Magnesium enhances the expression of arthroconidia-related genes in Trichosporon asahii

Trichosporon asahii is a pleomorphic basidiomycetous yeast that causes deep-seated mycoses in immunocompromised individuals. T. asahii exhibits three morphological types: hyphae, yeasts, and arthroconidia. Hyphal formation is related to virulence and is accelerated by the addition of magnesium. However, the effects of magnesium on gene expression have not been elucidated. In this study, we aimed to investigate whether gene expression is affected by magnesium. RNA sequencing and genetic analyses revealed that magnesium addition increased the expression of genes related to arthroconidia formation in T. asahii. We identified 11 magnesium-enhanced expression (mee) genes, whose expressions increased more than 5-fold. Deletion of mee4, mee5, mee6, and mee11 decreased arthroconidia formation. Furthermore, increased mee6 expression depended on mee4 and mee5, which lie downstream of the TOR pathway, and increased mee11 expression depended on mee4. In addition, mee11 inhibited the expression of other mee genes, and mee6 inhibited the expression of mee4. Overall, we identified a gene expression network related to arthroconidia formation in T. asahii, providing insights into the transition from hypha to arthroconidia and enhancing our understanding of fungal pathogenesis.

Magnesium induces cell elongation and changes in organelle distribution in T. asahii. In this study, RNA sequencing revealed that magnesium influenced gene expression. Among the genes whose expressions increased more than five-fold following magnesium addition, we identified arthroconidia-related genes whose deletions inhibited arthroconidia formation. Thus, an increase in magnesium cations promotes both hyphal formation and arthroconidia formation in T. asahii. This is the first study to elucidate genes related to arthroconidia formation.