Glycinergic–Fipronil Uptake Is Mediated by an Amino Acid Carrier System and Induces the Expression of Amino Acid Transporter Genes in Ricinus communis Seedlings

Abstract

Phloem-mobile insecticides are efficient for piercing and sucking insect control. Introduction of sugar or amino acid groups to the parent compound can improve the phloem mobility of insecticides, so a glycinergic−fipronil conjugate (GlyF), 2- (3-(3-cyano-1-(2,6-dichloro-4-(trifluoromethyl)phenyl)-4-((trifluoromethyl)sulfinyl)-1H-pyrazole-5-yl)ureido) acetic acid, was designed and synthesized. Although the "Kleier model" predicted that this conjugate is not phloem mobile, GlyF can be continually detected during a 5 h collection of Ricinus communis phloem sap. Furthermore, an R. communis seedling cotyledon disk uptake experiment demonstrates that the uptake of GlyF is sensitive to pH, carbonyl cyanide m-chlorophenylhydrazone (CCCP), temperature, and p-chloromercuribenzenesulfonic acid (pCMBS) and is likely mediated by amino acid carrier system. To explore the roles of amino acid transporters (AATs) in GlyF uptake, a total of 62 AAT genes were identified from the R. communis genome in silico. Phylogenetic analysis revealed that AATs in R. communis were organized into the ATF (amino acid transporter) and APC (amino acid, polyaminem and choline transporter) superfamilies, with five subfamilies in ATF and two in APC. Furthermore, the expression profiles of 20 abundantly expressed AATs (cycle threshold (Ct) values <27) were analyzed at 1, 3, and 6 h after GlyF treatment by RT-qPCR. The results demonstrated that expression levels of four AAT genes, RcLHT6, RcANT15, RcProT2, and RcCAT2, were induced by the GlyF treatment in R. communis seedlings. On the basis of the observation that the expression profile of the four candidate genes is similar to the time course observation for GlyF foliar disk uptake, it is suggested that those four genes are possible candidates involved in the uptake of GlyF. These results contribute to a better understanding of the mechanism of GlyF uptake as well as phloem loading from a molecular biology perspective and facilitate functional characterization of candidate AAT genes in future studies.

Vectorizing agrochemicals: enhancing bioavailability via carrier‐mediated transport

“…Glucose and amino acid promoieties were introduced into insecticides to develop phloem‐targeted proinsecticides (Table ). The resulting derivatives included glycinyl fipronil conjugate, sugar‐fipronil conjugates, D‐glucose‐rotenone conjugates, glycinergic‐fipronil conjugate, and amino acid‐chlorantraniliprole conjugates . Despite their parent compounds lack of mobility in the phloem, several of the above mentioned insecticide conjugates had good phloem systemicity .…”

Vectorisation of agrochemicals via amino acid carriers: influence of the spacer arm structure on the phloem mobility of phenylpyrrole conjugates in the Ricinus system

“…). At 6 h, its concentration in the phloem sap (about 30 µ m ) was 2.5 times higher than those of conjugate L‐13 and a glycinergic‐fipronil conjugate recently synthesised …”

“…Carrier‐mediated processes have been shown to be a promising approach to enhancing the uptake and vectorisation of pesticides by utilising plant sugar or amino acid transporters as well . Both glucose and amino acid pesticide conjugates were reported to involve carrier‐mediated uptake and displayed phloem mobility . This propesticide strategy could be applied to develop phloem mobile insecticides, which are needed to control root or vascular pests .…”

“…Both glucose and amino acid pesticide conjugates were reported to involve carrier‐mediated uptake and displayed phloem mobility . This propesticide strategy could be applied to develop phloem mobile insecticides, which are needed to control root or vascular pests . Similarly, profungicides designed to move at long distance in the phloem tissue could be applied to control vascular or root diseases of herbaceous cultures, i.e.…”

Novel amino acid ester–chlorantraniliprole conjugates: design, synthesis, phloem accumulation and bioactivity

“…For instance, the Bonnemain group has reported several derivatives of existing herbicides modified with an α ‐amino acid fragment that exhibit good phloem mobility . In our previous work, a series of glucose–fipronil conjugates (GTF and GOF) and a glycinergic–fipronil conjugate (GlyF) that show distinctive distributions in Ricinus communis have been designed . The uptake of these conjugates was proven to be mediated by an endogenous carrier system .…”