Ascospore release and oxylipin production in the yeast Dipodascopsis

Abstract

The genus Dipodascopsis was extensively studied with regards to reproductive cycles as well as the presence, distribution and function of 3-OH oxylipins. Most of this research was carried out on D. uninucleata var. uninucleata (Canadian strain) as well as D. tóthii. However, little is known concerning D. uninucleata var. uninucleata isolated from South African soil, as well as D. uninucleata var. wickerhamii. Consequently, using gas chromatography-mass spectrometry, electron microscopy and confocal laser scanning microscopy, the two varieties were compared regarding their morphologies, oxylipin production, mitochondrial activity as well as life cycles and ascospore release. According to literature, the two varieties differ only in their ability to assimilate certain carbon sources. During this study, differences in ascospore size as well as differences in ascospore clustering, after release, was observed. Furthermore, differences in the type of 3-OH oxylipin produced by the two varieties, also existed. 3-OH oxylipin production was found to be associated mainly with the sexual stage and concentrated in the ascus surrounding the ascospores, in both varieties. Furthermore, increased mitochondrial activity was also observed during the sexual stage and found to be concentrated in close vicinity of the ascospores. Since mitochondria produce 3-OH oxylipins, it is suggested that the increased activity during sexual development would be to aid in the production and release of the ascospores, as well as the accumulation of these 3-OH oxylipins. In addition, acetylsalicylic acid was found to inhibit the production of 3-OH oxylipins by probably decreasing mitochondrial activity resulting in the inhibition of ascospore release.