The HOG signal pathway contributes to survival strategies of the piezo-tolerant fungus Aspergillus sydowii DM1 in hadal sediments.

Abstract

The hadal zone, one of Earth's most extreme ecosystems, harbors diverse and unique microbial communities adapted to its harsh environmental conditions, including high hydrostatic pressure (HHP) and low temperatures. Within these communities, deep-sea fungi play a critical role in geochemical cycling and marine ecosystem functioning; however, research on their cultivable strains and adaptation mechanism remains scarce. In this study, the piezo-tolerant fungus Aspergillus sydowii DM1, isolated from the Mariana Trench sediments (10,898 m), was selected as a representative strain. A comprehensive genome analysis using high-throughput sequencing revealed a genome size of 34.5 Mb, with 12,241 predicted genes. Functional annotations across multiple databases identified a substantial number of pathways associated with environmental adaptations, including extensive carbohydrate, amino acid, sulfur, and nitrogen metabolic pathways. Among them, the HOG (high-osmolarity glycerol) signal pathway, which responds to external stimuli, was indicated to play a crucial role. To study the HOG signal pathways in more detail, we developed a knockout technique for A. sydowii and constructed a hog1 mutant strain (ΔAshog1). The ΔAshog1 strain displayed notable differences in colony phenotype, spore production, secondary metabolites, and oxidative stress tolerance compared to the wild type. Furthermore, the Ashog1 gene was found to regulate reactive oxygen species (ROS) and ATP levels in response to osmotic pressure and HHP, suggesting a role of hog1 in the fungal adaptation to this extreme environment. Our study serves as an ideal candidate for exploring gene functions in extreme microorganisms and carries significant implications for understanding the adaptive mechanisms of hadal microorganisms.

Importance: Research on the genomes and gene functions of hadal zone fungi is crucial for understanding life's adaptation to extreme environments. However, current studies on constructing genetic operation systems for marine-derived filamentous fungi are scarce, and research on HHP environments in related fields is virtually non-existent. Our study highlights the critical role of the HOG-mediated pathway in regulating stress responses and metabolic processes in extremophiles, a regulatory mechanism that had not been previously investigated under HHP conditions. Notably, the whole-genome annotation of the hadal fungus Aspergillus sydowii DM1 advances our understanding of the life processes of hadal fungi. The development of gene knockout technology, combined with insights into stress adaptation and metabolic regulation in A. sydowii strain DM1, provides a strong foundation for future research and biotechnological applications.