title: Metabolic activity in dormant conidia of Aspergillus niger and developmental changes during conidial outgrowth.
abstract: The early stages of development of Aspergillus niger conidia during outgrowth were explored by combining genome-wide gene expression analysis (RNAseq), proteomics, Warburg manometry and uptake studies. Resting conidia suspended in water were demonstrated for the first time to be metabolically active as low levels of oxygen uptake and the generation of carbon dioxide were detected, suggesting that low-level respiratory metabolism occurs in conidia for maintenance. Upon triggering of spore germination, generation of CO2 increased dramatically. For a short period, which coincided with mobilisation of the intracellular polyol, trehalose, there was no increase in uptake of O2 indicating that trehalose was metabolised by fermentation. Data from genome-wide mRNA profiling showed the presence of transcripts associated with fermentative and respiratory metabolism in resting conidia. Following triggering of conidial outgrowth, there was a clear switch to respiration after 25min, confirmed by cyanide inhibition. No effect of SHAM, salicylhydroxamic acid, on respiration suggests electron flow via cytochrome c oxidase. Glucose entry into spores was not detectable before 1h after triggering germination. The impact of sorbic acid on germination was examined and we showed that it inhibits glucose uptake. O2 uptake was also inhibited, delaying the onset of respiration and extending the period of fermentation. In conclusion, we show that conidia suspended in water are not completely dormant and that conidial outgrowth involves fermentative metabolism that precedes respiration.
authors.affiliation: School of Life Sciences, University of Nottingham, Nottingham NG7 2RD, UK. Electronic address: michaela.novodvorska@hotmail.com.
authors.forename: Michaela
authors.initials: M
authors.lastname: Novodvorska
authors.affiliation: School of Life Sciences, University of Nottingham, Nottingham NG7 2RD, UK; Mologic Ltd, Bedford Technology Park, Thurleigh, Bedfordshire MK44 2YA, UK. Electronic address: malcolm.stratford@mologic.co.uk.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Stratford
authors.affiliation: Deep Seq, Faculty of Medicine and Health Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2RD, UK. Electronic address: martinblythe@hotmail.com.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Blythe
authors.affiliation: Deep Seq, Faculty of Medicine and Health Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2RD, UK. Electronic address: raywilsonphotography@googlemail.com.
authors.forename: Raymond
authors.initials: R
authors.lastname: Wilson
authors.affiliation: Biological Mass Spectrometry Facility biOMICS, University of Sheffield, Brook Hill Road, Sheffield S3 7HF, UK. Electronic address: rbeniston@hotmail.com.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Beniston
authors.affiliation: School of Life Sciences, University of Nottingham, Nottingham NG7 2RD, UK. Electronic address: david.archer@nottingham.ac.uk.
authors.forename: David B
authors.initials: DB
authors.lastname: Archer
mesh_terms: D001234:Aspergillus niger / Q000254:growth & development / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D012331:RNA, Fungal / Q000378:metabolism; D013011:Sorbic Acid / Q000378:metabolism; D013172:Spores, Fungal / Q000254:growth & development / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D012331:RNA, Fungal; D010100:Oxygen; D013011:Sorbic Acid
keywords: Aspergillus niger; Conidial development; Manometry; Proteome; RNAseq; Sorbic acid