kg−1 DM. Optimized supplies resulted in leaf tissue levels of 48.8–72.5 mg B kg−1 DM and 1.9–4.8 mg Mo kg−1 DM. Boron uptake efficiency was more important than B utilization efficiency in sustaining plant/inflorescence growth with decreasing B supply, whereas Mo uptake and utilization efficiencies appeared to hav...
    Moderate levels of zinc (3.50, 1.75 or 0.875 μmol·L−1 Zn) or copper (0.75, 0.38 or 0.19 μmol·L−1 Cu), in combination with a complete suite of other essential nutrients, were supplied up to flower bud break only, to two cultivars of... more
    Moderate levels of zinc (3.50, 1.75 or 0.875 μmol·L−1 Zn) or copper (0.75, 0.38 or 0.19 μmol·L−1 Cu), in combination with a complete suite of other essential nutrients, were supplied up to flower bud break only, to two cultivars of subirrigated, potted, pinched chrysanthemums. Market-quality plants were produced with sufficient leaf-zinc or leaf-copper even though the delivery of the respective nutrient could be reduced by 75% compared with an industry standard. These results are interpreted as evidence for improved uptake efficiency with decreasing Zn or Cu delivery. Our modified delivery practice could contribute to low-input production of floricultural crops.
    Postharvest deterioration can result in qualitative and quantitative changes in the marketability of horticultural commodities, as well as considerable economic loss to the industry. Low temperature and controlled atmosphere conditions... more
    Postharvest deterioration can result in qualitative and quantitative changes in the marketability of horticultural commodities, as well as considerable economic loss to the industry. Low temperature and controlled atmosphere conditions (low O2 and elevated CO2) are extensively employed to prolong the postharvest life of these commodities. Nevertheless, they may suffer from chilling injury and other physiological disorders, as well as excessive water loss and bacterial/fungal decay. Research on the postharvest physiological, biochemical, and molecular responses of horticultural commodities indicates that low temperature/controlled atmosphere storage is associated with the promotion of γ-aminobutyrate (GABA) pathway activity, with or without the accumulation of GABA, delaying senescence, preserving quality and ameliorating chilling injury. Regardless of whether apple fruits are stored under low temperature/controlled atmosphere conditions or room temperature, elevated endogenous GABA ...
    Polyamines (PAs) are ubiquitous aliphatic amines that play important roles in growth, development, and environmental stress responses in plants. In this study, we report that exogenous application of spermine (Spm) is effective in the... more
    Polyamines (PAs) are ubiquitous aliphatic amines that play important roles in growth, development, and environmental stress responses in plants. In this study, we report that exogenous application of spermine (Spm) is effective in the induction of resistance to gray mold disease, which is caused by the necrotrophic fungal pathogen Botrytis cinerea, on tomato (Solanum lycopersicum), bean (Phaseolus vulgaris), and Arabidopsis thaliana. High throughput transcriptome analysis revealed a priming role for the Spm molecule in the genus Arabidopsis, resulting in strong upregulation of several important defense-associated genes, particularly those involved in systemic-acquired resistance. Microscopic analysis confirmed that Spm application potentiates endogenous defense responses in tomato leaves through the generation of reactive oxygen species and the hypersensitive response, which effectively contained B. cinerea growth within the inoculated area. Moreover, co-application of Spm and salic...
    Academic scientists face an unpredictable path from plant biology research to real-life application. Fundamental studies of γ-aminobutyrate and carotenoid metabolism, control of Botrytis infection, and the uptake and distribution of... more
    Academic scientists face an unpredictable path from plant biology research to real-life application. Fundamental studies of γ-aminobutyrate and carotenoid metabolism, control of Botrytis infection, and the uptake and distribution of mineral nutrients illustrate that most academic research in plant biology could lead to innovative solutions for food, agriculture, and the environment. The time to application depends on various factors such as the fundamental nature of the scientific questions, the development of enabling technologies, the research priorities of funding agencies, the existence of competitive research, the willingness of researchers to become engaged in commercial activities, and ultimately the insight and creativity of the researchers. Applied research is likely to be adopted more rapidly by industry than basic research, so academic scientists engaged in basic research are less likely to participate in science commercialization. It is argued that the merit of Discovery...
