| Peach(Prunus persica)gummosis is one of the main diseases of peach tree worldwide,and it is particularly serious in the peach industry throught southern China.There is no effective control method in the production at present.Effectors play a crucial role in the interaction between pathogen and host plants.Therefore,it is of great significance to carry out the research on the effectors to understand the pathogenic mechanism and control effectively of gummosis.It was reported that the main pathogenic fungi of peach gummosis were Botryosphaeria spp.Among them,Lasiodiplodia theobromae had strong pathogenicity and could cause rapid gummy flow in perennial branches.Botryosphaeria dothidea is widely distributed,but has relatively weak pathogenicity.In this study,two strains of pathogenic fungi L.theobromae JMB122 and B.dothidea XNHG241 were selected as materials.Firstly,Lt17 with strong toxicity was successfully screened out according to the candidate effectors in the genome of L.theobromae JMB122,and its function was further studied.In addition,this study revealed the whole genome characteristics of B.dothidea XNHG241 through genomic analysis,which provided theoretical basis for the study of its pathogenesis.The main results obtained from this study are as follows:1.Screening and identification of JMB122 effectors of L.theobromae strain.The candidate effector protein Lt17 suppressed programmed cell death induced by BAX or INF1 in Nicotiana benthamiana.The sequence characteristic analysis of the effector Lt17 showed that it had N-terminal signal peptide region and did not contain transmembrane domain.qRT-PCR analysis showed that Lt17 gene expression significantly increased after JMB122 infection in peach branches.The fusion protein of effector Lt17 and green fluorescent protein GFP was transformed into tobacco,and it was found to be located in the apoplast.The results showed that Lt17 was consistent with the characteristics of the effector.2.Functional study of effector Lt17.Transient expression of Lt17 in tobacco leaves was found to inhibit flg22-induced ROS accumulation and callose deposition.The secretory system of p SUC2 yeast and TTC tests showed that the signal peptide had secretory functions.Overexpression of Lt17 in N.benthamiana leaves and P.persica leaves increased the susceptibility of the plants to Phytophthora capsici and L.theobromae.The knockout mutant of Lt17 was obtained by homologous recombination,and it was found that Lt17 contributed to the growth and development of L.theobromae.And the deletion of Lt17 led to significant reductions in virulence on peach branches compared with wild type.These results indicated that Lt17 was involved in the pathogenic process of L.theobromae.3.Whole genome sequencing analysis of B.dothidea strain XNHG241.The whole genome of XNHG241 was sequenced using high-throughput sequencing technology.The results indicated that the genome size of XNHG241 was 48.19 Mb,the genome coverage was about 100 X,the GC content was 54.22%,and 52 contigs were assembled.A total of 1354 pathogene-host interaction genes and 446 virulence genes were identified by genome prediction and annotation,and 866 secretory proteins,234 P450 genes and 551 secondary metabolic genes were predicted,respectively.Using comparative genomic analysis,we analyzed the basic characteristics of the genomes of15 B.dothidea strains,and found that the genome sizes of strain XNHG241 and other15 reported strains range from 43.50 to 51.76 Mb.In addition,the collinearity of XNHG241,BDLA16-7 and sdau11-99 is analyzed,and it is found that XNHG241 showed higher homology with the strain sdau11-99 than with the strain BDLA16-7.And the variation among organelle genomes was analyzed,including SNP,InDel and SV analysis.It was found that XNHG241 and BDLA16-7 had more InDel and SV,and XNHG241 and sdau11-99 had more SNPs mutants. |
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