Study On The Peptidomics Of Maize Under Rhizoctonia Solani Stress

Peptidomics is an emerging field for qualitative and quantitative analysis peptides in organisms.It is derived from proteomics and based on modern separation,analysis and computational techniques,which is important for discovering active peptides and analyzing their function.Maize(Zea mays L.),as one of the most important crops in the world,is widely cultivated in more than 150 countries and has made great contributions to the food safety.In recent years,with the demand increasing,the area planted has also increased and keep a high position in agriculture.However,it has been subjected to various stresses during corn growth,such as corn sheath blight,one of the diseases that cause severe reduction in output.Therefore,studying the defense mechanism of corn against Rhizoctonia solani has important significance in preventing and treating.In order to study the change of the peptides in the plant infected with Rhizoctonia solani(R.solani),corn leaves cultivated in different days after inoculated with R.solani were collected as the research material.Quantitative peptidomics was used to screen and identify the peptides that were differentially expressed in response to stress of corn sheath blight.The differentially expressed peptides were then analyzed in order to further elucidate the plant disease resistance mechanism.The results are as follows:1.The change of chlorophyll and nitrogen content in maize leaves:it was found that the levels of chlorophyll and nitrogen in maize leaves decreased with the prolongation of treatment time,indicating that R.solani could damage the transport tissues in stems.When the transportation was blocked,the blade withered with chlorophyll gradually decomposition.2.Three enzymes’ activity,including superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT),were measured.According to the experimental results,we found that these enzymes generally increased at first,then decreased and increased finally.It indicated that the change might be related to the plant existed environment and the degree of its own active oxygen metabolism.The content of malondialdehyde(MDA)was gradually increase in leaves tissue,indicated that the harmful substances produced by plants under stress were gradually accumulated.The reactive oxygen species(ROS)were also detected in maize leaves by DAB and NBT staining methods indicated that ROS was indeed accumulation in maize leaves.3.Based on the result of peptidomics assay,749 peptides belonging to 266 precursor proteins were identified,in which 124 significant changed peptides were found in the treatment group at 3 day,while a total of 141 differentially expressed peptides were found at 7 day,and 33 peptides were changed at both time points.The statistical analysis of the precursor proteins showed that most of the peptides existed in cell membranes,chloroplasts,lysosomes and other organelles.They participated in the metabolism,stress and defense responses of the organism.The function of other peptides need to be further functional verification.This study attempt to explain the molecular mechanism of plant response to stress from the new perspective of peptidomics.The plant peptidomics provides a theoretical basis for the study of plant resistance to pathogen stress.