The Responses Of Quinclorac Stress On Physiological And Proteomics Levels In Flue-cured Tobacco Leaves

Quinclorac is a hormone type quinoline carboxylic acid herbicide developed by BASF in 1983,mainly used to control barnyard grass and partial broadleaf weeds in rice fields with advantages of low dosage,long residual period and wide application period.Quinclorac is not easy to degrade in the acid soil environment because of weak acidity,and easily causes phytotoxicity for sensitive crop of flue-cured tobacco.At present,there are some researches about phytotoxicity mechanism of quinclorac from morphology and physiological characteristics,and few studies at the molecular level.Therefore,it is necessary to study gene expression,regulation and signal transduction at the molecular level by means of molecular biology technology to reveal the molecular mechanism of action,and to provide scientific theoretical basis for relieving quinclorac phytotoxicity.In this paper,the studies on the degradation dynamics of quinclorac in paddy field,the physiological responses and the differentially expressed proteins of tobacco leaves under quinclorac stress were studied.The results were shown as following:?The degradation of quinclorac in paddy field showed that the degradation of quinclorac in paddy soil was accord with the first-order chemical reaction dynamic equation of C=C_oe^-kt.Dynamic equation was C=0.176e^-0.061t?R²=0.9144?,and the half-life was 11.36 d with application of 50%quinclorac WP 375 a.i.g/hm²?recommended dose?.Dynamic equation was C=0.249e^-0.0314t?R²=0.7155?,and the half-life was 22.07 d with application of 562.5 a.i.g/hm²?1.5 times the recommended dose?.Quinclorac was not easy to degradate because of higher soil acidity in Jiangxi rice-tobacco rotation areas,the soil would remain the residues in soil,and would result in tobacco deformity.This study provided scientific basis for rational utilization of quinclorac in Jiangxi rice-tobacco rotation areas.?Photosynthesis,synthesis and metabolism,defense enzymes and other physiological activities had been undergone some changes responsed to quinclorac stress.Under quinclorac stress,the contents changes of soluble sugar,soluble protein,proline and MDA were different,it was mainly through the accumulation of proline to against quinclorac damage,therefore proline could be as anti index under quinclorc stress.The activities of SOD,POD,CAT and APX were decreased,and the activities change of CAT and SOD were slightly earlier compared to the activities change of POD and APX,indicating that SOD and CAT were more sensitive than POD and APX under quinclorac stress.The photosynthetic rate,transpiration rate,stomatal conductance and intercellular CO₂concentration of tobacco under concentration?1.0×10^-22 mg/kg?of quinclorac stress were significantly different from those of normal tobacco leaves.Quinclorac affected the photosynthesis,blocked the biosynthesis,and caused slow growth of tobacco plants.?In this paper,the quantitative proteomics study of tobacco leaves under quinclorac stress was identified by using iTRAQ technology.The results indicated that 5275quantitative proteins were identified,416 differentially expressed proteins were identified,in which 252 proteins were up-regulated and 164 proteins were down-regulated.GO?Gene ontology?showed that the differentially expressed proteins were mainly involved plastid,thylakoid,cytoplasm,extracellular region extracellular domain,cytosol,intracellular,plasma membrane,nucleus,protein complex and so on.The differentially expressed proteins played a part in oxidoreductase activity,ion binding,RNA binding,transmembrane transporter activity,DNA binding,hydrolase activity-acting on glycosyl bonds,structural constituent of ribosome,lyase activity,peptidase activity and so on.The differentially expressed proteins were mainly enriched in biosynthesis process,transport,small molecule metabolism,response to stress,cellular nitrogen compound metabolic process,photosynthesis and catabolic process,generation of precursor metabolites and energy,carbohydrate metabolic process and so on.KEGG?Kyoto Encyclopedia of Genes and Genomes?pathway were mainly related to carbon metabolism?15.12%?,amino acid biosynthesis?10.47%?,photosynthesis?9.88%?,ribosome?8.72%?,oxidative phosphorylation?6.98%?and so on.STRING analysis was showed that the interaction network of differentially expressed proteins constituted by photosynthesis,synthesis and metabolism,defense and stress,signal transduction,cell transport and protein position,and each protein was regulated by multiple action channels.?The expression levels of differentially expressed proteins were verified by real-time quantitative PCR and the results were not consistent with those of the quantitative mass spectrometry.This study could provide some theoretical basis for analysis of the mechanism of phytotoxicity of quinclorac,the mechanism of anti stress,and relieving phytotoxicity.