| Hydroxyproline-rich glycoproteins (HRGPs) are mainly structural proteins found inthe cell walls of most advanced plants. The accumulation of HRGPs in host plant cell wallsupon wounding and pathogen attack is relative to disease resistance of plants.Arabinogalactan proteins (AGPs) are a class of HRGPs. Previous studies have shown thatAGPs may take part in plant defense responses. However, specific roles of individualHRGPs in plant defense against pathogen are poorly understood. Therefore, it is necessaryand important to investigate the resistance mechanism of HRGPs, which plays theoreticaland praetical roles in the research of study on plant-pathogen interaction.In this study, two wax gourd (Benincasa hispida Cogn.) lines (fusarium wilt resistantand susceptible, respectively) was used as the material to investigate their inducibleregulation and subcellular localization after being inoculated with Fusarium oxysporum f.sp. Benincasae. The main results were as follows:1. We analyzed the expression characteristics of HRGPs during the interactionbetween wax gourd and Fusarium oxysporum using immunogold labelling technique andmonoclonal antibodies in situ. The results showed that HRGPs mainly located in the hostcell wall and intercelluar space. The epitope levels of JIM11, JIM20and MAC204antibodies in resistant cultivar were higher than in susceptible cultivar. These resultsindicate that HRGPs were directly involved in the resistance of wax gourd to Fusariumthrough interfereing with the infection of the pathogen.2. The effects of immunomodulaiton with antibodies recognizing HRGPs (JIM11,JIM20and MAC204antibodies) and HRGPs inhibitors on the growth of radicles of waxgourd were investigated. The results showed that the length of the radicle were promotedby the treatments with JIM11、JIM20and MAC204antibodies as well as200μM3,4-DHP(biosynthesis inhibitor of extensin)and20μg·ml-1Gum arabic (exogenous AGPs) atdifferent degrees. Of which, the effect of20μg·ml-1Gum arabic was the most remarkable.The treatment with100μM β-Yariv reagent (AGPs precipitator) produced a significantinhibitory effect on the length of the radicles, indicating that β-Yariv reagent inhibited thegrowth of radicles through affecting the expression or function of AGPs. These resultssuggested that high levels of AGPs are good for radicle growth of wax gourd.3. The effect of HRGP regulation on the resistance of wax gourd to Fusarium wilt.Experiment carried out in the laboratory. The expression levels of different HRGPs inthe cell walls of wax gourd after regulation of HRGP and infection of pathogen usingimmunofluorescence technique. The results showed that the JIM11, JIM20and the MAC204antibody-labeled fluorescences were stronger in the resistant cultivar whencompared to the susceptible one both before and after pathogen inoculation. In additionalthe expression levels of the antigens increased in both infected resistant and susceptiblelines after HRGP regulation with MAC204antibodies as well as200μM3,4-DHP. Theseindicate that the increase in HRGPs expression levels is closely related to the resistance ofwax gourd to Fusarium. HRGPs content can be used as an important physiologicindex/parameter of plant disease resistance mechanism. However, treatment with100μMβ-Yariv reagent resulted in much weaker signal of fluorescence, which may be due to thesuppression of AGPs expression levels by β-Yariv reagent.Field trials. The results showed that treatments with MAC204antibodies and200μM3,4-DHP, could improve greatly the growth potential of the wax gourd seedlings. Thetreated seedlings grew much better than the controls. Moreover, the treated plants alsoshowed higher resistance to the pathogen. |
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