Biological Characterization, Domestication, and the Molecular Basis of Iron Enrichment in a Wild Flammulina yunnanensis Strain.

In this paper, we reported a wild strain Z68, isolated from Tibet, was identified as Flammulina yunnanensis based on ITS sequence and phylogenetic analysis. Optimal condition for its mycelial growth (maltose, yeast extract, magnesium sulfate, 20 °C and pH 7.0-8.0) and fruiting ability was confirmed. Its fruiting bodies contained 25.1 g/100 g protein and 19.80 g/100 g of 16 amino acids, with iron, potassium and zinc, contents significantly higher than these in the controls F. fennae and F. velutipes. Significantly, whole-genome sequencing and comparative analysis of iron-metabolism gene families were performed between F. yunnanensis, F. fennae and F. velutipes to elucidate the basis of its notably elevated iron content, revealing most single copied and conserved iron-related gene families and two-fold expanded iron permease FTR1 in F. yunnanensi, which is the iron-sulfur cluster assembly protein family. Sequence, topology (DeepTMHMM), and structural-confidence (ColabFold/AlphaFold2) analyses of FTR1 identified six species-specified physicochemical substitutions, of which a charge reverse at the intracellular channel (Glu→Lys) and a polar-to-nonpolar change in the TM3 pore (Ser→Ala) were predicted to enhance iron transport efficiency. These suggested a possible two-tier mechanism underlying the elevated iron content of F. yunnanensis, combining gene-family expansion and predicted functional fine-tuning of the FTR1 permease. This study provided insight for biological characterization, domestication, and the molecular basis of iron enrichment in a F. yunnanensis Z68.