Publications by authors named "Jacob R MacWilliams"

3 Publications

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Quantification of Methylglyoxal Levels in Cowpea Leaves in Response to Cowpea Aphid Infestation.

Bio Protoc 2020 Oct 20;10(20):e3795. Epub 2020 Oct 20.

Graduate program in Biochemistry and Molecular Biology, University of California, Riverside, USA.

Aphids are a serious pest of crops across the world. Aphids feed by inserting their flexible hypodermal needlelike mouthparts, or stylets, into their host plant tissues. They navigate their way to the phloem where they feed on its sap causing little mechanical damage to the plant. Additionally, while feeding, aphids secrete proteinaceous effectors in their saliva to alter plant metabolism and disrupt plant defenses to gain an advantage over the plant. Even with these arsenals to overcome plant responses, plants have evolved ways to detect and counter with defense responses to curtail aphid infestation. One of such response of cowpea to cowpea aphid infestation, is accumulation of the metabolite methylglyoxal. Methylglyoxal is an α,β-dicarbonyl ketoaldehyde that is toxic at high concentrations. Methylglyoxal levels increase modestly after exposure to a number of different abiotic and biotic stresses and has been shown to act as an emerging defense signaling molecule at low levels. Here we describe a protocol to measure methylglyoxal in cowpea leaves after cowpea aphid infestation, by utilizing a perchloric acid extraction process. The extracted supernatant was neutralized with potassium carbonate, and methylglyoxal was quantified through its reaction with N-acetyl-L-cysteine to form N-α-acetyl-S-(1-hydroxy-2-oxo-prop-1-yl)cysteine, a product that is quantified spectrophotometrically.
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http://dx.doi.org/10.21769/BioProtoc.3795DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7842737PMC
October 2020

AcDCXR Is a Cowpea Aphid Effector With Putative Roles in Altering Host Immunity and Physiology.

Front Plant Sci 2020 15;11:605. Epub 2020 May 15.

Graduate Program in Biochemistry and Molecular Biology, University of California, Riverside, Riverside, CA, United States.

Cowpea, , is a crop that is essential to semiarid areas of the world like Sub-Sahara Africa. Cowpea is highly susceptible to cowpea aphid, , infestation that can lead to major yield losses. Aphids feed on their host plant by inserting their hypodermal needlelike flexible stylets into the plant to reach the phloem sap. During feeding, aphids secrete saliva, containing effector proteins, into the plant to disrupt plant immune responses and alter the physiology of the plant to their own advantage. Liquid chromatography tandem mass spectrometry (LC-MS/MS) was used to identify the salivary proteome of the cowpea aphid. About 150 candidate proteins were identified including diacetyl/L-xylulose reductase (DCXR), a novel enzyme previously unidentified in aphid saliva. DCXR is a member of short-chain dehydrogenases/reductases with dual enzymatic functions in carbohydrate and dicarbonyl metabolism. To assess whether cowpea aphid DCXR (AcDCXR) has similar functions, recombinant AcDCXR was purified and assayed enzymatically. For carbohydrate metabolism, the oxidation of xylitol to xylulose was tested. The dicarbonyl reaction involved the reduction of methylglyoxal, an α-β-dicarbonyl ketoaldehyde, known as an abiotic and biotic stress response molecule causing cytotoxicity at high concentrations. To assess whether cowpea aphids induce methylglyoxal in plants, we measured methylglyoxal levels in both cowpea and pea () plants and found them elevated transiently after aphid infestation. Agrobacterium-mediated transient overexpression of AcDCXR in pea resulted in an increase of cowpea aphid fecundity. Taken together, our results indicate that AcDCXR is an effector with a putative ability to generate additional sources of energy to the aphid and to alter plant defense responses. In addition, this work identified methylglyoxal as a potential novel aphid defense metabolite adding to the known repertoire of plant defenses against aphid pests.
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http://dx.doi.org/10.3389/fpls.2020.00605DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7243947PMC
May 2020

Hyperphosphatemia, hypocalcemia and increased serum potassium concentration as distinctive features of early hypomagnesemia in magnesium-deprived mice.

Magnes Res 2015 Dec;28(4):126-35

Department of Biology, The College at Brockport, State University of New York, 350 New Campus Drive, Brockport, NY 14420, USA.

Magnesium-deficient patients show dysfunctional calcium (Ca(2+)) metabolism due to defective parathyroid hormone (PTH) secretion. In mice and rats, long-term magnesium (Mg(2+)) deprivation causes hyperphosphaturia and increases fibroblast growth factor 23 (FGF23) secretion, despite normal serum phosphate (Pi) and Ca(2+). Electrolyte disturbances during early hypomagnesemia may explain the response of mice to long-term Mg(2+) deprivation, but our knowledge of electrolyte homeostasis during this stage is limited. This study compares the effect of both short- and long-term Mg(2+) restriction on the electrolyte balance in mice. Mice were fed control or Mg(2+)-deficient diets for one to three days, one week, or three weeks. Prior to killing the mice, urine was collected over 24 h using metabolic cages. Within 24 h of Mg(2+) deprivation, hypomagnesemia, hypocalcemia and hyperphosphatemia developed, and after three days of Mg(2+) deprivation, serum potassium (K(+)) was increased. These changes were accompanied by a reduction in urinary volume, hyperphosphaturia, hypocalciuria and decreased Mg(2+), sodium (Na(+)) and K(+) excretion. Surprisingly, after one week of Mg(2+) deprivation, serum K(+), Pi and Ca(2+) had normalized, showing that mineral homeostasis is most affected during early hypomagnesemia. Serum Pi and K(+) are known to stimulate secretion of FGF23 and aldosterone, which are usually elevated during Mg(2+) deficiency. Thus, the hyperphosphatemia and increased serum K(+) concentration observed during short-term Mg(2+) deprivation may help our understanding of adaptation to chronic Mg(2+) deficiency.
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http://dx.doi.org/10.1684/mrh.2015.0394DOI Listing
December 2015
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