The key gluconeogenic gene <i>PCK1</i> is crucial for virulence of <i>Botrytis cinerea</i> via initiating its conidial germination and host penetration

The process of initiation of host invasion and survival of some foliar phytopathogenic fungi in the absence of external nutrients on host leaf surfaces remains obscure. Here, we demonstrate that gluconeogenesis plays an important role in the process and nutrient-starvation adaptation before the pathogen host invasion. Deletion of phosphoenolpyruvate carboxykinase gene BcPCK1 in gluconeogenesis in Botrytis cinerea, the causative agent of grey mould, resulted in the failure of the ΔBcpck1 mutant conidia to germinate on hard and hydrophobic surface and penetrate host cells in the absence of glucose, reduction in conidiation and slow conidium germination in a nutrient-rich medium. The wild-type and ΔBcpck1 conidia germinate similarly in the presence of glucose (higher concentration) as the sole carbon source. Conidial glucose-content should reach a threshold level to initiate germination and host penetration. Infection structure formation by the mutants displayed a glucose-dependent fashion, which corresponded to the mutant virulence reduction. Exogenous glucose or complementation of BcPCK1 completely rescued all the developmental and virulence defects of the mutants. Our findings demonstrate that BcPCK1 plays a crucial role in B. cinerea pathogenic growth and virulence, and provide new insights into gluconeogenesis mediating pathogenesis of plant fungal pathogens via initiation of conidial germination and host penetration.

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