Timecourse CAGE analysis of Madurella mycetomatis grain development in Galleria mellonella

Mycetoma is a neglected, chronic granulomatous infection of the subcutaneous tissue, most often caused by the fungal pathogen Madurella mycetomatis. Characteristic of the infection is the formation of grains. However, knowledge of the function and formation of the grain is limited. To map the processes leading to M. mycetomatis grain formation, we used a Galleria mellonella larvae infection model and time-course transcriptomic profiling. In the infected G. mellonella 88.0% of the RNA sequence reads mapped to G. mellonella, only 0.01% mapped to M. mycetomatis. Differential Gene Expression analysis revealed that 3.498 G. mellonella and 137 M. mycetomatis genes were differentially expressed during infection. Most of the enriched GO terms of both host and pathogen are linked to energy pathways, nucleobase metabolic process, and cation and iron transport. Genes related to iron transport were highly expressed by both G. mellonella (transferrin and ferritin) and M. mycetomatis (SidA, SidD and SidI). A protein-protein interaction network analysis of D. melanogaster homologues genes in M. mycetomatis revealed the expression of the entire siderophore biosynthesis pathway throughout infection. Many host and pathogen genes were differentially expressed during infection. The identification of the importance of iron acquisition during grain formation can be exploited as a potential novel diagnostic and therapeutic strategy for mycetoma. Galleria mellonella larvae were infected with M. mycetomatis genome strain Madurella mycetomatis. At 4h, 24h, 72h and 168h post-inoculation, RNA was extracted from larval content. LQ_ssCAGE libraries were prepared for time-course transcriptomic profiling and analysis.