• Reveals the physiological salt tolerance strategy of Auricularia heimuer across both mycelial and fruiting body stages through integrated biochemical and transcriptomic analyses. • Identifies 1,342 salt-responsive genes, with significant enrichment in cell cycle regulation, spore wall formation, and amino sugar/nucleotide sugar metabolic pathways. • Demonstrates that key mannose biosynthesis genes PMI (g2692) and GMPP (g2546) are significantly upregulated under salt stress. • Shows that enhanced mannose accumulation strengthens cell wall stability and osmotic regulation, contributing to improved salt tolerance. • Provides new genetic targets and theoretical support for breeding salt-tolerant edible fungi cultivars. Salt stress severely limits the cultivation and productivity of Auricularia heimuer . In this study, physiological and transcriptomic analyses were integrated to elucidate the salt tolerance mechanisms of A. heimuer using a salt-tolerant strain (H2) and a salt-sensitive strain (H26). At the mycelial stage, increasing NaHCO₃ concentrations significantly inhibited growth and induced oxidative stress in both strains; however, H2 exhibited higher growth rates, lower pigment secretion, reduced membrane lipid peroxidation, and significantly enhanced antioxidant enzyme activities compared with H26. Under moderate salt stress, H2 accumulated higher levels of soluble proteins, total sugars, and trehalose, indicating superior osmotic adjustment capacity. At the fruiting body stage, salt stress altered morphology and physiological traits of H2, with moderate NaHCO₃ levels promoting osmolyte accumulation and antioxidant defense, while excessive stress caused oxidative damage and growth inhibition. Transcriptome sequencing of H2 fruiting bodies under high salt stress identified 1,342 differentially expressed genes, with significant enrichment in carbohydrate metabolism, nucleotide sugar metabolism, and protein processing in the endoplasmic reticulum. Further analysis revealed that the genes g2692 and g2546 , encoding the key enzymes involved in GDP-mannose biosynthesis-mannose-6-phosphate isomerase (PMI) and GDP-mannose pyrophosphorylase (GMPP), respectively-were significantly upregulated. Quantitative expression analysis confirmed higher expression of these genes in H2 than in H26 under salt stress, accompanied by a marked increase in intracellular mannose content. These results demonstrate that enhanced osmotic regulation, antioxidant capacity, and activation of the GDP-mannose biosynthesis pathway collectively contribute to salt tolerance in A. heimuer , providing a physiological and molecular basis for improving saline-alkaline adaptability in edible fungi cultivation.
Sun et al. (Tue,) studied this question.