Abstract
To develop a new pesticide with phloem mobility, a series of new amino acid–fipronil conjugates were designed and synthesized based on derivatization at the 3-position of the pyrazole ring of fipronil. Experiments using a Ricinus communis seedling system showed that all tested conjugates were phloem mobile except for the isoleucine–fipronil conjugate, and that the serine–fipronil conjugate (4g) exhibited the highest concentration in phloem sap (52.00 ± 5.80 μM). According to prediction with log Cf values and uptake experiments with Xenopus oocytes, the phloem loading process of conjugate 4g involved both passive diffusion and an active carrier system (RcANT15). In particular, compared with for a previously reported glycinergic–fipronil conjugate (GlyF), passive diffusion played a more important role for conjugate 4g in the enhancement of phloem mobility. This study suggests that associating a nutrient at a different position of an existing pesticide structure could still be effective in obtaining phloem-mobile derivatives, but the distinct physicochemical properties of resultant conjugates may lead to different phloem loading mechanisms.
Highlights
Phloem mobility [1,2] of a pesticide is an attribute that contributes positively to its efficacy against piercing and sucking insects, especially pests hidden in nonexposed plant parts such as growing tips and roots [3]
This demonstrated that the ability to penetrate the plasma membrane through passive diffusion dominated the overall phloem loading behavior for the new conjugates with high phloem mobility, and was the key factor that caused the enhanced uptake compared with glycinergic–fipronil conjugate (GlyF) (Table 2)
Was increased by about 0.25, 0.05, and 0.27 nmol/10 cells, respectively. This indicated that the amino acid carrier RcANT15 did promote the uptake of all tested conjugates in Xenopus oocytes, but the significance may be distinct for different conjugates
Summary
Phloem mobility [1,2] of a pesticide is an attribute that contributes positively to its efficacy against piercing and sucking insects, especially pests hidden in nonexposed plant parts such as growing tips and roots [3]. In our previous work, the non-phloem-mobile pesticide fipronil was conjugated with endogenous nutrients including monosaccharides and amino acids to obtain phloem-mobile derivatives, such as glucose–fipronil conjugate (GTF) [14] and glycinergic–fipronil conjugate (GlyF) (Figure 1) [15]. According to the assumption that the additional phloem mobility was led by the affinity between the amino acid fragment on conjugates and amino acid transporters in plants, derivatization at other positions on the parent structure with the same nutrient substituent could lead to phloem-mobile compounds. To support this hypothesis, in this study, a new series. Experiments including prediction with log Cf values and uptake experiments with Xenopus oocytes were conducted to compare the new and previous conjugates, and the results could help provide a deeper understanding of the phloem loading mechanism of similar xenobiotics
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
