Abstract
The coexistence of sexual and asexual reproductive cycles within the same individual is a striking phenomenon in numerous fungi. In the fungus Aspergillus nidulans (teleomorph: Emericella nidulans) endogenous oxylipins, called psi factor, serve as hormone-like signals that modulate the timing and balance between sexual and asexual spore development. Here, we report the identification of A. nidulans ppoA, encoding a putative fatty acid dioxygenase, involved in the biosynthesis of the linoleic acid derived oxylipin psiBalpha. PpoA is required for balancing anamorph and teleomorph development. Deletion of ppoA significantly reduced the level of psiBalpha and increased the ratio of asexual to sexual spore numbers 4-fold. In contrast, forced expression of ppoA resulted in elevated levels of psiBalpha and decreased the ratio of asexual to sexual spore numbers 6-fold. ppoA expression is mediated by two developmental regulators, VeA and the COP9 signalosome, such that ppoA transcript levels are correlated with the initiation of asexual and sexual fruiting body formation. PpoA localizes in lipid bodies in these tissues. These data support an important role for oxylipins in integrating mitotic and meiotic spore development.
Highlights
A unique property of many fungi is their ability to propagate by both sexual and asexual spores
Forced expression of ppoA resulted in elevated levels of psiB␣ and decreased the ratio of asexual to sexual spore numbers 6-fold. ppoA expression is mediated by two developmental regulators, VeA and the COP9 signalosome, such that ppoA transcript levels are correlated with the initiation of asexual and sexual fruiting body formation
The A. nidulans asexual reproductive cycle can be divided into at least three different stages: (i) a growth phase required for cells to acquire the ability to respond to induction signals, (ii) initiation of the developmental pathway, and (iii) execution of the developmentally regulated events leading to sporulation
Summary
Strains were grown on glucose minimum medium (GMM) [11] with appropriate supplements for the corresponding auxotrophies, at 37 °C in continuous dark or in continuous white light. Developmental cultures were grown on GMM, and asexual and sexual induction was performed as previously described [4]. Sexual crosses of A. nidulans strains were conducted according to Pontecorvo et al [19]. Fungal transformation was carried out as previously described [20] with the modification of embedding the protoplasts in 0.75% top agar rather than spreading them by a glass rod on solid media. Fungal chromosomal DNA was isolated and analyzed from lyophilized mycelia using previously described techniques [22].
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