Abstract: The fungal pathogen Fusarium oxysporum f. sp. niveum（Fon）that causes Fusarium wilt in watermelon is a soilborne fungus. During interactions between F. oxysporum and host plant，the fungus secretes several effector proteins into the plant xylem to promote virulence. These effectors are small cysteine-rich proteins and are called SIX（Secreted in Xylem）proteins. Among them，the SIX6 was proved to be a virulence factor. To understand function and signaling pathway of FonSIX6 in watermelon，FonSIX6 was cloned from Fon. To construct the bait vector pGBKT7-SIX6 for yeast two-hybrid，the encoding region of FonSIX6 was fused to the GAL4 DNA-binding domain in yeast expression vector pGBKT7. Then bait vector was transformed into Y2H gold strain. Transcriptional activation and toxicity test showed that the bait could be used in yeast two hybrid screens. PI296341-FR，a watermelon line that was resistant to all Fon races was used to construct the cDNA expression library in yeast cells.Byyeast two hybrid screens，14 interacting proteins were identified that interact with FonSIX6. These proteins involved in various pathways such as energy metabolism，photosynthesis and regulation of gene expression. According to our results，FonSIX6 may target the host energy and photosynthesis system to promote virulence，while host regulated resistant gene expression response to FonSIX6.

Key words:  watermelon, fusarium wilt, effector protein, yeast two hybrid