AtLHT1 Transporter Can Facilitate the Uptake and Translocation of a Glycinergic-Chlorantraniliprole Conjugate in Arabidopsis thaliana.

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.

Uptake and phloem transport of glucose-fipronil conjugate in Ricinus communis involve a carrier-mediated mechanism.

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-(ß-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.