Itraq Analysis Reveals Mechanisms Of Imazethapyr Enanotioselective-effects On Root Growth Of Arabidopsis Thaliana

With the development of agriculture,pesticides are widely used as an effective method for pest control.The use of pesticides greatly reduces labor and increases crop yield,but extensive usage of pesticides results in environmental pollution.Herbicide as a kind of commonly used pesticide was remained in soil or water for a long time,and endangered to non-target plants to destroy their growth and development.In this study,we investigated enantioselective effect of IM in Arabidopsis thaliana on root morphology,protein expression and rhizosphere microbe community.The results showed that the seedling fresh weight decreased by 32.0%and 10.8%,after 20μg/L R-(-)-and S-(+)-IM treatment,respectively;and the root fresh weight reduced by 56.5%and 43.5%,respectively.IM treatment enantioselectively affected root structure,and R-(-)-IM was the more effective inhibitor in the damage of A.thaliana growth with shorter root volume,surface area,fewer of tip number and thicker root diamete in comparison to the S-(+)-IM group at equal concentration.The change of root morphology affected nutrients absorption directly.R-(-)-IM reduced the content of Na,Mg and Zn ion in roots to be 61.4%、52.1%and 57.8%of control,respectively;while the content of Na,Mg and Zn ion in roots decreased to be 74.2%、69.9%and 81.9%of control after S-(+)-IM treatment,respectively.Isobaric tags for relative and absolute quantitation(iTRAQ)-based quantitative proteomic approach determined changes of protein expression in A.thaliana roots,and 6135 proteins were identified.Among the 6135 identified proteins,4185 and 3802 proteins were quantified in R-(-)-and S-(+)-IM treatment,respectively.With 1.3-fold as cutoff threshold,1322 and 987 proteins were determined upon R-(-)-and S-(+)-IM treatment,respectively.Among these proteins,892 and 685 proteins were up-regulated by R-(-)-and S-(+)-IM treatment,respectively.Among the up-regulated proteins,354 proteins were overlapped.In addition,430 and 302 proteins were down-regulated by R-(-)-and S-(+)-IM treatment,respectively.Of the two groups of down-regulated proteins,151 proteins were overlapped.Bioinformatic analysis showed that the quantifiable proteins were annotated in amino acid synthesis and metabolism,phenylpropanoid pathway,antioxidant process,sucrose and starch metabolism,tricarboxylic acid cycle(TCA)and protein translation,etc.In addition,IM affected root microbial community structure with significant increase in bacterial abundance and diversity.Acidovorax became a dominant bacteria with the rate increased to 37%and 21%after R-(-)-and S-(+)-IM treatment,respectively.This may be related to induce the secretion of organic acids in root under IM stress.Acidovorax used organic acids as carbon source and gathered to be dominant bacteria on root surface.Taken together,these results suggested a possible mechanism of IM enantioselective effects on growth inhibition of plants and microenvironment of plant survival by impacting multiple biological process and metabolic pathways.