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Publications - Molecular Signal Processing

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Displaying results 31 to 40 of 56.

Publications

Levy, M.; Wang, Q.; Kaspi, R.; Parrella, M.P.; Abel, S. Arabidopsis IQD1, a novel calmodulin-binding nuclear protein, stimulates glucosinolate accumulation and plant defense Plant Journal 43, 79 - 96, (2005) DOI: 10.1111/j.1365-313X.2005.02435.x

Glucosinolates are a class of secondary metabolites with important roles in plant defense and human nutrition. To uncover regulatory mechanisms of glucosinolate production, we screened Arabidopsis thaliana T-DNA activation-tagged lines and identified a high-glucosinolate mutant caused by overexpression of IQD1 (At3g09710). A series of gain- and loss-of-function IQD1 alleles in different accessions correlates with increased and decreased glucosinolate levels, respectively. IQD1 encodes a novel protein that contains putative nuclear localization signals and several motifs known to mediate calmodulin binding, which are arranged in a plant-specific segment of 67 amino acids, called the IQ67 domain. We demonstrate that an IQD1-GFP fusion protein is targeted to the cell nucleus and that recombinant IQD1 binds to calmodulin in a Ca2+-dependent fashion. Analysis of steady-state messenger RNA levels of glucosinolate pathway genes indicates that IQD1 affects expression of multiple genes with roles in glucosinolate metabolism. Histochemical analysis of tissue-specific IQD1::GUS expression reveals IQD1 promoter activity mainly in vascular tissues of all organs, consistent with the expression patterns of several glucosinolate-related genes. Interestingly, overexpression of IQD1 reduces insect herbivory, which we demonstrated in dual-choice assays with the generalist phloem-feeding green peach aphid (Myzus persicae), and in weight-gain assays with the cabbage looper (Trichoplusia ni), a generalist-chewing lepidopteran. As IQD1 is induced by mechanical stimuli, we propose IQD1 to be novel nuclear factor that integrates intracellular Ca2+ signals to fine-tune glucosinolate accumulation in response to biotic challenge.
Publications

Levy, M.; Rachmilevitch, S.; Abel, S. Transient <em>Agrobacterium</em>-mediated gene expression in the Arabidopsis hydroponics root system for subcellular localization studies Plant Mol. Biol. Rep. 23, 179 - 184, (2005)

To a great extent, the cellular compartmentalization and molecular interactions are indicative of the function of a protein. The development of simple and efficient tools for testing the subcellular location of proteins is indispensable to elucidate the function of genes in plants. In this report, we assessed the feasibility ofAgrobacterium-mediated transformation of hydroponically grown roots to follow intracellular targeting of proteins fused to green fluorescent protein (GFP). We developed a simple in planta assay for subcellular localization of proteins inArabidopsis roots via transient transformation and tested this method by expressing a GFP fusion of a known nuclear protein, IQD1. Visualization of transiently expressed GFP fusion proteins in roots by means of confocal microscopy is superior to the analysis of green tissues because the roots are virtually transparent and free of chlorophyll autofluorescence.
Publications

Ebeler, S.E.; Dingley, K.H.; Ubick, E.; Abel, S.; Mitchell, A.E.; Burns, S.A.; Steinberg, F.M.; Clifford, A.J. Animal models and analytical approaches for understanding the relationships between wine and cancer Drugs Exptl Clin Res 31, 19 - 27, (2005)

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Publications

Grubb, C.D.; Zipp, J.P.; Ludwig-Müller, J.; Masuno, M.N.; Molinski, T.F.; Abel, S. Arabidopsis glucosyltransferase UGT74B1 functions in glucosinolate biosynthesis and auxin homeostasis Plant J 40, 893-908, (2004)

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Publications

Ticconi, C.A.; Abel, S. Short on phosphate: plant surveillance and countermeasures Trends Plant Sci 9, 548-555, (2004)

