| Summary: | <i>Fusarium oxysporum</i> f. sp. <i>cubense</i> (<i>Foc</i>), which causes Fusarium wilt of bananas, is considered one of the most destructive fungal pathogens of banana crops worldwide. During infection, <i>Foc</i> secretes many different proteins which promote its colonization of plant tissues. Although <i>F. oxysporum</i> has no sexual cycle, it has been reported to secrete an α-pheromone, which acts as a growth regulator, chemoattractant, and quorum-sensing signaling molecule; and to encode a putative protein with the hallmarks of fungal α-pheromone precursors. In this study, we identified an ortholog of the α-pheromone precursor gene, <i>Foc4-PP1</i>, in <i>Foc</i> tropical race 4 (TR4), and showed that it was necessary for the growth and virulence of <i>Foc</i> TR4. <i>Foc4-PP1</i> deletion from the <i>Foc</i> TR4 genome resulted in decreased fungal growth, increased sensitivity to oxidative stress and cell-wall-damaging agents, and attenuation of pathogen virulence towards banana plantlets. Subcellular localization analysis revealed that Foc4-PP1 was concentrated in the nuclei and cytoplasm of <i>Nicotiana benthamiana</i> cells, where it could suppress BAX-induced programmed cell death. In conclusion, these findings suggest that Foc4-PP1 contributes to <i>Foc</i> TR4 virulence by promoting hyphal growth and abiotic stress resistance and inhibiting the immune defense responses of host plants.
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