Knockout of Arabidopsis thaliana VEP1, Encoding a PRISE (Progesterone 5β-Reductase/Iridoid Synthase-Like Enzyme), Leads to Metabolic Changes in Response to Exogenous Methyl Vinyl Ketone (MVK)

Small or specialized natural products (SNAPs) produced by plants vary greatly in structure and function, leading to selective advantages during evolution. With a limited number of genes available, a high promiscuity of the enzymes involved allows the generation of a broad range of SNAPs in complex metabolic networks. Comparative metabolic studies may help to understand why—or why not—certain SNAPs are produced in plants. Here, we used the wound-induced, vein patterning regulating VEP1 (AtStR1, At4g24220) and its paralogue gene on locus At5g58750 (AtStR2) from Arabidopsis to study this issue. The enzymes encoded by VEP1-like genes were clustered under the term PRISEs (progesterone 5β-reductase/iridoid synthase-like enzymes) as it was previously demonstrated that they are involved in cardenolide and/or iridoid biosynthesis in other plants. In order to further understand the general role of PRISEs and to detect additional more “accidental” roles we herein characterized A. thaliana steroid reductase 1 (AtStR1) and compared it to A. thaliana steroid reductase 2 (AtStR2). We used A. thaliana Col-0 wildtype plants as well as VEP1 knockout mutants and VEP1 knockout mutants overexpressing either AtStR1 or AtStR2 to investigate the effects on vein patterning and on the stress response after treatment with methyl vinyl ketone (MVK). Our results added evidence to the assumption that AtStR1 and AtStR2, as well as PRISEs in general, play specific roles in stress and defense situations and may be responsible for sudden metabolic shifts.

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Radical mechanisms of methyl vinyl ketone oligomerization through aqueous phase OH-oxidation: on the paradoxical role of dissolved molecular oxygen

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-2913-2013 ◽

2013 ◽

Vol 13 (1) ◽

pp. 2913-2954 ◽

Cited By ~ 2

Author(s):

P. Renard ◽

F. Siekmann ◽

A. Gandolfo ◽

J. Socorro ◽

G. Salque ◽

...

Keyword(s):

Aqueous Phase ◽

High Resolution Mass Spectrometry ◽

Organic Aerosol ◽

Vinyl Ketone ◽

Methyl Vinyl Ketone ◽

Chemical Mechanism ◽

Methyl Vinyl ◽

Phase Chemistry ◽

Dissolved O2

Abstract. It is now accepted that one of the important pathways of Secondary Organic Aerosol (SOA) formation occurs through aqueous phase chemistry in the atmosphere. However, the liquid phase chemical mechanisms leading to macromolecules are still not well understood. For α-dicarbonyl precursors, such as methylglyoxal and glyoxal, radical reactions through OH-oxidation produce oligomers, irreversibly and faster than accretion reactions. Methyl vinyl ketone (MVK) was chosen in the present study as it is an α, β-unsaturated carbonyl that can undergo such reaction pathways in the aqueous phase and forms even high molecular weight oligomers. We present here experiments on the aqueous phase OH-oxidation of MVK, performed under atmospheric relevant conditions. Using NMR and UV absorption spectroscopy, high and ultra-high resolution mass spectrometry, we show that the fast formation of oligomers up to 1800 Da is due to radical oligomerization of MVK, and 13 series of oligomers (out of a total of 26 series) are identified. The influence of atmospherically relevant parameters such as temperature, initial concentrations of MVK and dissolved oxygen are presented and discussed. In agreement with the experimental observations, we propose a chemical mechanism of OH-oxidation of MVK in the aqueous phase that proceeds via radical oligomerization of MVK on the olefin part of the molecule. This mechanism highlights the paradoxical role of dissolved O2: while it inhibits oligomerization reactions, it contributes to produce oligomerization initiator radicals, which rapidly consume O2, thus leading to the supremacy of oligomerization reactions after several minutes of reaction. These processes, together with the large ranges of initial concentrations investigated (60–656 μM of dissolved O2 and 0.2–20 mM of MVK) show the fundamental role that O2 likely plays in atmospheric organic aerosol.

