Regular ArticlesTranscriptomic analysis of basidiocarp development in Ustilago maydis (DC) Cda.

- U. maydis basidiocarp formation involves differential regulation of 30% of its genome.
- The MAPK signal transduction pathway regulated basidiocarp development.
- Hydrophobins, laccases, ferric, and copper ions were very important for the process.
- TEC1, PRO1, FOXO3, MIG3 and SWI5 transcription factors controlled the whole process.
- We suggest that these genes were silenced after adaptation to a pathogenic lifestyle.

Previously, we demonstrated that when Ustilago maydis (DC) Cda., a phytopathogenic basidiomycete and the causal agent of corn smut, is grown in the vicinity of maize embryogenic calli in a medium supplemented with the herbicide Dicamba, it developed gastroid-like basidiocarps. To elucidate the molecular mechanisms involved in the basidiocarp development by the fungus, we proceeded to analyze the transcriptome of the process, identifying a total of 2002 and 1064 differentially expressed genes at two developmental stages, young and mature basidiocarps, respectively. Function of these genes was analyzed with the use of different databases. MIPS analysis revealed that in the stage of young basidiocarp, among the ca. two thousand differentially expressed genes, there were some previously described for basidiocarp development in other fungal species. Additional elements that operated at this stage included, among others, genes encoding the transcription factors FOXO3, MIG3, PRO1, TEC1, copper and MFS transporters, and cytochromes P450. During mature basidiocarp development, important up-regulated genes included those encoding hydrophobins, laccases, and ferric reductase (FRE/NOX). The demonstration that a mapkk mutant was unable to form basidiocarps, indicated the importance of the MAPK signaling pathway in this developmental process.

Schematic diagram that hypothesizes the mechanism of fruiting body development in U. maydis.123