| Elicitors were pathogen signal molecules which were recognized by the host, they were important signal molecules for pathogen and plant to identify each other. Elicitors could induce gene expression and host plant defense responses, such as the generation of reactive oxygen species, deposition of callose and hypersensitivity reactions etc. These signal molecules caused to induce plants local resistance or resistance system to prevent the spread of the pathogen and the secondary infection. Switched signal between pathogen and plant leads to plant disease or disease resistance eventually. Our research object was Xanthomonas oryzae pw.oryzae PXO99A, we predicted and verified novel elicitors which made us further understand the interactions between pathogenic bacteria and plant and their evolutionary relationships.Elicitors were mainly secreted by type Ⅲ secretion system in Xanthomonas, which were characterized by about 100 bases there was a conservative cis regulatory elements PIP (plant-inducible promoter) box upstream the gene sequence and n-terminal amino acid composition more conservative. We predicted elicitors in PXO99A genome through Effective T3, SIEVE and BPBAac projections and selected 24 genes with unknown function as the research object which were the intersection of two or three forecasting software; we independently predict elicitors according to the gene sequence upstream PIP box and got seven potential elicitors with unknown function. Besides type Ⅲ secretion system elicitors, other secretion system had been reported elicitors, we got eight exocytosis protein through PSORTdb. We transient expressed 39 potential elicitor gene mediated by Agrobacterium tumefaciens in Nicotiana benthamiana and detected plant PTI related phenotypes such as reactive oxygen species, calluses deposition and high expression of PTI marker gene to verified the functions of genes. The results showed that in 39 genes there were eight genes were elicitors, nine genes were potential elicitors and one gene was not an elicitor. In addition, based on plants phenotypic we selected 15 genes to do gene knockout and got 18 PXO99A mutants, but we hadn’t got the pathogenic changes of 18 knockout mutants on rice due to the season and limited time.Bacillus thuringiensis was a kind of gram-positive bacteria which was insect pathogenic and widely existed in soil. We found a protein which could induce plant to produce necrosis, ethylene in the YBT-1520 and named it NEL. Through bioinformatics analysis, NEL was consist of nppl (necrosis-inducing phytophthora protein) domain and Ricin B domain. We transient expressed npp1 mediated by Agrobacterium tumefaciens in Nicotiana benthamiana and detected plant PTI related phenotypes such as reactive oxygen species, calluses deposition and high expression of PTI marker gene to verified the functions of function of npp1 in plants. We purified Ricin B protein, tested the protein with blood cell agglutinate and confirmed Ricin was lectin. C. elegans N2 and glycolipids mutants bre-5 was used to verified the function of NEL, the activity of growth inhibition of NEL was higher than either npp1 or Ricin, Glycolipids mutants bre-5 have resistance to NEL. Npp1 was perforated toxin and similar to the function of cry protein in bacillus, therefore NEL provides a new perspective for the origin of insecticidal crystal protein in Bacillus thuringiensis. |
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