    Greenhouse floriculture operations pose significant environmental risk due to extensive inputs of fertilizer, especially nitrogen and phosphorus (P). Recent evidence shows that the use efficiency for nitrogen or sulphur is markedly... more
    Greenhouse floriculture operations pose significant environmental risk due to extensive inputs of fertilizer, especially nitrogen and phosphorus (P). Recent evidence shows that the use efficiency for nitrogen or sulphur is markedly improved in subirrigated potted chrysanthemums (Chrysanthemum morifolium Ramat.) by supplying a moderate level of the nutrient during vegetative growth, and removing the entire nutrient suite at the onset of reproductive growth, without adverse effects on plant quality. Here, two split-plot experiments were conducted with subirrigated, potted, disbudded chrysanthemums grown in a peat:perlite mixture under greenhouse conditions (high- or low-ambient light) with inorganic orthophosphate (Pi) treatment (2.6 mmol L−1 Pi supplied during the vegetative and reproductive stages, and 2.6, 1.95, or 1.3 mmol L−1 Pi supplied during the vegetative stage only) as the main plot and cultivar (‘Olympia’ and ‘Covington’) as the subplot. Market quality plants with sufficien...
    Polyamines represent a potential source of 4-aminobutyrate (GABA) in plants exposed to abiotic stress. Terminal catabolism of putrescine in Arabidopsis thaliana involves amine oxidase and the production of 4-aminobutanal, which is a... more
    Polyamines represent a potential source of 4-aminobutyrate (GABA) in plants exposed to abiotic stress. Terminal catabolism of putrescine in Arabidopsis thaliana involves amine oxidase and the production of 4-aminobutanal, which is a substrate for NAD+-dependent aminoaldehyde dehydrogenase (AMADH). Here, two AMADH homologs were chosen (AtALDH10A8 and AtALDH10A9) as candidates for encoding 4-aminobutanal dehydrogenase activity for GABA synthesis. The two genes were cloned and soluble recombinant proteins were produced in Escherichia coli. The pH optima for activity and catalytic efficiency of recombinant AtALDH10A8 with 3-aminopropanal as substrate was 10.5 and 8.5, respectively, whereas the optima for AtALDH10A9 were approximately 9.5. Maximal activity and catalytic efficiency were obtained with NAD+ and 3-aminopropanal, followed by 4-aminobutanal; negligible activity was obtained with betaine aldehyde. NAD+ reduction was accompanied by the production of GABA and β-alanine, respectiv...
    1-Methylcyclopropene (1-MCP) delays ethylene-meditated ripening of apple (Malus domestica Borkh.) fruit during controlled atmosphere (CA) storage. Here, we tested the hypothesis that 1-MCP and CA storage enhances the levels of polyamines... more
    1-Methylcyclopropene (1-MCP) delays ethylene-meditated ripening of apple (Malus domestica Borkh.) fruit during controlled atmosphere (CA) storage. Here, we tested the hypothesis that 1-MCP and CA storage enhances the levels of polyamines (PAs) and 4-aminobutyrate (GABA) in apple fruit. A 46-week experiment was conducted with "Empire" apple using a split-plot design with four treatment replicates and 3°C, 2.5 kPa O2, and 0.03 or 2.5 kPa CO2 with or without 1 μL L(-1) 1-MCP. Total PA levels were not elevated by the 1-MCP treatment. Examination of the individual PAs revealed that: (i) total putrescine levels tended to be lower with 1-MCP regardless of the CO2 level, and while this was mostly at the expense of free putrescine, large transient increases in soluble conjugated putrescine were also evident; (ii) total spermidine levels tended to be lower with 1-MCP, particularly at 2.5 kPa CO2, and this was mostly at the expense of soluble conjugated spermidine; (iii) total spermi...
