Insecticide resistance by a host-symbiont reciprocal detoxification

Insecticide resistance is one of the most serious problems in contemporary agriculture and public health. Although recent studies revealed that insect gut symbionts contribute to resistance, the symbiont-mediated detoxification process remains unclear. Here we report the in vivo detoxification process of an organophosphorus insecticide, fenitrothion, in the bean bug Riptortus pedestris. Using transcriptomics and reverse genetics, we reveal that gut symbiotic bacteria degrade this insecticide through a horizontally acquired insecticide-degrading enzyme into the non-insecticidal but bactericidal compound 3-methyl-4-nitrophenol, which is subsequently excreted by the host insect. This integrated “host-symbiont reciprocal detoxification relay” enables the simultaneous maintenance of symbiosis and efficient insecticide degradation. We also find that the symbiont-mediated detoxification process is analogous to the insect genome-encoded fenitrothion detoxification system present in other insects. Our findings highlight the capacity of symbiosis, combined with horizontal gene transfer in the environment, as a powerful strategy for an insect to instantly eliminate a toxic chemical compound, which could play a critical role in the human-pest arms race.

Arabidopsis P4 ATPase-mediated cell detoxification confers resistance to Fusarium graminearum and Verticillium dahliae

Many toxic secondary metabolites produced by phytopathogens can subvert host immunity, and some of them are recognized as pathogenicity factors. Fusarium head blight and Verticillium wilt are destructive plant diseases worldwide. Using toxins produced by the causal fungi Fusarium graminearum and Verticillium dahliae as screening agents, here we show that the Arabidopsis P4 ATPases AtALA1 and AtALA7 are responsible for cellular detoxification of mycotoxins. Through AtALA1-/AtALA7-mediated vesicle transport, toxins are sequestered in vacuoles for degradation. Overexpression of AtALA1 and AtALA7 significantly increases the resistance of transgenic plants to F. graminearum and V. dahliae, respectively. Notably, the concentration of deoxynivalenol, a mycotoxin harmful to the health of humans and animals, was decreased in transgenic Arabidopsis siliques and maize seeds. This vesicle-mediated cell detoxification process provides a strategy to increase plant resistance against different toxin-associated diseases and to reduce the mycotoxin contamination in food and feed.

Evaluation of the role of Shodhana (Purification) process in Croton tiglium seeds for reduction of toxic content

In Ayurvedic texts, Jayapala or croton tiglium seeds are well known as khumbini for its toxicity (severe purgative action) and are used for the treatment of constipation after shodhana (detoxification) of the seed with godugdha (cow milk). The oil content of the seeds was responsible for the purgative property, and its reduction enhances its medicinal usage. The presence of Crotonoside or iso-guanosine in seed extract was identified in HPTLC and quantified using high pressure liquid chromatography technique both before and after the purification process of the seed. The phytochemicals and physicochemical parameters of seeds were analyzed to find the level of changes in the processed seeds. The other chemical constituents of the seed extracts are studied using different techniques like HPTLC, HPLC, LC-MS, and GC-MS. The study has revealed that the detoxification process, as per classical texts, has shown an effective depletion in the quantity of crotonoside in processed seeds.

Hemozoin (beta-hematin) formation inhibitors; A promising target for the development of new antimalarials: Current update and A future prospect

Background: Malaria is responsible for a social and an economic burden in most low-income malaria-affected countries. Thus, newer antimalarials are needed to tackle morbidities and mortalities associated with the drug-resistant malarial strains. Haemoglobin digestion inside the food vacuole of malarial parasite would lead to producing redox-active and toxic-free heme. The detoxification process adopted by Plasmodium sp. would give rise to hemozoin (Hz) (beta-hematin) formation. Targeting the pathway of hemozoin formation is considered as a validated target for the discovery of newer antimalarials. Objective: This study aims to collect detailed information about aspects of hemozoin (Hz) (beta-hematin) inhibitors. Methods: A systemic search has been carried out using PubMed, Google Scholar, CNKI, etc., for relevant studies having the keyword, ' hemozoin or beta-hematin' for almost the last 2 decades (2000-2021). Results: This mini-review tries to summarize all the recent advancements made for the developments of synthetic, natural isolated phytoconstituents and plant extracts inhibiting the hemozoin (beta-hematin) formation. Conclusion: thus, would act as promising antimalarial candidates in near future.

Growth Hormone-like Activities of Organophosphorus Flame Retardants (OPFRs) in growth of Rice (Oryza sativa L.)

To identify the toxic effect of Organophosphorus Flame Retardants (OPFRs) on plants, six different OPFRs involved in three concentrations (50 µg/L, 100 µg/L and 200 µg/L) were selected to estimate their toxicity to rice growth. The seed germination, seedling growth, OPFRs accumulation and antioxidative defense system were investigated in rice. The results showed that all of OPFRs inhibited the germination of seeds. OPFRs were accumulated in roots and shoots, and the accumulations of OPFRs in roots were higher than in shoots. However, the hormone-like effect of all six OPFRs was found on plants. The growth of seedlings was irrigated by 50 µg/L, 100 µg/L and 200 µg/L OPFRs in our experiment according to fresh weights and lengths of seedlings. And then malondialdehyde (MDA) and antioxidative defense system were impressed after OPFRs exposed 21 d. According to gene expressions of seven antioxidative enzymes at 14 d, most of enzyme expressions were updated to alleviated reactive oxygen species (ROS) by OPFRs exposure. Tris (1, 3-dichloro-2-propyl) phosphate (TDCPP) showed the strongest oxidative toxicity to plants among all of OPFRs. During the early 14 d period, the antioxidant enzymes could play important role in detoxification process. And after 21 d, antioxidants ascorbate (AsA) in roots and glutathione (GSH) in shoots could take over antioxidant enzymes against to OPFRs toxicity.

