Compatible solutes determine the heat resistance of conidia

Sjoerd J. Seekles, Tom van den Brule, Maarten Punt, Jan Dijksterhuis, Mark Arentshorst, Maryam Ijadpanahsaravi, Winfried Roseboom, Gwendolin Meuken, Véronique Ongenae, Jordy Zwerus, Robin A. Ohm, Gertjan Kramer, Han A.B. Wösten, Johannes H. de Winde, Arthur F.J. Ram*

*Corresponding author for this work

Research output: Contribution to journal/periodicalArticleScientificpeer-review

Abstract

Background: Asexually developed fungal spores (conidia) are key for the massive proliferation and dispersal of filamentous fungi. Germination of conidia and subsequent formation of a mycelium network give rise to many societal problems related to human and animal fungal diseases, post-harvest food spoilage, loss of harvest caused by plant-pathogenic fungi and moulding of buildings. Conidia are highly stress resistant compared to the vegetative mycelium and therefore even more difficult to tackle. Results: In this study, complementary approaches are used to show that accumulation of mannitol and trehalose as the main compatible solutes during spore maturation is a key factor for heat resistance of conidia. Compatible solute concentrations increase during conidia maturation, correlating with increased heat resistance of mature conidia. This maturation only occurs when conidia are attached to the conidiophore. Moreover, conidia of a mutant Aspergillus niger strain, constructed by deleting genes involved in mannitol and trehalose synthesis and consequently containing low concentrations of these compatible solutes, exhibit a sixteen orders of magnitude more sensitive heat shock phenotype compared to wild-type conidia. Cultivation at elevated temperature results in adaptation of conidia with increased heat resistance. Transcriptomic and proteomic analyses revealed two putative heat shock proteins to be upregulated under these conditions. However, conidia of knock-out strains lacking these putative heat shock proteins did not show a reduced heat resistance. Conclusions: Heat stress resistance of fungal conidia is mainly determined by the compatible solute composition established during conidia maturation. To prevent heat resistant fungal spore contaminants, food processing protocols should consider environmental conditions stimulating compatible solute accumulation and potentially use compatible solute biosynthesis as a novel food preservation target.

Original languageEnglish
Article number21
JournalFungal Biology and Biotechnology
Volume10
Issue number1
DOIs
Publication statusPublished - Dec 2023

Keywords

  • Aspergillus niger
  • Compatible solutes
  • Food preservation
  • Fungal spores
  • Heat shock proteins
  • Heat stress
  • Mannitol
  • Proteomics
  • Transcriptomics
  • Trehalose

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