    Background The ubiquitous, non-proteinaceous amino acid GABA (γ-aminobutyrate) accumulates in plants subjected to abiotic stresses such as chilling, O2 deficiency and elevated CO2. Recent evidence indicates that controlled atmosphere... more
    Background The ubiquitous, non-proteinaceous amino acid GABA (γ-aminobutyrate) accumulates in plants subjected to abiotic stresses such as chilling, O2 deficiency and elevated CO2. Recent evidence indicates that controlled atmosphere storage causes the accumulation of GABA in apple (Malus x domestica Borkh.) fruit, and now there is increasing interest in the biochemical mechanisms responsible for this phenomenon. Here, we investigated whether this phenomenon could be mediated via Ca2+/calmodulin (CaM) activation of glutamate decarboxylase (GAD) activity. Results GAD activity in cell-free extracts of apple fruit was stimulated by Ca2+/CaM at physiological pH, but not at the acidic pH optimum. Based on bioinformatics analysis of the apple genome, three apple GAD genes were identified and their expression determined in various apple organs, including fruit. Like recombinant Arabidopsis GAD1, the activity and spectral properties of recombinant MdGAD1 and MdGAD2 were regulated by Ca2+/Ca...
    Subirrigation systems are popular for reducing nutrient usage in indoor floricultural production. Two open subirrigation experiments were conducted in a commercial setting using multiple chrysanthemum cultivars and up to 75% less N–P–K... more
    Subirrigation systems are popular for reducing nutrient usage in indoor floricultural production. Two open subirrigation experiments were conducted in a commercial setting using multiple chrysanthemum cultivars and up to 75% less N–P–K than industry standards. The lowest N–P–K levels supplied in the nutrient solution (in mmol·L−1: 5.4 N, 0.71−0.97 P, 1.9−4.1 K) up to bud break, were associated with acceptable leaf N–P–K levels [4.5−5.4% dry matter (DM), 0.23−0.60% DM, and 3.3−5.6% DM, respectively]. These findings validate our modified delivery practice and the use of lower N–P–K inputs in the production of subirrigated pot chrysanthemums.
    Industry standards for nutrient delivery to greenhouse-grown ornamentals are typically in excess of the plant’s needs and can be reduced without causing adverse effects. Previous studies have reduced the level of specific nutrients or... more
    Industry standards for nutrient delivery to greenhouse-grown ornamentals are typically in excess of the plant’s needs and can be reduced without causing adverse effects. Previous studies have reduced the level of specific nutrients or suite of nutrients over the entire crop cycle or at the onset of reproductive growth. Here, two split-plot experiments (four blocks each) were conducted with subirrigated, potted, disbudded chrysanthemums (Chrysanthemum morifolium Ramat.) grown under greenhouse conditions with sulphate treatment (2.25 mmol L−1 S supplied continuously over the crop cycle in experiment 2 only and 2.25, 1.125, or 0.5625 mmol L−1 S interrupted at inflorescence emergence) as the main plot and cultivar (‘Olympia’ and ‘Covington’) as the sub-plot. Morphological characteristics of plants with fully-expanded inflorescences were unaffected by decreasing S delivery over the crop cycle. Dry mass (DM) yields and S budgets revealed that supply-based S use and S uptake efficiencies i...
    g-Aminobutyric acid transaminase (GABA-T) catalyses the breakdown of GABA to succinic semialdehyde. In this report, three GABA-T isoforms were identified in the tomato (Solanum lycopersicum L.) plant. The deduced amino acid sequences of... more
    g-Aminobutyric acid transaminase (GABA-T) catalyses the breakdown of GABA to succinic semialdehyde. In this report, three GABA-T isoforms were identified in the tomato (Solanum lycopersicum L.) plant. The deduced amino acid sequences of the three isoforms are highly similar over most of their coding regions with the exception of their N-terminal regions. Transient expression of the individual full-length GABA-T isoforms
    The authors describe the development of gamma aminobutyrate (GABA) as a potential control agent in plant – invertebrate pest systems. The evidence indicates that GABA accumulation in plants in response to biotic and abiotic stresses is... more
    The authors describe the development of gamma aminobutyrate (GABA) as a potential control agent in plant – invertebrate pest systems. The evidence indicates that GABA accumulation in plants in response to biotic and abiotic stresses is mediated via the activation of glutamate decarboxylase. More applied research, based on the fact that GABA acts as an inhibitory neurotransmitter in invertebrate pests, indicates that ingested GABA disrupts nerve functioning and causes damage to oblique-banded leafroller larvae, and that walking or herbivory by tobacco budworm and oblique-banded leafroller larvae stimulate GABA accumulation in soybean and tobacco, respectively. In addition, elevated levels of endogenous GABA in genetically engineered tobacco deter feeding by tobacco budworm larvae and infestation by the northern root-knot nematode. It is concluded that genetically engineered crop species overexpressing glutamate decarboxylase and having high GABA-producing potential may be an alternat...
