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Updated: Jul 8, 2025
Isolation and Selection of Entomopathogenic Fungi from Soil Samples and Evaluation of Fungal Virulence against Insect Pests
Published on: September 28, 2021
Congo red induces trans-priming to UV-B radiation in Metarhizium robertsii
Karla Cecilia Licona-Juárez1, Ana Victória S Bezerra2, Ilkilene T C Oliveira2
1Universidade Brasil, São Paulo, SP, 08230-030, Brazil; Laboratorio de Biología Molecular, Tecnológico Nacional de Mexico, A. García Cubas 600, Celaya, Guanajuato, 38010, Mexico.
Abstract:
Metarhizium spp. is used as a biocontrol agent but is limited because of low tolerance to abiotic stress. Metarhizium robertsii is an excellent study model of fungal pathogenesis in insects, and its tolerance to different stress conditions has been extensively investigated. Priming is the time-limited pre-exposure of an organism to specific stress conditions that increases adaptive response to subsequent exposures. Congo red is a water-soluble azo dye extensively used in stress assays in fungi. It induces morphological changes and weakens the cell wall at sublethal concentrations. Therefore, this chemical agent has been proposed as a stressor to induce priming against other stress conditions in entomopathogenic fungi. This study aimed to evaluate the capacity of Congo red to induce priming in M. robertsii. Conidia were grown on potato dextrose agar with or without Congo red.The tolerance of conidia produced from mycelia grown in these three conditions was evaluated against stress conditions, including osmotic, oxidative, heat, and UV-B radiation. Conidia produced on medium supplemented with Congo red were significantly more tolerant to UV-B radiation but not to the other stress conditions assayed. Our results suggest that Congo red confers trans-priming to UV-B radiation but not for heat, oxidative, or osmotic stress.
Insights
Congo red priming enhanced Metarhizium robertsii's tolerance to UV-B radiation but not other stresses. This finding is crucial for improving biocontrol agents against environmental challenges.
Area of Science:
- Mycology
- Biocontrol
- Stress Physiology
Background:
- Metarhizium spp. are valuable biocontrol agents, but their efficacy is limited by poor tolerance to abiotic stress.
- Priming, a pre-exposure strategy, can enhance stress adaptation in organisms.
- Congo red, a dye used in fungal stress assays, can induce cellular changes.
Purpose of the Study:
- To investigate the potential of Congo red to induce priming in Metarhizium robertsii.
- To assess if Congo red pre-treatment enhances M. robertsii conidial tolerance to various abiotic stresses.
Main Methods:
- Metarhizium robertsii conidia were cultivated on potato dextrose agar with or without Congo red.
- The tolerance of resulting conidia was tested against osmotic, oxidative, heat, and UV-B radiation stress.
Main Results:
- Conidia produced on media containing Congo red exhibited significantly increased tolerance to UV-B radiation.
- No significant enhancement in tolerance was observed for osmotic, oxidative, or heat stress.
Conclusions:
- Congo red can induce a priming effect, specifically conferring trans-priming to UV-B radiation in Metarhizium robertsii.
- Congo red does not appear to induce priming against heat, oxidative, or osmotic stress in this fungus.
