PacC mediates spatial regulation of the phospholipid metabolism in the apple fruit-Penicillium expansum interaction

Abstract

As a core component of the Pal/Rim-pH signaling pathway in pathogenic fungi, the transcription factor PacC induces the partial acidification of host tissues and modulates the activity of extracellular fungal enzymes. However, the spatial regulation of PacC on phospholipase activity in fruit has not been reported. In this study, the role of the PePacC in Penicillium expansum was investigated by analyzing pH, phospholipid metabolism, cell membrane permeability, and malondialdehyde (MDA) levels in different tissues of apple fruit inoculated with a PePacC-deficient strain of P. expansum (ΔPePacC). The results showed that the pathogenicity and acidification ability were impaired when PePacC was deleted in P. expansum. Compared to the WT inoculation, deletion of PePacC spatially and dynamically regulated the activities of phospholipase A1 (PLA1), PLA2, PLC, and PLD, and the levels of phosphatidylcholine (PC), inositol 1, 4, 5-trisphosphate (IP3), phosphatidylinositol 4, 5-bisphosphate (PIP2), phosphatidylinositol (PI), and phosphatidic acid (PA), and altered the extent of damage to the cell membrane integrity at and outside of the junction of the leading edge of decay in apple fruit during P. expansum infection. Taken together, the present study showed that PacC could mediate the acidifying ability of P. expansum to colonize host fruit, and dynamically regulate the spatial changes of phospholipid metabolism in different apple tissues. Furthermore, both host defense responses and pathogen virulence mechanisms are involved in the apples-P. expansum interaction.