    ... Proc Natl Acad Sci USA 103 : 7460 – 7464 Cholewa E , Cholewinski AJ , Shelp BJ , Snedden WA , Bown AW (1997) Cold shock-stimulated g ... Plant Physiol 99 : 659 – 664 Cramer GR , Ergül A , Grimplet J , Tillett RL , Tattersall EAR ,... more
    ... Proc Natl Acad Sci USA 103 : 7460 – 7464 Cholewa E , Cholewinski AJ , Shelp BJ , Snedden WA , Bown AW (1997) Cold shock-stimulated g ... Plant Physiol 99 : 659 – 664 Cramer GR , Ergül A , Grimplet J , Tillett RL , Tattersall EAR , Bohlman MC , Vincent D , Sonderegger J ...
    Molecular modelling suggests that a group of proteins in plants known as the β-hydroxyacid dehydrogenases, or the hydroxyisobutyrate dehydrogenase superfamily, includes enzymes that reduce succinic semialdehyde and glyoxylate to... more
    Molecular modelling suggests that a group of proteins in plants known as the β-hydroxyacid dehydrogenases, or the hydroxyisobutyrate dehydrogenase superfamily, includes enzymes that reduce succinic semialdehyde and glyoxylate to γ-hydroxybutyrate and glycolate respectively. Recent biochemical and expression studies reveal that NADPH-dependent cytosolic (termed GLYR1) and plastidial (termed GLYR2) isoforms of succinic semialdehyde/glyoxylate reductase exist in Arabidopsis. Succinic semialdehyde and glyoxylate are typically generated in leaves via two distinct metabolic pathways, γ-aminobutyrate and glycolate respectively. In the present review, it is proposed that the GLYRs function in the detoxification of both aldehydes during stress and contribute to redox balance. Outstanding questions are highlighted in a scheme for the subcellular organization of the detoxification mechanism in Arabidopsis.
    Moderate levels of calcium or magnesium were applied to two cultivars of subirrigated, potted, pinched chrysanthemums during vegetative growth only. Market-quality plants were produced with sufficient leaf-calcium or leaf-magnesium even... more
    Moderate levels of calcium or magnesium were applied to two cultivars of subirrigated, potted, pinched chrysanthemums during vegetative growth only. Market-quality plants were produced with sufficient leaf-calcium or leaf-magnesium even though the delivery of the respective nutrient could be reduced by approximately 87.5%, compared to industry standards. This practice could contribute to low-input production of floricultural crops.
    Plant NADPH-dependent glyoxylate/succinic semialdehyde reductases 1 and 2 (GLYR1 and GLYR2) are considered to be involved in detoxifying harmful aldehydes, thereby preserving plant health during exposure to various abiotic stresses.... more
    Plant NADPH-dependent glyoxylate/succinic semialdehyde reductases 1 and 2 (GLYR1 and GLYR2) are considered to be involved in detoxifying harmful aldehydes, thereby preserving plant health during exposure to various abiotic stresses. Phylogenetic analysis revealed that the two GLYR isoforms appeared in the plant lineage prior to the divergence of the Chlorophyta and Streptophyta, which occurred approximately 750 million years ago. Green fluorescent protein fusions of apple (Malus x domestica Borkh.), rice (Oryza sativa L.) and Arabidopsis thaliana [L.] Heynh GLYRs were transiently expressed in tobacco (Nicotiana tabaccum L.) suspension cells or Arabidopsis protoplasts, as well in methoxyfenozide-induced, stably transformed Arabidopsis seedlings. The localization of apple GLYR1 confirmed that this isoform is cytosolic, whereas apple, rice and Arabidopsis GLYR2s were localized to both mitochondria and plastids. These findings highlight the potential involvement of GLYRs within distinct...
