Comparison of the Metabolic Behaviors of Six Systemic Insecticides in a Newly Established Cell Suspension Culture Derived from Tea (Camellia sinensis L.) Leaves

Abstract

The use of an in vitro cell suspension to study insecticide metabolism is a simpler strategy compared to using intact plants, especially for a difficult matrix such as tea. In this study, a sterile tea leaf callus was inoculated into B liquid media with 2,4-dichlorophenoxyacetic acid (2,4-D, 1.0 mg L) and Kinetin (KT, 0.1 mg L). After 3-4 subcultures (28 days each), a good cell suspension was established. Utilizing these cultures, the metabolic behaviors of six insecticides, including two organophosphates (dimethoate, omethoate) and four neonicotinoids (thiamethoxam, imidacloprid, acetamiprid, and imidaclothiz) were compared. The results showed that thiamethoxam, dimethoate, and omethoate were easily metabolized by tea cells, with degradation ratios after 75 days of 55.3%, 90.4%, and 100%, respectively. Seven metabolites of thiamethoxan and two metabolites of dimethoate were found in treated cell cultures using mass-spectrometry, compared to only two metabolites for thiamethoxam and one for dimethoate in treated intact plants.

Evaluation of Callus Cultures to Elucidate the Metabolism of Tebuconazole, Flurtamone, Fenhexamid, and Metalaxyl-M in Brassica napus L., Glycine max (L.) Merr., Zea mays L., and Triticum aestivum L.

“…Second, due to the aseptic conditions in plant's callus cultures, all detected metabolites were unambiguous plant metabolites, and it was assumed that no byproducts were formed by microbes or fungi. 15,22 The behavior of callus cultures and plants with the exposed pesticides were not comparable throughout all incubations. In particular, the application of flurtamone as an herbicide gave the possibility to discuss such effects.…”

“…The homogenization step implied possible deficiencies due to heterogenic material or false-positive or -negative sampling. Second, due to the aseptic conditions in plant’s callus cultures, all detected metabolites were unambiguous plant metabolites, and it was assumed that no byproducts were formed by microbes or fungi. , …”

“…Callus cultures are undifferentiated and unorganized cell masses of plant parenchymal tissue used to study metabolic degradation of xenobiotics in plants. − It is well accepted that without any interference from microbial- or fungal microenvironment, aseptic callus cultures can be applied to identify the xenobiotic metabolism . Davidonis et al (1978, 1980, 1982a, b), Feung et al (1976, 1978), Davis et al (1991), Knops et al (1995), Babczinski (1999), and Fujisawa et al (2009) showed the metabolic degradation of 14 C labeled pesticides in cell suspension cultures of various crops. − ,, Feung et al (1978) investigated the metabolic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) in Glycine max L. soybean suspension cultures .…”

“…These projects were nevertheless complex and expensive because of using 14 C labeled chemicals in suspension and furthermore the complex sample preparation protocols for analytical measurements. These two aspects were the most critical time- and cost-consuming steps in metabolism studies and should be avoided in future screening tests …”

“…These two aspects were the most critical time-and cost-consuming steps in metabolism studies and should be avoided in future screening tests. 22 This study aims to establish and validate a screening method for fast identification of metabolic degradation of the used pesticides in crops without using radioactive labeled compounds and complex protocols. The use of state-of-the-art high-resolution mass spectrometry (HRMS) allows the evaluation of metabolic properties at low-intensity signals in complex matrices.…”