Stress-induced cross-protection and combined stress responses in extremotolerant black yeasts

Fortuna, Klavdija (author), Kajin, Maja (author), Gostinčar, Cene (author)

Extremotolerant fungi inhabit environments with multiple overlapping stressors, yet most studies examine stresses individually. We tested whether preconditioning with salt, cold, or both improves survival after desiccation and freezing, and whether combined salinity and temperature effects on growth are additive or synergistic. We studied Aureobasidium pullulans, Aureobasidium subglaciale, Aureobasidium melanogenum, and Hortaea werneckii (haploid and diploid). All preconditioning treatments significantly increased long-term desiccation survival in A. pullulans, reflecting its generalist capacity to activate crossprotective responses. H. werneckii displayed smaller improvements, consistent with a specialist strategy. Freezing survival without cryoprotectants remained ~100% in both species, indicating high intrinsic tolerance. Growth analyses revealed synergistic effects of salinity and temperature in Aureobasidium spp. Species differed in salinity sensitivity (A. melanogenum > A. pullulans > A. subglaciale) and thermal preferences. A. melanogenum and A. pullulans grew faster at higher temperatures, while A. subglaciale showed the opposite trend. In H. werneckii, salinity governed growth. Haploids slowed as salinity increased, while the diploid remained unaffected. This is the first confirmation of the long-standing suggestion that hybrid diploid genomes of many H. werneckii are an adaptation to osmotic stress. These findings illustrate two pathways to extremotolerance: inducible flexibility in Aureobasidium versus constitutive halotolerance in H. werneckii.

• Language: English
• Keywords: Aureobasidium, Hortaea werneckii, ploidy, salt stress, temperature stress, combined stress effects, stress preconditioning, freezing survival, desiccation survival
• Typology: 1.01 - Original Scientific Article
• Organization: BF - Biotechnical Faculty
• Publication version: Version of Record
• Publication date: 01.01.2026
• Year: 2026
• Number of pages: Str. 1-22
• Numbering: Vol. 12, iss. 1
• PID: 20.500.12556/RUL-178068
• UDC: 577
• ISSN on article: 2309-608X
• DOI: 10.3390/jof12010043
• COBISS.SI-ID: 264995075
• Publication date in RUL: 26.01.2026

Record is a part of a journal

• Title: Journal of fungi
• Shortened title: J. Fungi
• Publisher: MDPI
• ISSN: 2309-608X
• COBISS.SI-ID: 525300761

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: Aureobasidium, Hortaea werneckii, ploidnost, solni stres, temperaturni stres, združeni učinki stresorjev, stresno predkondicioniranje, preživetje po zamrzovanju, preživetje po izsuševanju