Abstract
BackgroundGenome-wide analysis was performed to assess the transcriptional landscape of germinating A. niger conidia using both next generation RNA-sequencing and GeneChips. The metabolism of storage compounds during conidial germination was also examined and compared to the transcript levels from associated genes.ResultsThe transcriptome of dormant conidia was shown to be highly differentiated from that of germinating conidia and major changes in response to environmental shift occurred within the first hour of germination. The breaking of dormancy was associated with increased transcript levels of genes involved in the biosynthesis of proteins, RNA turnover and respiratory metabolism. Increased transcript levels of genes involved in metabolism of nitrate at the onset of germination implies its use as a source of nitrogen. The transcriptome of dormant conidia contained a significant component of antisense transcripts that changed during germination.ConclusionDormant conidia contained transcripts of genes involved in fermentation, gluconeogenesis and the glyoxylate cycle. The presence of such transcripts in dormant conidia may indicate the generation of energy from non-carbohydrate substrates during starvation-induced conidiation or for maintenance purposes during dormancy. The immediate onset of metabolism of internal storage compounds after the onset of germination, and the presence of transcripts of relevant genes, suggest that conidia are primed for the onset of germination. For some genes, antisense transcription is regulated in the transition from resting conidia to fully active germinants.
Highlights
Genome-wide analysis was performed to assess the transcriptional landscape of germinating A. niger conidia using both generation RNA-sequencing and GeneChips
RNA-sequencing technology (RNA-seq) was used for the first time to uncover transcriptome changes at the breaking of dormancy of A. niger conidia
Our data showed that the transcriptome of dormant conidia contains transcripts of genes whose respective proteins were active during conidiation and transcripts of genes necessary for immediate onset of germination
Summary
Genome-wide analysis was performed to assess the transcriptional landscape of germinating A. niger conidia using both generation RNA-sequencing and GeneChips. Decarboxylation of the food preservative, sorbic acid, is a transcription-dependent and time-dependent activity in developing conidia of A. niger [4] Fungal cells adapt their metabolism in response to environmental nutrient availability and transcripts and proteins present in dormant and germinating conidia reflect, to some extent, the culture conditions [5]. Aspergillus fumigatus conidia, for example, will not germinate in the absence of water, a degradable carbon source or oxygen [11] Compatible solutes such as mannitol and trehalose serve as storage carbon sources and give conidia the ability to survive in stress conditions, in elevated temperatures and drought [12,13]. Glycerol is the first polyol that disappears during starvation and its biosynthesis occurs during the germination of fungal conidia [13] especially in oxygen-rich environments [12]
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