Mitochondrial β‐oxidation regulates organellar integrity and is necessary for conidial germination and invasive growth in M agnaporthe oryzae

Fatty acids stored as triglycerides, an important source of cellular energy, are catabolized through β‐oxidation pathways predicted to occur both in peroxisomes and mitochondria in filamentous fungi. Here, we characterize the function of E noyl‐ CoA hydratase Ech1 , a mitochondrial β‐oxidation enzyme, in the model phytopathogen M agnaporthe oryzae . Ech1 was found to be essential for conidial germination and viability of older hyphae. Unlike wild‐type M agnaporthe , the ech1 Δ failed to utilize C 14 fatty acid and was partially impeded in growth on C 16 and C 18 fatty acids. Surprisingly, loss of β‐oxidation led to significantly altered mitochondrial morphology and integrity with ech1 Δ showing predominantly vesicular/punctate mitochondria in contrast to the fused tubular network in wild‐type M agnaporthe . The ech1 Δ appressoria were aberrant and displayed reduced melanization. Importantly, we show that the significantly reduced ability of ech1 Δ to penetrate the host and establish therein is a direct consequence of enhanced sensitivity of the mutant to oxidative stress, as the defects could be remarkably reversed through exogenous antioxidants. Overall, our comparative analyses reveal that peroxisomal lipid catabolism is essential for appressorial function of host penetration, whereas mitochondrial β‐oxidation primarily contributes to conidial viability and maintenance of redox homeostasis during host colonization by M agnaporthe .