| Harpin is an elicitor which encoded by the hrp (hypersensitive response and pathogenicity) gene and elicite plants to produce a series of defense responses as reactive oxygen species (ROS) and hypersensitive response in non-host plants. Harpinxoo encoded by hrp (hpalxoo) gene coming from Xanthomonas oryzae can induce tobacco to resist TMV and tomato to resist Botrytis cinerea.Transgenic hpalxoo plants such as pears, tobacco, rice and cotton can resist to a variety of diseases. Harpinxm was found in cotton bacteria blight pathogen Xanthomonas campestris. It has the similar characters as most Harpins. However, the reactive oxygen species accumulation process, related gene expression and biological effects of Harpinxoo and Harpinxm are not clear so far.In order to understand the mechanism of Harpinxoo and Harpinxm, and to explore the possibility of their practical application, this review using tobacco as a model plant, has observed and measured H2O2accumulation in tobacco leaf tissue ecilited by Harpinxoo and Harpinxm-The same time, this study have determined and analised the expression of related genes, observed and determined the effect of Harpinxoo and Harpinxm for controlling rubber powdery mildew. Furthermore, this study has prepared Harpinxoo and Harpinxm nanoparticles to the product. The primary results of the dissertation are summarized as follows:1. H2O2content is determined in tobacco leaf tissue at different times after ecilited by Harpinxoo and Harpinxm. The results showed that H2O2content significantly increased within12hours. Both Harpinxoo and Harpinxm can ecilit two peaks of H2O2content in tobacco leaves, the peaks of Harpinxoo elicited appearing in the treatment of1h and9h, and the peaks of Harpinxm elicited appearing in the treatment of0.5h and9h.2. The expression of hypersensitive response marker gene(hsr203J and hin1), reactive oxygen species metabolism gene (rboh), and alternative oxidase gene(aoxl) are detected at different time after elicited by Harpinxoo in the tobacco leaf tissue. The result shows that hsr203J sustain significantly expressed from0to12hours, hinl as the time of appearance of H2O2content peaks performs obviously expression meanwhile, and rboh gene and aoxl gene have different levels of expression in the0-12h. The same treatment and detection of Harpinxm, hsr203j and hinl appears at the time of H2O2content peaks, while, the rboh gene gradually weakened with the extension of elicited time.In the view of above, Harpinxoo and Harpinxm are initiated by eciliting oxidative burst to start such as hsr203j, rboh, hin1and aox1genes expression, and then ecilit hypersensitive response.3. HarpinXoo and HarpinXm as an active ingredient are prepared to nanoparticles respectively with chitosan as carrier. Per milliliter HarpinXoo (or HarpinXm) solution (100μg/mL) can be prepared to HarpinXoo (or HarpinXm) nanoparticle solution10milliliter, and the effective concentration is10μg/mL. They are the same as HarpinXoo and HarpinXm who can induct hypersensitive response in tobacco leaves, palying a significant role in growth with effect of94.7%and104.5%respectively.4. After the rubber tree leave was inoculated Oidium heveae Steinmann spores, the generation and extention of powdery mildew scab is observed, and the microscopic examination of Oidium heveae Steinmann spore differentiation was produced with spraying HarpinXoo or HarpinXm on rubber tree leaves. The result shows that spores of Oidium heveae Steinmann on the rubber tree leave can not germinate normally after rubber tree leave were treated by HarpinXoo or HarpinXm. The spores can not differentiate haustoria and primary hyphae, ultimately unable to complete the infection process in the leave. These results indicate that HarpinXoo and HarpinXm can inhibit the propagation and infection of Oidium heveae Steinmann on rubber tree leave, have application prospects for controlling rubber powdery mildew. |
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