Oxylipins in the yeast genus Ascoidea

English: Acetylsalicylic acid (ASA)-sensitive 3-hydroxy (3-OH) oxylipins were uncovered in 1991 in the yeast Dipodascopsis uninucleata. Since then, various similar oxylipins were found to be widely distributed in fungi. Interestingly, 3-OH oxylipins were reported to play a role in ascospore release from enclosed asci, where they are involved in assisting nano-scale gear-like (D. uninucleata); sliding (Dipodascus); drilling (Eremothecium sinecaudum) and piercing movements (E. ashbyi and E. coryli). In Ascoidea africana, a 3- OH 10:1 oxylipin was found to be associated with hat-shaped ascospores carried inside ellipsoidal asci. However, in this study no function was proposed for this oxylipin. Since only one species representing the genus Ascoidea was studied, it became the aim to further expand this study to also include A. corymbosa and A. rubescens. Using confocal laser scanning microscopy (CLSM) on cells stained with fluorescein-coupled 3-OH oxylipin specific antibodies, this study suggests that oxylipins are specifically associated with ascospores and not vegetative cells of A. corymbosa and A. rubescens. Using gas chromatography - mass spectrometry (GC-MS) the oxylipin, 3-OH 17:0, was identified in A. corymbosa. Here, oxylipin-coated razor sharp ascospore brims may play a role in rupturing the ascus to affect forced release of hat-shaped ascospores. Literature suggests that 3-OH oxylipins are produced by β-oxidation or fatty acid synthesis in mitochondria of yeasts. Since these oxylipins accumulate in sexual cells (asci), increased mitochondrial activity is therefore expected in these structures. Strikingly, this assumption is supported in this study. Using selective fluorescence mitochondrial staining and CLSM, evidence is provided that mitochondrial function is much higher in asci containing increased amounts of 3-OH oxylipins compared to the corresponding asexual vegetative cells. Furthermore, when ASA, a mitochondrial inhibitor, was added in increased concentrations to cultures of Ascoidea, the sexual stage was found to be more sensitive. Ascospore liberation from asci was first inhibited followed by asci formation while some vegetative growth could still be observed.