Abstract
Ashbya gossypii is a filamentous ascomycete belonging to the yeast family of Saccharomycetaceae. At the end of its growth phase Ashbya generates abundant amounts of riboflavin and spores that form within sporangia derived from fragmented cellular compartments of hyphae. The length of spores differs within species of the genus. Needle-shaped Ashbya spores aggregate via terminal filaments. A. gossypii is a homothallic fungus which may possess a and α mating types. However, the solo-MATa type strain is self-fertile and sporulates abundantly apparently without the need of prior mating. The central components required for the regulation of sporulation, encoded by IME1, IME2, IME4, KAR4, are conserved with Saccharomyces cerevisiae. Nutrient depletion generates a strong positive signal for sporulation via the cAMP-PKA pathway and SOK2, which is also essential for sporulation. Strong inhibitors of sporulation besides mutations in the central regulatory genes are the addition of exogenous cAMP or the overexpression of the mating type gene MATα2. Sporulation has been dissected using gene-function analyses and global RNA-seq transcriptomics. This revealed a role of Msn2/4, another potential PKA-target, for spore wall formation and a key dual role of the protein A kinase Tpk2 at the onset of sporulation as well as for breaking the dormancy of spores to initiate germination. Recent work has provided an overview of ascus development, regulation of sporulation and spore maturation. This will be summarized in the current review with a focus on the central regulatory genes. Current research and open questions will also be discussed.
Highlights
As a plant pathogen A. gossypii causes a yeast spot disease termed stigmatomycosis e.g., on cotton, pistachio or soybean [1]
Nutrient depletion generates a strong positive signal for sporulation via the cAMP-PKA pathway and SOK2, which is essential for sporulation
Strong inhibitors of sporulation besides mutations in the central regulatory genes are the addition of exogenous cAMP or the overexpression of the mating type gene MATα2
Summary
As a plant pathogen A. gossypii causes a yeast spot disease termed stigmatomycosis e.g., on cotton, pistachio or soybean [1]. Comparative genomics studies within the genus of Eremothecium revealed chromosome number reductions from eight to seven chromosomes in Ashbya gossypii and A. aceri and from eight to six chromosomes in E. coryli. The poly-Q-protein Whi has a key role for the localization of mRNAs of key polarity factors Bni and Spa at sites of polarized growth [32]. This control of aggregates in a cytoplasmic space is dependent on differential phosphorylation of Whi3 [33]. We describe research elucidating the molecular genetics of sporulation in A. gossypii and summarize open questions of fundamental fungal biology requiring further research
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