The Effect of Detoxification of Lignocellulosic Biomass for Enhanced Methane Production

The aim of this research is to examine the effect of lignocellulosic biomass detoxification on the efficiency of the methane fermentation process. Both for corn straw and rye straw, the methane yield was expressed per volume of fermentation medium and per mass of volatile solids (VS) added. Lignocellulosic biomass was subjected of thermo-chemical and enzymatic sequential pretreatments. It was found that methane yield was higher by 22% when using the detoxification process. In these variants, CH4 yield was 18.86 L/L for corn straw and 17.69 L/L for rye straw; while methane yield expressed per mass of VS added was 0.31 m3/kg VS for corn straw and 0.29 m3/kg VS for rye straw. The inclusion of a detoxification step in pretreatments of biomass lignocellulosic increases the degree of organic substance decomposition and enhances methane yield. The results show that a two-step pretreatment, alkaline/enzymatic with a detoxification process, is necessary for the effective generation of high methane concentration biogas.

Expression Analyses of Genes Related to Multixenobiotic Resistance in Mytilus galloprovincialis after Exposure to Okadaic Acid-Producing Dinophysis acuminate

The mussel Mytilus galloprovincialis is one of the most important aquaculture species in Europe. Its main production problem is the accumulation of toxins during coastal blooms, which prevents mussel commercialization. P-glycoprotein (ABCB1/MDR1/P-gp) is part of the multixenobiotic resistance system in aquatic organisms, and okadaic acid, the main DSP toxin, is probably a substrate of the P-gp-mediated efflux. In this study, the presence and possible role of P-gp in the okadaic acid detoxification process was studied in M. galloprovincialis. We identified, cloned, and characterized two complete cDNAs of mdr1 and mdr2 genes. MgMDR1 and MgMDR2 predicted proteins had the structure organization of ABCB full transporters, and were identified as P-gp/MDR/ABCB proteins. Furthermore, the expression of mdr genes was monitored in gills, digestive gland, and mantle during a cycle of accumulation-elimination of okadaic acid. Mdr1 significantly increased its expression in the digestive gland and gills, supporting the idea of an important role of the MDR1 protein in okadaic acid efflux out of cells in these tissues. The expression of M. galloprovincialismrp2, a multidrug associated protein (MRP/ABCC), was also monitored. As in the case of mdr1, there was a significant induction in the expression of mrp2 in the digestive gland, as the content of okadaic acid increased. Thus, P-gp and MRP might constitute a functional defense network against xenobiotics, and might be involved in the resistance mechanisms to DSP toxins.

Cancer risk and nullity of Glutathione-S-transferase mu and theta 1 in occupational pesticide workers

: Occupational exposure to pesticides has been associated with adverse health conditions, including genotoxicity and cancer. Nullity of GSTT1/GSTM1 increases the susceptibility of pesticide workers to these adverse health effects due to lack of efficient detoxification process created by the absence of these key xenobiotic metabolizing enzymes. However, this assertion does not seem to maintain its stance at all the time; some pesticide workers with the null genotypes do not present the susceptibility. This suggests the modulatory role of other confounding factors, genetic and environmental conditions. Pesticides, aggravated by the null GSTT1/GSTM1, cause genotoxicity and cancer through oxidative stress and miRNA dysregulation. Thus, the absence of these adverse health effects together with the presence of null GSTT1/GSTM1 genotypes demands further explanation. Also, understanding the mechanism behind the protection of cells – that are devoid of GSTT1/GSTM1 – from oxidative stress constitutes a great challenge and potential research area. Therefore, this review article highlights the recent advancements in the presence and absence of cancer risk in occupational pesticide workers with GSTT1 and GSTM1 null genotypes.

Biological responses in pesticide exposed lizards (Podarcis siculus)

The release of contaminants as herbicides, fungicides and insecticides into the environment has been listed as one of the six major contributors to the global decline of reptiles. Although reptiles may face severe risk from contaminants due to their ecology and physiology, they are currently less studied than other vertebrate groups. In the present work, we investigated if and how different types of field treatment (conventional and organic) affected the health status of Italian wall lizard (Podarcis siculus) individuals in central Italy. We chose a multi-biomarker approach that evaluated the biological responses of lizards to the treatment by means of AChE activity in the nervous system, biotransformation enzymes activities and oxidative stress in the liver, micronuclei frequency measured in the erythrocytes, and rate of intestinal parasitic infection. Our findings showed evidence of effects of treatment in conventional areas and between sexes with significant oxidative stress due to hydroxyl radicals, that caused DNA damage. No difference of intestinal parasite infections was found among treatments. Podarcis siculus seems to be a good bioindicator in ecotoxicological studies and potentially in risk assessment of pesticides, although further analyses in laboratory and in the field are needed to achieve more accurate quantification of specific pesticide effects in relation to known exposure history and to understand if other mechanisms were involved in the toxicity and detoxification process of pesticides for this species.