Reversible phase dynamics of PsAF5 regulate mitophagy to balance redox levels in Phytophthora sojae.

Redox balance is essential for normal cellular functions. PsAF5, a FYVE domain-containing protein, functions as an essential sensor and adapter, particularly in mitophagy triggered by reactive oxygen species in Phytophthora sojae. However, the regulatory role of PsAF5 in maintaining the dynamic equilibrium of the intracellular redox state has not yet been fully elucidated. Here, we identify that specific cysteine residues in the FYVE domain of PsAF5 sense cellular redox states to form and resolve disulfide bonds in a redox-dependent manner. Under reducing conditions, PsAF5 undergoes redox-dependent phase separation to form cytoplasmic condensates that are functionally decoupled from mitophagy execution. Under oxidative conditions, PsAF5 exhibits increased cytosolic solubility and enhanced interaction with PsATG8, thereby promoting mitophagy. This mechanism enables P. sojae to toggle between "detoxification" (oxidizing stress) and "metabolic resilience" (reducing stress) states, ensuring survival across hostile host niches.