Phs1 and the Synthesis of Very Long Chain Fatty Acids Are Required for Ballistospore Formation

Abstract

The production and dissemination of spores by members of the fungal kingdom is a major reason for the success of this eukaryotic lineage in colonizing most terrestrial ecosystems. Ballistospores are a type of spore produced by basidiomycete fungi, such as the mushrooms and plant pathogenic rusts. These spores are forcefully discharged through a unique liquid-drop fusion mechanism, enabling the aerosolization of these particles that can contribute to plant disease and human allergies. The genes responsible for this process are unknown due to technical challenges in studying many of the fungi that produce ballistospores. Here, we applied newly-developed techniques in a forward genetic screen to identify genes required for ballistospore formation or function in a tractable red yeast, a species of Sporobolomyces. One strain bearing a mutation in the PHS1 gene was identified as a mirror mutant. PHS1 encodes 3-hydroxyacyl-CoA dehydratase required for the third step in very long chain fatty acid biosynthesis. The Sporobolomyces PHS1 gene complements the essential functions of a S. cerevisiae phs1 mutant. The Sporobolomyces phs1 mutant strain has less dehydratase activity and a reduction in very long chain fatty acids compared to wild type. The mutant strain also exhibits sensitivity to cell wall stress agents and loss of shooting due to a delay in ballistospore formation, indicating that the role of Phs1 in spore dissemination may be primarily in cellular integrity.

Whole genome sequencing and comparative genomic analysis of oleaginous red yeast Sporobolomyces pararoseus NGR identifies candidate genes for biotechnological potential and ballistospores-shooting

“…Recently, Ianiri et al reported that 3-hydroxyacyl-CoA dehydratase gene Phs1 is not only responsible for the very long chain fatty acid biosynthesis, but also for the ballistospores-shooting in Sporobolomyces sp. IAM 13481 [31]. However, we found this Phs1 gene in the both S. pararoseus NGR and R. toruloides genomes.…”

Transcriptomic responses of the basidiomycete yeast Sporobolomyces sp. to the mycotoxin patulin

“…Strand-specific libraries were prepared from RNA isolated from Sporobolomyces sp. 1) yeast cells grown in the presence and in the absence of 5 μg/ml of PAT (two biological replicates for each of two samples), 2) yeast cells collected from YPD agar medium after 2 days of incubation, 3) ballistospore cells fired on a YPD agar mirror plate, a spore dispersal system that we previously described [ 37 ]. The table in Additional file 1 summarizes the samples used for RNA extraction, the type of libraries generated and their use for downstream analysis (i.e.…”

“…Besides the incubation in the presence of PAT, Sporobolomyces sp. RNA was extracted also from cells collected on YPD agar after two days of growth, and from fired ballistospores collected from a mirror YPD plate [ 37 ]; in the present study these data were only used for the generation of the Sporobolomyces sp. reference transcriptome (Additional file 1 ).…”

A silver bullet in a golden age of functional genomics: the impact of Agrobacterium-mediated transformation of fungi

“…IAM 13481 were used to investigate the molecular basis of the intriguing mechanism of ballistospore formation and dispersal that is unique to basidiomycete fungi. This property can be evaluated in the laboratory by the production of a mirror image of a culture from one Petri dish onto an uninoculated second dish [ 193 ]. The screen of more than 5000 transformants led to identification of 18 mirror mutants unable to shoot spores to produce the mirror image.…”

“…Strikingly, PHS1 is an essential gene in other fungi, and its identification in a Sporobolomyces sp. mutant was fortuitous as the T-DNA inserted within the last intron of the gene and past the essential amino acid residues required for function, which resulted in the production of an altered transcript yet still viable phenotype [ 193 ].…”