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Technical note: Conversion of isoprene hydroxy hydroperoxides (ISOPOOHs) on metal environmental simulation chamber walls

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-4053-2017 ◽

2017 ◽

Vol 17 (6) ◽

pp. 4053-4062 ◽

Cited By ~ 4

Author(s):

Anne-Kathrin Bernhammer ◽

Martin Breitenlechner ◽

Frank N. Keutsch ◽

Armin Hansel

Keyword(s):

Gas Phase ◽

Technical Note ◽

Vinyl Ketone ◽

Heterogeneous Reactions ◽

Methyl Vinyl Ketone ◽

Oxidation Products ◽

Chemical Mechanism ◽

Stainless Steel Surface ◽

Methyl Vinyl

Abstract. Sources and sinks of isoprene oxidation products from low-NOx isoprene chemistry have been studied at the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber with a custom-built selective reagent ion time-of-flight mass spectrometer (SRI-ToF-MS), which allows quantitative measurement of isoprene hydroxy hydroperoxides (ISOPOOHs). The measured concentrations of the main oxidation products were compared to chemical box model simulations based on the Leeds Master Chemical Mechanism (MCM) v3.3. The modeled ISOPOOH concentrations are a factor of 20 higher than the observed concentrations, and methyl vinyl ketone (MVK) and methacrolein (MACR) concentrations are up to a factor of 2 lower compared to observations, despite the artifact-free detection method. Addition of catalytic conversion of 1,2-ISOPOOH and 4,3-ISOPOOH to methyl vinyl ketone (MVK) and methacrolein (MACR) on the stainless-steel surface of the chamber to the chemical mechanism resolves the discrepancy between model predictions and observation. This suggests that isoprene chemistry in a metal chamber under low-NOx conditions cannot be described by a pure gas phase model alone. Biases in the measurement of ISOPOOH, MVK, and MACR can be caused not only intra-instrumentally but also by the general experimental setup. The work described here extends the role of heterogeneous reactions affecting gas phase composition and properties from instrumental surfaces, described previously, to general experimental setups. The role of such conversion reactions on real environmental surfaces is yet to be explored.

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The role of the iodine-atom adduct in the synthesis and kinetics of methyl vinyl ketone oxide—a resonance-stabilized Criegee intermediate

Physical Chemistry Chemical Physics ◽

10.1039/d0cp02085k ◽

2020 ◽

Vol 22 (24) ◽

pp. 13603-13612 ◽

Cited By ~ 1

Author(s):

Yen-Hsiu Lin ◽

Yu-Lin Li ◽

Wen Chao ◽

Kaito Takahashi ◽

Jim Jr-Min Lin

Keyword(s):

Iodine Atom ◽

Vinyl Ketone ◽

Methyl Vinyl Ketone ◽

Major Pathway ◽

Methyl Vinyl ◽

Kinetics Of

The adduct decomposition is the major pathway that forms CH3(C2H3)COO (MVKO) + I via the reaction of CH3(C2H3)CI + O2 for P > 50 Torr. The related kinetics of the adduct and MVKO + SO2 reactions have been studied over 4–700 Torr and 278–319 K.

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Radical mechanisms of methyl vinyl ketone oligomerization through aqueous phase OH-oxidation: on the paradoxical role of dissolved molecular oxygen

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-6473-2013 ◽

2013 ◽

Vol 13 (13) ◽

pp. 6473-6491 ◽

Cited By ~ 35

Author(s):

P. Renard ◽

F. Siekmann ◽

A. Gandolfo ◽

J. Socorro ◽

G. Salque ◽

...

Keyword(s):

Aqueous Phase ◽

High Resolution Mass Spectrometry ◽

Vinyl Ketone ◽

Methyl Vinyl Ketone ◽

Chemical Mechanism ◽

Radical Oxidation ◽

Methyl Vinyl ◽

Chemical Mechanisms ◽

Phase Chemistry

Abstract. It is now accepted that one of the important pathways of secondary organic aerosol (SOA) formation occurs through aqueous phase chemistry in the atmosphere. However, the chemical mechanisms leading to macromolecules are still not well understood. It was recently shown that oligomer production by OH radical oxidation in the aerosol aqueous phase from α-dicarbonyl precursors, such as methylglyoxal and glyoxal, is irreversible and fast. Methyl vinyl ketone (MVK) was chosen in the present study as it is an α,β-unsaturated carbonyl that can undergo radical oligomerization in the aerosol aqueous phase. We present here experiments on the aqueous phase OH-oxidation of MVK, performed under various conditions. Using NMR and UV absorption spectroscopy, high and ultra-high resolution mass spectrometry, we show that the fast formation of oligomers up to 1800 Da is due to radical oligomerization of MVK, and 13 series of oligomers (out of a total of 26 series) are identified. The influence of atmospherically relevant parameters such as temperature, initial concentrations of MVK and dissolved oxygen are presented and discussed. In agreement with the experimental observations, we propose a chemical mechanism of OH-oxidation of MVK in the aqueous phase that proceeds via radical oligomerization of MVK on the olefin part of the molecule. This mechanism highlights in our experiments the paradoxical role of dissolved O2: while it inhibits oligomerization reactions, it contributes to produce oligomerization initiator radicals, which rapidly consume O2, thus leading to the dominance of oligomerization reactions after several minutes of reaction. These processes, together with the large range of initial concentrations investigated show the fundamental role that radical oligomerization processes likely play in polluted fogs and atmospheric aerosol.

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