Transcriptional Analysis

RNA extraction, purification and quality control, as well as cDNA synthesis were performed as previously detailed [20]. RNA integrity numbers of the purified samples were between 7.8 and 9.2. cDNA was synthesized using the primers listed in Supplementary Table 1. The gene gmk (coding for guanylate kinase) was selected from 9 candidates as the internal control gene, due to a nearly constant Cq value in all strains (Table S2). RT-qPCR was performed as described before [21], and the transcription levels calculated after Livak and Schmittgen [22]. These experiments were compliant with MIQE guidelines [23].