A chorismate mutase from Radopholus similis plays an essential role in pathogenicity

In the process of infecting plants, plant parasitic nematodes release a series of proteins that play an essential role in the successful infection and pathogenesis of plant cells and tissues through stylets or body walls. In this study,based on transcriptome data, a chorismate mutase gene of Radopholus similis(RsCM) was identified and cloned,which is a single copy gene specifically expressed in the oesophageal gland and highly expressed in juveniles and females. Transient expression of RsCM in tobacco leaves showed that it was localised in the cytoplasm and nucleus of tobacco leaf cells, which inhibited the pattern-triggered immunity(PTI) induced by flg22, including callose deposition and defence gene expression, and cell death induced by immune elicitors BAX, but could not inhibit cell death induced by immune elicitors Gpa2/RBP-1. The RNA interference(RNAi) transgenic tomato of RsCM obviously inhibited the infection, pathogenicity, and reproduction of R. similis. However, the resistance of the overexpression transgenic tomato of RsCM to R. similis infection was significantly reduced, and the expression levels of two salicylic acid(SA) pathway genes(PR1 and PR5) in roots infected by the nematode were significantly down-regulated,which indicated that RsCM might be involved in the inhibition of SA pathway. The results of this study demonstrate that RsCM suppresses the host immune system and might be a new target for the control of R. similis, which also provides new data for the function and mechanism of CM genes of migratory parasitic plant nematodes.

Community Diversity of Associated Bacteria of Radopholus similis

[ Objective ] The paper was to reveal the species abundance of associated bacterial community of Radopholus similis, and the diversity of its bacteria. [Methods] Through the construction of 16S rDNA cloning library of bacteria, the positive clone was carried out ARDRA analysis, and the phylogenetic tree was constructed. [ Results] OUT （ Operational Taxonomic Units） was classified according to sequences similarity of 97%, and the constructed 16S rDNA library of bacteria contained 13 OTUs, belonging to Alphaproteobacteria, Betaproteobacteria and Gammaproteobacterla, respectively. The dominant species was Betaproteobacte- ria, especially Burkholderia was the dominant bacterium. [Condusions] The diversity of associated bacteria of R. similis was high, and these bacteria may have certain ecological significance to R. similis.

Study on burrowing nematode, Radopholus similis, pathogenicity test system in tobacco as host

Radopholus similis(Cobb 1893) Thorne(1949) is a destructive migratory endoparasitic plant nematode. In this study,the pathogenic process of R. similis infection in Nicotiana benthamiana(tobacco) was studied using quartz sand culture in laboratory. The results showed that R. similis mainly parasitised the root cortex, leading to cortical cell decomposition and tissue decay. We optimised the inoculation conditions to establish a method for determining the pathogenicity of R. similis as follows:(1) a glass culture tube was filled with quartz sand(about 1/3 of the height) and sterilised twice;(2) 20-day-old N. benthamiana seedlings were transplanted into test tubes and cultivated for 10 days at(25±1)°C;(3) R. similis female nematodes were inoculated in the root rhizosphere at a rate of 150 nematodes per plant;(4) the number of nematodes, disease severity, and growth of the plant at 30 days post-inoculation(dpi) were determined. The pathogenicity of eight R. similis populations from different hosts was determined, which proved the feasibility of this method.