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Publications

Ticconi, C.A.; Delatorre, C.A.; Lahner, B.; Salt, D.E.; Abel, S. Arabidopsis <span style="font-style: italic;">pdr2</span> reveals a phosphate-sensitive checkpoint in root development Plant Journal 37, 801 - 814, (2004)

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Publications

Dingley, K.H.; Ubick, E.A.; Chiarappa-Zucca, M.L.; Nowell, S.; Abel, S.; Ebeler, S.E.; Mitchell, A.E.; Burns, S.A.; Steinberg, F.M.; Clifford, A.J. Effect of dietary constituents with chemopreventive potential on adduct formation of a low dose of the heterocyclic amines PhIP and IQ and Phase II hepatic enzymes Nutr & Cancer 46, 212 - 221, (2003)

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Publications

Wang, Q.; Grubb, C.D.; Abel, S. Direct analysis of single leaf disks for chemopreventive glucosinolates Phytochem Anal 13, 152 - 157, (2002) DOI: 10.1002/pca.636

Natural isothiocyanates, produced during plant tissue damage from methionine-derived glucosinolates, are potent inducers of mammalian phase 2 detoxification enzymes such as quinone reductase (QR). A greatly simplified bioassay for glucosinolates based on induction and colorimetric detection of QR activity in murine hepatoma cells is described. It is demonstrated that excised leaf disks of Arabidopsis thaliana (ecotype Columbia) can directly and reproducibly substitute for cell-free leaf extracts as inducers of murine QR, which reduces sample preparation to a minimum and maximizes throughput. A comparison of 1 and 3 mm diameter leaf disks indicated that QR inducer potency was proportional to disk circumference (extent of tissue damage) rather than to area. When compared to the QR inducer potency of the corresponding amount of extract, 1 mm leaf disks were equally effective, whereas 3 mm disks were 70% as potent. The QR inducer potency of leaf disks correlated positively with the content of methionine-derived glucosinolates, as shown by the analysis of wild-type plants and mutant lines with lower or higher glucosinolate content. Thus, the microtitre plate-based assay of single leaf disks provides a robust and inexpensive visual method for rapidly screening large numbers of plants in mapping populations or mutant collections and may be applicable to other glucosinolate-producing species.
Publications

Grubb, C.D.; Gross, H.B.; Chen, D.L.; Abel, S. Identification of <em>Arabidopsis</em> mutants with altered glucosinolate profiles based on isothiocyanate bioactivity Plant Sci 162, 143 - 152, (2002) DOI: 10.1016/S0168-9452(01)00550-7

Glucosinolates are a diverse class of nitrogen- and sulfur-containing secondary metabolites. They are rapidly hydrolyzed on tissue disruption to a number of biologically active compounds that are increasingly attracting interest as anticarcinogenic phytochemicals and crop protectants. Several glucosinolate-derived isothiocyanates are potent chemopreventive agents that favorably modulate carcinogen metabolism in mammals. Methylsulfinylalkyl isothiocyanates, in particular the 4-methylsulfinylbutyl derivative, are selective and potent inducers of mammalian detoxification enzymes such as quinone reductase (QR). Cruciferous plants including Arabidopsis thaliana (L.) Heyhn, synthesize methylsulfinylalkyl glucosinolates, which are derived from methionine. Using a colorimetric assay for QR activity in murine hepatoma cells and high performance liquid chromatography (HPLC) analysis of desulfoglucosinolates, we have demonstrated a strong positive correlation between leaf QR inducer potency and leaf content of methionine-derived glucosinolates in various A. thaliana ecotypes and available glucosinolate mutants. In a molecular genetic approach to glucosinolate biosynthesis, we screened 3000 chemically mutagenized M2 plants of the Columbia ecotype for altered leaf QR inducer potency. Subsequent HPLC analysis of progeny of putative mutants identified six lines with significant and heritable changes in leaf glucosinolate content and composition.
Publications

Abel, S.; Ticconi, C.A.; Delatorre, C.A. Phosphate sensing in higher plants Plant Physiology 115, 1 - 8, (2002)

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