Some compounds containing glucose are absorbed via the monosaccharide transporters of the plasma membrane. A glucose-fipronil conjugate, N-[3-cyano-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazol-5-yl]-1-(β-d-glucopyranosyl)-1H-1,2,3-triazole-4-methanamine (GTF), has been synthesized in our previous work. GTF exhibits moderate phloem mobility in Ricinus communis. In the current paper, we demonstrate that the uptake of GTF by Ricinus seedling cotyledon discs is partly mediated by an active carrier system (K(m)1 = 0.17 mM; V(max)1 = 2.2 nmol cm(-2) h(-1)). Four compounds [d-glucose, sucrose, phloridzin, and carbonyl cyanide m-chlorophenylhydrazone (CCCP)] were examined for their effect on GTF uptake. Phloridzin as well as CCCP markedly inhibit GTF uptake, and d-glucose weakly competes with it. The phloem transport of GTF in Ricinus seedlings is found to involve an active carrier-mediated mechanism that effectively contributes to the GTF phloem loading. The results prove that adding a glucose core is a reasonable and feasible approach to confer phloem mobility to fipronil by utilizing plant monosaccharide transporters.
Design and discovery of carrier-mediated modified pesticides are vital for reducing pesticide dosage and increasing utilization, yet it remains a great challenge due to limited insights into plant translocation mechanisms. Nanostructure/nanoparticle assisted laser desorption/ionization strategy has established itself as a preferential analytical tool for biological tissue analysis, whereas potential applications in plant sciences are hindered with regard to the inability to slice plant leaves and petals. Herein, we report gold nanoparticle (AuNP)-immersed paper imprinting mass spectrometry imaging (MSI) for the spatiotemporal visualization of pesticide translocation in plant leaves. This approach plays a dual role in preserving spatial information and improving ionization efficiency for pesticides regardless of imaging artifacts due to homogenous AuNP deposition. Using this MSI platform, we proposed the elaborate plant translocation mechanism of agrochemicals for the first time, which is currently poorly understood. The dynamic processes of carrier-mediated pesticides can be clearly visualized, including crossing of plasma membranes by transporters, translocation downward in stems through the phloem, diffusion to the xylem and, conversely, accumulation at margins of the treated leaves. Moreover, this AuNP-assisted paper imprinting method could be highly compatible with laser-based MSI instruments, expediting researches across a broad range of fields, especially in nanomaterial development and life sciences.
Understanding of the transporters
involved in the uptake and translocation of agrochemicals in plants
could provide an opportunity to guide pesticide to the site of insect
feeding. The product of Arabidopsis thaliana gene AtLHT1 makes a major contribution to the uptake into the
roots of free amino acids and some of their derivatives. Here, a chlorantraniliprole–glycine
conjugate (CAP-Gly-1) was tested for its affinity to AtLHT1 both in planta and in vitro. Seedlings deficient
in AtLHT1 exhibited a reduction with respect to both
the uptake and root-to-shoot transfer of CAP-Gly-1; plants in which AtLHT1 was constitutively expressed were more effective
than wild type in term of their root uptake of CAP-Gly-1. Protoplast
patch clamping showed that the presence in the external medium of
CAP-Gly-1 was able to induce AtLHT1 genotype-dependent
inward currents. An electrophysiology-based experiment carried out
in Xenopus laevis oocytes expressing AtLHT1 showed that AtLHT1 had a high in vitro affinity
for CAP-Gly-1. The observations supported the possibility of exploiting
AtLHT1 as a critical component of a novel delivery system for amino
acid-based pesticide conjugates.
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