| Summary: | 碩士 === 國立中興大學 === 植物病理學系所 === 107 === Fusarium oxysporum f. sp. niveum (Fon) is one of the limiting factors for watermelon production, which causes dramatic economic loss. Uncovering the molecular defense mechanisms of watermelon against Fon provides new insight in controlling watermelon Fusarium wilt. Differentially expressed genes (DEGs) related to watermelon hormone pathways were obtained from transcriptome profiling of watermelon-Fon interaction in previous studies. In this research, expression of these hormone pathway-related genes was analyzed by real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) to understand hormone regulation events in the shoot base of Fon-resistant (JSB) and Fon-susceptible (Sugar Baby, SB) watermelon lines during early infection (0-3 days post inoculation) with Fon. The results suggest that salicylic acid pathway and ethylene pathway might not involve in the defense response during early infection of Fon at watermelon shoot base. Meanwhile, jasmonate (JA) biosynthesis pathway was significantly activated in the Fon-susceptible line SB, especially at 3 days post inoculation (dpi). Activating JA signaling pathway triggers JA-dependent defense responses. However, over-activated defense responses may promote senescence thus increase the susceptibility of watermelon. Other than hormone pathway-related genes, expression of the pathogenesis-related protein 5 (PR-5 protein) genes, thaumatin-like protein genes (TLPs), was significantly higher in JSB than in SB at 1 dpi and 2 dpi. It suggested that induction of watermelon TLP at proper time may involve in JSB resistance against Fon. The watermelon TLP (ClTLP, encoded by Cla001150) has a conserved acidic cleft, which is the structure related to antifungal activity. We therefore expressed the recombinant ClTLP for further examination of its antifungal activity. However, the formation of insoluble inclusion bodies of ClTLP in Escherichia coli needs to be overcome. This research provides molecular insights of the early events of watermelon-Fon interaction, which gives eligible candidates for future application on the breeding of Fon-resistant watermelon lines.
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