    Gamma-aminobutyrate (GABA) is a ubiquitous four-carbon, non-protein amino acid. In plants, stress-induced GABA accumulation is well documented. However, the role(s) of GABA accumulation is contentious. In this Opinion article, we argue... more
    Gamma-aminobutyrate (GABA) is a ubiquitous four-carbon, non-protein amino acid. In plants, stress-induced GABA accumulation is well documented. However, the role(s) of GABA accumulation is contentious. In this Opinion article, we argue that wounding due to herbivory and crawling by insect larvae causes rapid GABA accumulation via the disruption of cellular compartmentation and the release of the acidic vacuolar contents to the cytosol. The activity of glutamate decarboxylase, the cytosolic enzyme responsible for GABA synthesis, has an acidic pH optimum. Subsequent GABA ingestion has a plant defense function by directly acting on GABA-regulated invertebrate neuromuscular junctions. Plants with an enhanced GABA-producing capacity reduce herbivory by invertebrate pests. These findings suggest that GABA accumulation is a rapidly deployed, local resistance mechanism that constitutes a first line of defense in deterring herbivory.
    Soybean cyst nematode (Heterodera glycines Ichinohe; SCN) is the primary disease responsible for yield loss of soybean [Glycine max (L.) Merr.]. Resistant cultivars are an effective management tool; however, the sources currently... more
    Soybean cyst nematode (Heterodera glycines Ichinohe; SCN) is the primary disease responsible for yield loss of soybean [Glycine max (L.) Merr.]. Resistant cultivars are an effective management tool; however, the sources currently available have common resistant genes. Glycine soja Sieb. and Zucc., the wild ancestor of domesticated soybean, represents a diverse germplasm pool with known SCN resistance. The objectives of this research were to: (1) determine the genetic variation and inheritance of SCN resistance in a G. max ('S08-80') x G. soja (PI464925B) F (4:5) recombinant inbred line (RIL) population; and (2) identify and evaluate quantitative trait loci (QTL) associated with SCN resistance. Transgressive segregation for resistance was observed, although neither parent was resistant to the Chatham and Ruthven SCN isolates. Broad sense heritability was 0.81 for the Ruthven and 0.91 for the Chatham isolate. Root dry weight was a significant covariate that influenced cyst counts. One RIL [female index (FI) = 5.2 +/- 1.11] was identified as resistant to the Chatham isolate (FI < 10). Seventeen and three RILs infected with Chatham and Ruthven isolates, respectively, had mean adjusted cyst counts of zero. Unique and novel QTL, which derived resistance from G. soja, were identified on linkage groups I, K, and O, and individually explained 8, 7 and 5% (LOD = 2.1-2.7) of the total phenotypic variation, respectively. Significant epistatic interactions were found between pairs of SSR markers that individually may or may not have been associated with SCN resistance, which explained between 10 and 15% of the total phenotypic variation. Best-fit regression models explained 21 and 31% of the total phenotypic variation in the RIL population to the Chatham and Ruthven isolates, respectively. The results of this study help to improve the understanding of the genetic control of SCN resistance in soybean caused by minor genes resulting in horizontal resistance. The incorporation of the novel resistance QTL from G. soja could increase the durability of SCN-resistance in soybean cultivars, especially if major gene resistance breaks down.
    ... reserved Gaba shunt in developing soybean seeds is associated with hypoxia Barry J. Shelp, Craig S. Walton, Wayne A. Snedden, Lucie G. Tuin, Ivan J. Oresnik and David B. Layzell Shelp, BJ.,... more
    ... reserved Gaba shunt in developing soybean seeds is associated with hypoxia Barry J. Shelp, Craig S. Walton, Wayne A. Snedden, Lucie G. Tuin, Ivan J. Oresnik and David B. Layzell Shelp, BJ., Walton.CS.Snedden,WA.Tuin.LG,Oresnik,IJandLayzell.DB 1995. ...
