Transcriptome analysis of itraconazole-tolerant versus susceptible Trichophyton indotineae

Trichophyton indotineae is a fungal species that was newly designated in 2020, when the organism was shown to be independent of the T. interdigitale / T. mentagrophytes complex. This species is highly infectious, and includes strains that are resistant to antifungal drugs. Here, we performed transcriptome analysis to elucidate the resistance mechanism of azole-resistant T. indotineae . A total of 6,887 expressed genes were detected in three sample RNAs, and the expression levels were compared between itraconazole (ITCZ)-treated (azole-resistant NUBS19006 ^T strain and azole-susceptible NUBS19007 strain) and ITCZ-free (NUBS19007) samples. The expression of 18 genes increased following treatment with ITCZ, with the TCONS_00001623 gene being the most highly expressed and, thus, presumed to be involved in azole resistance. Comparative nucleotide sequence analysis showed that the gene sequences were 93.5% identical to Trichophyton rubrum CBS 118892 uncharacterized protein (GenBank Accession No. XM_047748408.1), and 88.54% identical to a Nannizzia gypsea rhomboid family membrane protein (GenBank Accession No. XM_003170509.1). Therefore, the TCONS_00001623 gene might be a rhomboid family membrane protein gene. To confirm whether this gene is related to azole resistance, we constructed a T. indotineae strain by knocking out this gene, and performed antifungal susceptibility testing. Two TCONS_00001623-disrupted strains (∆TCONS_00001623-3 and ∆TCONS_00001623-4) were successfully established, and restoration of their susceptibility to azoles was confirmed. Therefore, this gene was presumed to be associated with azole resistance; however, its function remains unclear, necessitating further analysis.