Evaluating the combined effects of pretilachlor and UV-B on two Azolla species

Ultimate fate, transformation, and toxicological consequences of herbicide pretilachlor to biotic components and associated environment: An overview

Herbicides are applied for effective weed management in order to increase the crop yield. In recent decades, the overuse of these chemicals has posed adverse effects on different biotic components of the environment. Pretilachlor has been widely used during last few decades for weed management in paddy crop. Its excessive use may prove fatal for environment, various organisms, and nontarget plants. Thus, it is pertinent to know the extent to which herbicide residues remain in environment. The potential mobility and the release rate of herbicide in the soil are important factors governing ecotoxicological impact and degradation rate. Therefore, several techniques are being investigated for its effective removal from the contaminated sites. Furthermore, efforts have also been made to study the degradation of pretilachlor by various physicochemical processes, resulting into the formation of different types of metabolites. This review summarizes the available information on environmental fate, various degradation processes, microbial biotransformation, metabolites formed, ecotoxicological effects, techniques for detection in environmental samples, effect of safener, and various control release formulations for sustained release of pretilachlor in applied fields. The information so obtained will be very advantageous in deciding the future policies for safe and judicious use of the herbicide by maintaining health and environmental sustainability.

New Insights into Radio-Resistance Mechanism Revealed by (Phospho)Proteome Analysis of Deinococcus Radiodurans after Heavy Ion Irradiation

Deinococcus radiodurans (D. radiodurans) can tolerate various extreme environments including radiation. Protein phosphorylation plays an important role in radiation resistance mechanisms; however, there is currently a lack of systematic research on this topic in D. radiodurans. Based on label-free (phospho)proteomics, we explored the dynamic changes of D. radiodurans under various doses of heavy ion irradiation and at different time points. In total, 2359 proteins and 1110 high-confidence phosphosites were identified, of which 66% and 23% showed significant changes, respectively, with the majority being upregulated. The upregulated proteins at different states (different doses or time points) were distinct, indicating that the radio-resistance mechanism is dose- and stage-dependent. The protein phosphorylation level has a much higher upregulation than protein abundance, suggesting phosphorylation is more sensitive to irradiation. There were four distinct dynamic changing patterns of phosphorylation, most of which were inconsistent with protein levels. Further analysis revealed that pathways related to RNA metabolism and antioxidation were activated after irradiation, indicating their importance in radiation response. We also screened some key hub phosphoproteins and radiation-responsive kinases for further study. Overall, this study provides a landscape of the radiation-induced dynamic change of protein expression and phosphorylation, which provides a basis for subsequent functional and applied studies.

Reactive oxygen species signaling and stomatal movement: Current updates and future perspectives

Reactive oxygen species (ROS), a by-product of aerobic metabolism were initially studied in context to their damaging effect but recent decades witnessed significant advancements in understanding the role of ROS as signaling molecules. Contrary to earlier views, it is becoming evident that ROS production is not necessarily a symptom of cellular dysfunction but it might represent a necessary signal in adjusting the cellular machinery according to the altered conditions. Stomatal movement is controlled by multifaceted signaling network in response to endogenous and environmental signals. Furthermore, the stomatal aperture is regulated by a coordinated action of signaling proteins, ROS-generating enzymes, and downstream executors like transporters, ion pumps, plasma membrane channels, which control the turgor pressure of the guard cell. The earliest hallmarks of stomatal closure are ROS accumulation in the apoplast and chloroplasts and thereafter, there is a successive increase in cytoplasmic Ca2+ level which rules the multiple kinases activity that in turn regulates the activity of ROS-generating enzymes and various ion channels. In addition, ROS also regulate the action of multiple proteins directly by oxidative post translational modifications to adjust guard cell signaling. Notwithstanding, an active progress has been made with ROS signaling mechanism but the regulatory action for ROS signaling processes in stomatal movement is still fragmentary. Therefore, keeping in view the above facts, in this mini review the basic concepts and role of ROS signaling in the stomatal movement have been presented comprehensively along with recent highlights.

Interactive effects of herbicide and enhanced UV-B on growth, oxidative damage and the ascorbate-glutathione cycle in two Azolla species

A field experiment was conducted to investigate the impact of alone and combined exposures of herbicide pretilachlor (5, 10 and 20μgml(-1)) and enhanced UV-B radiation (UV-B1; ambient +2.2kJm(-2) day(-1) and UV-B2; ambient +4.4kJm(-2) day(-1)) on growth, oxidative stress and the ascorbate-glutathione (AsA-GSH) cycle in two agronomically important Azolla spp. viz., Azolla microphylla and Azolla pinnata. Decreased relative growth rate (RGR) in both the species under tested stress could be linked to enhanced oxidative stress, thus higher H2O2 accumulation was observed, that in turn might have caused severe damage to lipids and proteins, thereby decreasing membrane stability. The effects were exacerbated when spp. were exposed to combined treatments of enhanced UV-B and pretilachlor. Detoxification of H2O2 is regulated by enzymes/metabolites of AsA-GSH cycle such as ascorbate peroxidase (APX) and glutathione reductase (GR) activity that were found to be stimulated. While, dehydroascorabte reductase (DHAR) activity, and the amount of metabolites: ascorbate (AsA), glutathione (GSH) and ratios of reduced/oxidized AsA (AsA/DHA) and GSH (GSH/GSSG), showed significant reduction with increasing doses of both the stressors, either applied alone or in combination. Glutathione-S-transferase (GST), an enzyme involved in scavenging of xenobiotics, was found to be stimulated under the tested stress. This study suggests that decline in DHAR activity and in AsA/DHA ratio might have led to enhanced H2O2 accumulation, thus decreased RGR was noticed under tested stress in both the species and the effect was more pronounced in A. pinnata. Owing to better performance of AsA-GSH cycle in A. microphylla, this study substantiates the view that A. microphylla is more tolerant than A. pinnata.

Reactive Oxygen Species (ROS): Beneficial Companions of Plants' Developmental Processes

Reactive oxygen species (ROS) are generated inevitably in the redox reactions of plants, including respiration and photosynthesis. In earlier studies, ROS were considered as toxic by-products of aerobic pathways of the metabolism. But in recent years, concept about ROS has changed because they also participate in developmental processes of plants by acting as signaling molecules. In plants, ROS regulate many developmental processes such as cell proliferation and differentiation, programmed cell death, seed germination, gravitropism, root hair growth and pollen tube development, senescence, etc. Despite much progress, a comprehensive update of advances in the understanding of the mechanisms evoked by ROS that mediate in cell proliferation and development are fragmentry and the matter of ROS perception and the signaling cascade remains open. Therefore, keeping in view the above facts, an attempt has been made in this article to summarize the recent findings regarding updates made in the regulatory action of ROS at various plant developmental stages, which are still not well-known.