54 research outputs found
Rapid Phytotransformation of Benzotriazole Generates Synthetic Tryptophan and Auxin Analogs in <i>Arabidopsis</i>
Benzotriazoles
(BTs) are xenobiotic contaminants widely distributed
in aquatic environments and of emerging concern due to their polarity,
recalcitrance, and common use. During some water reclamation activities,
such as stormwater bioretention or crop irrigation with recycled water,
BTs come in contact with vegetation, presenting a potential exposure
route to consumers. We discovered that BT in hydroponic systems was
rapidly (approximately 1-log per day) assimilated by Arabidopsis plants and metabolized to novel BT metabolites
structurally resembling tryptophan and auxin plant hormones; <1%
remained as parent compound. Using LC-QTOF-MS untargeted metabolomics,
we identified two major types of BT transformation products: glycosylation
and incorporation into the tryptophan biosynthetic pathway. BT amino
acid metabolites are structurally analogous to tryptophan and the
storage forms of auxin plant hormones. Critical intermediates were
synthesized (authenticated by <sup>1</sup>H/<sup>13</sup>C NMR) for
product verification. In a multiple-exposure temporal mass balance,
three major metabolites accounted for >60% of BT. Glycosylated
BT
was excreted by the plants into the hydroponic medium, a phenomenon
not observed previously. The observed amino acid metabolites are likely
formed when tryptophan biosynthetic enzymes substitute synthetic BT
for native indolic molecules, generating potential phytohormone mimics.
These results suggest that BT metabolism by plants could mask the
presence of BT contamination in the environment. Furthermore, BT-derived
metabolites are structurally related to plant auxin hormones and should
be evaluated for undesirable biological effects
Plant Assimilation Kinetics and Metabolism of 2‑Mercaptobenzothiazole Tire Rubber Vulcanizers by <i>Arabidopsis</i>
2-Mercaptobenzothiazole
(MBT) is a tire rubber vulcanizer found
in potential sources of reclaimed water where it may come in contact
with vegetation. In this work, we quantified the plant assimilation
kinetics of MBT using <i>Arabidopsis</i> under hydroponic
conditions. MBT depletion kinetics in the hydroponic medium with plants
were second order (<i>t</i><sub>1/2</sub> = 0.52 to 2.4
h) and significantly greater than any abiotic losses (>18 times
faster; <i>p</i> = 0.0056). MBT depletion rate was related
to the initial
exposure concentration with higher rates at greater concentrations
from 1.6 μg/L to 147 μg/L until a potentially inhibitory
level (1973 μg/L<b>)</b> lowered the assimilation rate.
9.8% of the initial MBT mass spike was present in the plants after
3 h and decreased through time. In-source LC-MS/MS fragmentation revealed
that MBT was converted by <i>Arabidopsis</i> seedlings to
multiple conjugated-MBT metabolites of differential polarity that
accumulate in both the plant tissue and hydroponic medium; metabolite
representation evolved temporally. Multiple novel MBT-derived plant
metabolites were detected via LC-QTOF-MS analysis; proposed transformation
products include glucose and amino acid conjugated MBT metabolites.
Elucidating plant transformation products of trace organic contaminants
has broad implications for water reuse because plant assimilation
could be employed advantageously in engineered natural treatment systems,
and plant metabolites in food crops could present an unintended exposure
route to consumers
Root-Secreted Coumarins and the Microbiota Interact to Improve Iron Nutrition in Arabidopsis
Plants benefit from associations with a diverse community of root-colonizing microbes. Deciphering the mechanisms underpinning these beneficial services are of interest for improving plant productivity. We report a plant-beneficial interaction between Arabidopsis thaliana and the root microbiota under iron deprivation that is dependent on the secretion of plant-derived coumarins. Disrupting this pathway alters the microbiota and impairs plant growth in iron-limiting soil. Furthermore, the microbiota improves ironlimiting plant performance via a mechanism dependent on plant iron import and secretion of the coumarin fraxetin. This beneficial trait is strain specific yet functionally redundant across phylogenetic lineages of the microbiota. Transcriptomic and elemental analyses revealed that this interaction between commensals and coumarins promotes growth by relieving iron starvation. These results show that coumarins improve plant performance by eliciting microbe-assisted iron nutrition. We propose that the bacterial root microbiota, stimulated by secreted coumarins, is an integral mediator of plant adaptation to ironlimiting soils
Highly Z- and Enantioselective Ring-Opening/Cross-Metathesis Reactions Catalyzed by Stereogenic-at-Mo Adamantylimido Complexes
The first highly Z- and enantioselective class of ring-opening/cross-metathesis reactions is presented. Transformations are promoted in the presence of 98:98:<2 Z/E) or predominantly (≥87:13 Z/E).National Institutes of Health (U.S.) (Grant GM-59426)National Science Foundation (U.S.) (DBI-0619576
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