    Soybean cyst nematode (SCN) is the primary pest responsible for yield losses of Glycine max. Management of SCN remains difficult in commercial soybean production due to the length of its biological cycle, frequent changes in population... more
    Soybean cyst nematode (SCN) is the primary pest responsible for yield losses of Glycine max. Management of SCN remains difficult in commercial soybean production due to the length of its biological cycle, frequent changes in population virulence, and ease of spread via infested soil. Effective management relies on crop rotation in combination with resistant cultivars, which have been derived from a limited germplasm base. Breeding for SCN resistance in soybean is difficult due to the quantitative nature of the trait, genetic variation within SCN populations, time required for phenotyping experimental soybean lines, and environmental factors affecting SCN reproduction. Quantitative trait loci associated with SCN resistance have been identified on 17 of the 20 soybean linkage groups, explaining 1–91% of the total phenotypic variation. Two major resistance genes, rhg 1 and Rhg 4, have been identified on linkage groups G and A2, respectively. Several minor resistance genes have been ide...
    Global climate change and associated adverse abiotic and biotic stress conditions affect plant growth and development, and agricultural sustainability in general. Abiotic and biotic stresses reduce respiration and associated energy... more
    Global climate change and associated adverse abiotic and biotic stress conditions affect plant growth and development, and agricultural sustainability in general. Abiotic and biotic stresses reduce respiration and associated energy generation in mitochondria, resulting in the elevated production of reactive oxygen species (ROS), which are employed to transmit cellular signaling information in response to the changing conditions. Excessive ROS accumulation can contribute to cell damage and death. Production of the non-protein amino acid γ-aminobutyrate (GABA) is also stimulated, resulting in partial restoration of respiratory processes and energy production. Accumulated GABA can bind directly to the aluminum-activated malate transporter and the guard cell outward rectifying K+ channel, thereby improving drought and hypoxia tolerance, respectively. Genetic manipulation of GABA metabolism and receptors, respectively, reveal positive relationships between GABA levels and abiotic/biotic ...
    Enzymes that reduce the aldehyde chemical grouping (i.e. H-C¼O) to its corresponding alcohol could be crucial in maintaining plant health. Recently, recombi- nant expression of a cytosolic enzyme from Arabidop- sis thaliana (L.) Heynh... more
    Enzymes that reduce the aldehyde chemical grouping (i.e. H-C¼O) to its corresponding alcohol could be crucial in maintaining plant health. Recently, recombi- nant expression of a cytosolic enzyme from Arabidop- sis thaliana (L.) Heynh (designated as glyoxylate reductase 1 or AtGR1) revealed that it effectively catalyses the in vitro reduction of both glyoxylate and succinic semialdehyde (SSA). In this paper,
    Enzymes that reduce the aldehyde chemical grouping (i.e. H-C¼O) to its corresponding alcohol could be crucial in maintaining plant health. Recently, recombi- nant expression of a cytosolic enzyme from Arabidop- sis thaliana (L.) Heynh... more
    Enzymes that reduce the aldehyde chemical grouping (i.e. H-C¼O) to its corresponding alcohol could be crucial in maintaining plant health. Recently, recombi- nant expression of a cytosolic enzyme from Arabidop- sis thaliana (L.) Heynh (designated as glyoxylate reductase 1 or AtGR1) revealed that it effectively catalyses the in vitro reduction of both glyoxylate and succinic semialdehyde (SSA). In this paper,
    Glutamate decarboxylase (GAD, EC 4.1.1.15) catalyses the a- decarboxylation of glutamate to produce g-aminobutyrate (GABA). The nucleotide sequences of two divergent GADs (designated GAD1 and GAD3) were isolated from a Nicotiana tabacum... more
    Glutamate decarboxylase (GAD, EC 4.1.1.15) catalyses the a- decarboxylation of glutamate to produce g-aminobutyrate (GABA). The nucleotide sequences of two divergent GADs (designated GAD1 and GAD3) were isolated from a Nicotiana tabacum L. cv. Samsun NN leaf cDNA library. Open reading frames indicated that GAD1 encodes a polypeptide of 496 amino acids and has greater than 99% identity with known