Effects of the Herbicide Imazethapyr on Photosynthesis in PGR5- and NDH-DeficientArabidopsis thalianaat the Biochemical, Transcriptomic, and Proteomic Levels

Abstract

Photosynthesis is a very important metabolic pathway for plant growth and crop yield. This report investigated the effect of the herbicide imazethapyr on photosynthesis in the Arabidopsis thaliana pnsB3 mutant (a defect in the NDH pathway) and pgr5 mutant (a defect in the PGR5 pathway) to determine which cyclic electron transport chain (CET) of the NDH and PGR5 pathways is more important for protecting the photosynthetic system under herbicide stress. The results showed that 20 μg/L imazethapyr markedly inhibited the growth of the three ecotypes of A. thaliana and produced more anthocyanins and reactive oxygen species (ROS), particularly in the pgr5 mutant. The chlorophyll fluorescence results showed that PSII was severely damaged in the pgr5 mutant. Additionally, the CET was significantly stimulated to protect the photosynthetic system from light damage in Wt and the pnsB3 mutant but not the pgr5 mutant. The real-time PCR analysis indicated that imazethapyr treatment considerably decreased the transcript levels of most photosynthesis-related genes in the three treated groups. Several genes in the PGR5 pathway were significantly induced in the pnsB3 mutant, but no genes in the NDH pathway were induced in the pgr5 mutant. The gene transcription analysis showed that the pgr5 mutant cannot compensate for the deficit in the PGR5 pathway by stimulating the NDH pathway, whereas the pnsB3 mutant can compensate for the deficit in the CET cycle by regulating the PGR5 pathway. The iTRAQ analyses also showed that the photosynthesis system, glycolysis, and TCA cycle suffered the most severe damage in the pgr5 mutant. All of these results showed that the PGR5 pathway is more critical for electron transfer around PSI than the NDH pathway to resist herbicide stress.

Acetolactate Synthase-Inhibiting Gametocide Amidosulfuron Causes Chloroplast Destruction, Tissue Autophagy, and Elevation of Ethylene Release in Rapeseed

“…In another study, exposure of A. thaliana plants to trace concentration of imazethapyr strongly affected chlorophyll synthesis and increased reactive oxygen species (ROS) (Qian et al, 2011 , 2015 ). Short exposure of rice seedlings to imazethapyr induced damages to lipid membranes and negatively affected the transcription of a number of genes involved photosynthesis, starch and sugar metabolism, and the tricarboxylic acid cycle (Qian et al, 2011 ; Sun et al, 2016 ). Cheng et al ( 2013 ) and Li et al ( 2015 ) also found that, at the vacuolated-microspore stage of MES-treated rapeseed anther, the chloroplasts in the epidermis and endothecium cells exhibited defects.…”

“…Both amidosulfuron (Figure 3 ) and MES exposure (Li et al, 2015 ) led to decrease in soluble sugars content in leaf and flower bud, and therefore, it was assumed that carbohydrate metabolism maybe blocked in these treatments. Moreover, the results of Sun et al ( 2016 ) showed that A. thaliana cultivated in a solution containing 20 μg/L imazethapyr produced more anthocyanins and ROS, particularly in the pgr5 mutant (a defect in the proton gradient regulation 5 pathway). Their results also showed that the PSII was severely damaged and the transcript levels of most photosynthesis-related genes were decreased in the treated plants (Sun et al, 2016 ).…”

“…Moreover, the results of Sun et al ( 2016 ) showed that A. thaliana cultivated in a solution containing 20 μg/L imazethapyr produced more anthocyanins and ROS, particularly in the pgr5 mutant (a defect in the proton gradient regulation 5 pathway). Their results also showed that the PSII was severely damaged and the transcript levels of most photosynthesis-related genes were decreased in the treated plants (Sun et al, 2016 ).…”

“…In summary, destruction of chloroplast and incapability of photosynthesis are two main effects observed in the treatments of sulfonylurea and other ALS-inhibiting gametocides (Qian et al, 2011 ; Cheng et al, 2013 ; Li et al, 2015 ; Saja et al, 2016 ; Sun et al, 2016 ). Moreover, the down-regulation of chloroplastic PPD2 intimated structural and/or functional abnormalities of chloroplast.…”

Selectivity of Imazapic + Imazapyr Herbicides on Irrigated Rice as Affected by Seed Treatment with Dietholate and Clomazone Applied in Preemergence

“…As oxidative stress increases, there is a cascade reaction with increased lipid peroxidation, membrane damage, protein damage, especially ATP synthase and vacuolar ATPase (V-ATPase), nucleic acids and thylakoids, which lose their ability to perform photosynthesis (Neilson et al, 2010). The application of herbicides leads to changes in photosynthesis and the increase of ROS in peanut, arabidopsis, rice and wheat plants (Agostinetto et al, 2016;Nohatto et al, 2016;Radwan and Fayez, 2016;Sun et al, 2016).…”