Transcriptomic analysis of the role of Rim101/PacC in the adaptation of Ustilago maydis to an alkaline environment.

Alkaline pH triggers an adaptation mechanism in fungi that is mediated by Rim101/PacCp, a zinc finger transcription factor. To identify the genes under its control in Ustilago maydis, we performed microarray analyses, comparing gene expression in a wild-type strain versus a rim101/pacC mutation strain of the fungus. In this study we obtained evidence of the large number of genes regulated mostly directly, but also indirectly (probably through regulation of other transcription factors), by Rim101/PacCp, including proteins involved in a large number of physiological activities of the fungus. Our analyses suggest that the response to alkaline conditions under the control of the Pal/Rim pathway involves changes in the cell wall and plasma membrane through alterations in their lipid, protein and polysaccharide composition, changes in cell polarity, actin cytoskeleton organization, and budding patterns. Also as expected, adaptation involves regulation by Rim101/PacC of genes involved in meiotic functions, such as recombination and segregation, and expression of genes involved in ion and nutrient transport, as well as general vacuole functions.