Screening Of Maize Peptides Related To AM Fungi Symbiosis Based On The Quantitative Peptideomics

Arbuscular Mycorrhizal fungi(AMF)can form a mutualistic relationship with 80%of terrestrial plants.Maize not only is an important food and industrial crop of the world,but also is an important host of AMF.Previous studies showed that AMF can improve the nutritional status of host plants,increase the absorption mineral nutrients and water,and enhance the ability of plants to stress and diseases resistance.Currently,the symbiotic mechanism of interaction between plant and microorganism mostly is analyzed by genomics and proteomics.However,the function of peptideomics in the vivo is hardly known.Some secreted peptides of plants are key in controlling intercellular communication during plant development.As molecular messengers,these secreted peptides participate signal communication,when plants interact with other organisms.But some factors restrict the discovery and functional analysis of plant peptideomics such as the high complexity and low abundance of peptides,the low resolution of separation techniques and the poor resolution of mass spectrometer.In this study,high resolution grade chromatography-mass spectrometry was used to analyze the peptides of B73 maize inoculated with AMF at different time periods.These peptides were further analyzed by NanoLC-MS/MS.The peptideomics data were compared against the UniProtKB and NCBI databases.The changes of discrepancy peptides in maize roots inoculated with AMF were quantitated.By analyzing the peptideomics data at different time points of AM inoculation,the peptides fragments related to plant symbiosis were screened.It will lay a foundation for further research on the functions of genes and proteins.The main results are as followed:1·In the light of One-way analysis of variance,the phenotypes of maize roots inoculated with AMF at different time periods were analyzed.We found that AMF promotes lateral root growth of maize,but there are no obvious difference of plant height and root length.2.After 10 days of AM inoculation,about 3%of the hyphae infected the roots,but no symbionts were formed.The infection rate was about 30%at 20 days.Under the microscope,some extracrhizal hyphae invaded into the root cells of maize and formed arbuscule and vesicle structures.At 30 days,the infection rate reached 44%,the arbuscular structure increased significantly,and new hyphae and spores were produced.3.After maize roots treated with AMF,we identified a total of 674 peptides from 239 precursor proteins at 10 days,603 peptides from 194 precursor proteins at 20 days,and 419 peptides from 173 precursor proteins at 30 days.4.By comparing the polypeptide sequences at different periods,we found that there were 237 overlapped peptides between 10 and 20 days,153 overlapped peptides between 10 and 30 days,and 178 overlapped peptides between 20 and 30 days.There were 104 overlapped peptides fragments among three time periods.The increase of VGYGVEDGVPYWLIK peptide was detected from 10 to 20 days,and decrease until 30 days.The AFDNKYYFDLIAKQ peptide shows a down-regulated tendency at 10 day,and an up-regulated level was exhibited at 30 day.The GGPVDPSKLVVELGPM peptide did not change from 10 to 20 days and up-regulated significantly at 30 days.5.By screening the corresponding protein precursors of the polypeptides with significant differences at different time points,we found that most of the peptides were located in the middle of the precursor proteins,and the subcellular localization was shown in the vacuoles.Their biological processes were mainly involved in plant metabolism and stress response.The molecular function mainly focused on binding molecule activity,cysteine peptidase activity,peroxidase activity and peptidase activity.The breaking points in the corresponding protein precursors of significantly different peptides were often demonstrated in the amino acid sites of Ala,Gly,Leu and Lys.6.After synthesis of GYGVEDGVPYWLIK and AFDNKYYF DLIAKQ,the different concentration gradients of two peptides were used to analyze their effects on the growth of maize.However,their functional characteristics should be further studied in the future.The differentially identified peptides provide research contents for further study on the function of specific peptide participating the regulation of AMF.The research results will enrich the theoretical knowledge of interaction between plants and microorganisms,and provide a reference for peptide function during symbiosis.