Identification and Characterization of Genetic Loci Associated With Environmental Thermotolerance in Native Strains of Aspergillus salvadorensis (2025)

Thermotolerance in Aspergillus salvadorensis is based on an integrated network of molecular and physiological responses activated to heat stress. Genomic analysis showed open reading frames corresponding to atg1, atg7 and atg8 in genes of the ATG system (Autophagy-related genes). These participate in the detection of heat-induced protein damage, autophagosome biogenesis and the recycling of altered macromolecules, contributing to the maintenance of cellular homeostasis. The induction of heat shock proteins, particularly Hsp20 and Hsp70, whose overexpression under high temperatures confirms their function as molecular chaperones, was also identified. These stabilize partially denatured proteins, prevent their aggregation and facilitate their functional folding. The presence of HSE-like regulatory sequences (Heat Shock Elements) in promoter regions supports specific transcriptional activation dependent on thermal stimulus. The energy component is also decisive. The detection of ATP synthase subunits, NADPH-dependent enzymes and elements associated with the AMPK-like pathway (AMP-Activated Protein Kinase) indicates an increase in energy demand and metabolic monitoring systems. Sustained ATP production is essential to sustain repair processes, intracellular transport and protein quality control. Without ATP, fungal cells would not be able to respond to extreme temperatures. Heat stress increases the generation of reactive oxygen species, which induces the activation of antioxidant systems such as superoxide dismutase, catalases and peroxidases, together with NADPH (Nicotinamide Adenine Dinucleotide Phosphate) regeneration mechanisms, configuring a protective redox response. Experimentally, mycelial growth decreases progressively and around 50 °C metacaspases associated with regulated cell death are activated, establishing the physiological limit of thermal tolerance. In conclusion, heat resistance in A. salvadorensis depends on the coordinated interaction between autophagy, chaperones, energy regulation, antioxidant defense and structural remodeling, mechanisms that guarantee its viability in high temperature environments in summer when El Salvador has a tropical savannah climate.