Preliminary Investigations On Interactions Of Watermelon With Fusarium Oxysporum F.sp. Niveum In Histology And Transcriptomics

Watermelon (Citrulls lanatus ) is one of the most important fruit crops in the world and accounts for 20% of the world’s total area devoted to vegetable production(FAO,2007). Fusarium wilt of watermelon, caused by soil-borne fungus Fusarium oxysporum f. sp. niveum (E. F. Smith) Snyder & Hansen (FON), is one of the most severe vascular diseases worldwide. The disease is a yield-limiting factor in watermelon production and occurs at all growing stages of watermelon. During the long processes of host-pathogen co-evolution, plants have developed various elaborate mechanisms to ward off pathogen attack. So understand interactions mechanism between plants and pathogens that might provide insight into the elucidating genetic basis of watermelon defense against pathogens. As far as we are aware, this study presents the first molecular characterization of FON–host interactions. The FON-regulated genes identified in this study could help us better understand the infection process and assist efforts to develop FON-resistant watermelon. This information is of general interest and may aid the development of rational strategies for managing Fusarium wilt disease in watermelon.In this paper, confocal imaging of F. oxysporum f. sp. niveum infection of watermelon roots revealed histological characteristic interactions by green fluorescent protein-tagged. We constructed a suppression subtracted and normalized cDNA library representing different stages of a incompatible interaction between watermelon and Fusarium oxysporum and then identified 1756 EST-unigenes for watermelon. On the basis of EST-unigenes, we employed Agilent’s custom Gene Expression Microarrays by an ink-jet oligonucleotide synthesizer and quantitative Real-Time PCR method to investigate gene expression changes in watermelon, at different time points during a resistant interaction with F. oxysporum f. sp. niveum.Confocal imaging revealed that colonization and infection of watermelon root by green fluorescent protein-tagged isolate of Fusarium oxysporum f. sp. niveurn. It was described as following (i) the transformation of F. oxysporum f. sp. niveurn with a plasmid-harboring gfp that results in stable expression of gfp, (ii) the demonstration that GFP is an excellent reporter in Fusarium oxysporum f. sp. niveurn for visualizing by confocal laser scanning microscopy (CLSM) its behavior in the watermelon rhizosphere under in vivo conditions. And (iii) novel aspects of the colonization and infection processes on watermelon roots by F. oxysporum f. sp. niveurn. (iiii)Few differences in the initial infection and colonization of roots were observed between resist.Using the PCR-Select cDNA Subtraction Kit protocol, a SSH-cDNA library of the watermelon root tissues induced by Fusarium oxysporum f.sp.niveurn was constructed。The positive clones of the cDNA library were sequenced randomly and 3895 desired ESTs were obtained for bioinformatics analysis. Totally 1756 unique sequences were annotated for the functions. Many expressing genes such as transcription factors、Protein kinase、defence gene、shikimate-phenylpropanoid-lignin metabolism and JA biosynthesis were found in the incompatible interaction between watermelon and Fusarium oxysporum. 36.3% of the annotated unique sequences had similar function with disease resistance and defense. This information showed us an elementary profile of the interaction mechanism between watermelon and Fusarium oxysporum and could develop a good foundation for the further exploration in that interaction mechanism at the molecular level and the related important genes cloning.To obtain an overall picture of the interaction between watermelon and Fusarium oxysporum, a microarrary analysis was performed, using Agilent’s Custom Gene Expression Microarrays, representing approximately 8,000 genes. The results showed that 679 genes were up-regulated while 708 genes down-regulated; more than two times fold in inoculation watermelon root as compared with the control. Studies of expression patterns of these genes provided new information on the incompatible interaction between watermelon and Fusarium oxysporum, including induction of pathogenesis-related genes, transcription factor, signaling/regulatory gene, and cell wall modification. The transportation proteins, such as aquaporins and high affinity potassium transporter might be specific to vascular wilt diseases. Several gene homologues associated with the JA signaling pathway and lignin pathway were differentially expressed in infected tissues. These suggested that JA and lignin involved in inhibiting Fusarium oxyspporum f.sp niveum colonization in wtermelon. Results of quantitative real-time PCR in incompatible and compatible interaction also supported this case.In addition, based on the genome sequence of Citrullus lanatus (Thunb.) and resequencing 16 domesticated and wild watermelon , ClMYB and ClPR5 which were gained by EST assemble were compared the sequencing of the watermelon genome and identified single-nucleotide polymorphisms in resequencing of watermelon , ClPR5 gene has no single-nucleotide polymorphisms in resistant and susceptible watermelon cultivars. ClMYB gene has a single-nucleotide polymorphisms in resistant and susceptible watermelon cultivars, but would be validated in more resistant and susceptible watermelon cultivars.The paper investigated during Interactions of watermelon with Fusarium oxysporum f.sp. niveum on histology and transcriptomics, based on the genome sequence of watermelon, ClMYB and ClPR5 genes were analysis.