Prediction and functional analysis of AM2As whole genome secretory proteins of Lasiodiplodia theobromae

【Objective】The purpose of the study was to predict and analyze the whole-genome encoded secretory proteins of Lasiodiplodia theobromae AM2As whole genome,and to provide theoretical references for the excavation of key disease-causing genes of this pathogen as well as disease-resistance genes of cocoa.【Method】According to the whole genome sequence of L. theobromae published in NCBI database,SignalP 5.0,ProtComp 9.0,TMHMM 2.0,GPI-SOM, LiPop 1.0 and other bioinformatics software were used for prediction screening and functional analysis of L. theobromae secretory protein sequences. In addition,based on the similarity of protein sequences,PHI,COG and eggNOG-mapper 5.0 database were applied for functional annotation analysis,and then MEGA X,GSDS 2.0,and TBtools 1.09 were used to analyze the phylogenetic evolution of the secretory proteomes and their gene structures and promoter cis-acting elements.【Result】L. theobromae whole genome encoded a total of 13054 proteins,including 638 proteins with potentially typical secretory protein characteristics,accounting for 4.89% of the total. The number of amino acids in the 638 secretory proteins ranged from 55 to 1777,with the majority having 100 to 400 amino acids,accounting for 53.76% of the total number of secretory protein sequences. This indicated that most of the secretory proteins were small proteins. There was a significant difference in the number and percentage of the 20 types of amino acids in the 638 secretory proteins, with Ala having the highest percentage and the percentage of the other types of amino acids not exceeding 10.00%. The number of signal peptide amino acids in the 638 secretory proteins ranged from 15 to 38,with 409 secretory proteins having a signal peptide amino acid number of 17 to 20. The nonpolar amino acid Ala had the highest percentage,while Asp and Glu,with electric side chains,had the lowest percentage. Amino acids in signal peptide-3 and-1 positions were relatively conservative,and the cleavage site belonged to A-X-A type,which could be recognized and cut by Sp I type signal peptide enzyme. The 638 secretory proteins were divided into seven groups,and the members of different groups showed significant differences in protein structures,functions and their conserved motifs. The functional annotations of 400 secretory proteins were obtained,mainly related to carbohydrate transport and metabolic process,protein post-translational modification,amino acid metabolism and transport process. A total of 221 CAZymes and 244 effector proteins were predicted in the secretory proteome,of which 48 effector proteins could be functionally annotated by PHI database.【Conclusion】The functions of the secretory proteins of L. theobromae are mainly concentrated in the processes of carbohydrate transport,metabolism,post-translational modification and amino acid metabolism and transport,as well as other unknown functions and potential pathogenic function. It is preliminarily inferred that during the infection and pathogenesis process,L. theobromae AM2As are regulated by cis-acting elements such as abscisic acid reaction,auxin,lowtemperature anaerobic and light reaction. By secreting a large number of proteins involved in the degradation,metabolism and transport of carbohydrates,it establishes a parasitic relationship,and then uses the metabolic products to help itself accelerate the infection,achieving the effect of pathogenesis.