Transcriptional analysis of the adaptation of Ustilago maydis to grow under nitrogen fixation conditions

In this study we show the transcriptional analysis after shifting the Ustilago maydis from media with ammonium as a nitrogen source to media lacking ammonium. From these, 49 genes were up-regulated and 41 were down-regulated. The functional description and gene ontology terms associated to the diferentially expressed genes revealed that various key pathways were represented, including, secondary metabolism, the metabolism of nitrogen, amino acid, fatty acid and amino sugar, among others, suggesting that the interplay of U. maydis with its N2 fixing bacterial endosymbiont is a flexible process that may be active during the adaptation to the fungus to the different nitrogen sources, and possibly during its pathogenic style of life. Overall design: The strain of U. maydis used in this study was FB2. The strain, was maintained at -70 ºC, recovered in complete medium and then grown in liquid minimum medium (MM) at 28 ºC. U. maydis cells were inoculated to MM with (NH4)NO3 as nitrogen source (+N), and in the same basal medium without (NH4)NO3 (-N), and incubated under shaking conditions at 28 ºC for 24 h. To identify the differentially expressed genes of U. maydis cells growing fixation conditions, we prepared two RNA-Seq libraries from three biological replicates pooled of yeast-like cells of U. maydis FB2 strain grown with an added nitrogen source (+N), or without an added nitrogen source (-N) obtained at the end of the log phase (24h). The RNA-seq libraries were sequenced by Illumina HiSeq200 using the paired-end protocol (Illumina Inc. San Diego, CA, USA).