A. nidulans wild type strain transcriptome analysis upon 100 µM farnesol treatment.

Farnesol is a nonsterol isoprenoid produced by dephosphorylation of farnesyl pyrophosphate, a catabolite of the cholesterol biosynthetic pathway. These isoprenoids have been reported to inhibit proliferation and induce apoptosis in neoplastic cell lines as well as to be effective in chemotherapy in several in vivo cancer models. Recently, it was shown that farnesol triggers morphological features characteristic of apoptosis in the filamentous fungus Aspergillus nidulans. In order to investigate which pathways are involved under Farnesol treatment, we determined the transcriptional profile of A. nidulans wild type strain. Conidia were incubated at 37°C in complete medium for 16 hours and were esposed or not to 100 μM Farnesol for 2 hours. The mycelia were harvested by centrifugation and used for competitive microarray hybridizations. We detected differential regulation of genes involved in a variety of cellular processes whose specific modulation is likely to be implicated with A. nidulans adaptation to farnesol. We observed decreased mRNA abundance of several genes involved in RNA processing and modification, transcription, translation, ribosomal structure and biogenesis, amino acid transport and metabolism. Interestingly, several genes involved in the ergosterol biosynthesis (such as the homologues of erg4/24, 11A, -11B, -13, -25, and –28) have decreased mRNA accumulation and other genes encoding mitochondrial proteins [such as AN9103.3, AN4500.3, and AN5440.3, encoding the Apoptosis Inducing Factor (AIF)-like mitochondrial oxidoreductase, the mitochondrial ATPase inhibitor, and the cytochrome c peroxidase, respectively] have increased mRNA expression when A. nidulans was exposed to farnesol. We also observed as more expressed several genes encoding proteins involved in trehalose metabolism and chaperones. Keywords: farnesol effect For the microarray experiments, 1.0 x 1010 conidia/ml of A. nidulans wild type (GR5) were used to inoculate 400 ml of pre-warmed liquid cultures (YG) in 1000-ml erlenmeyer flasks that were incubated in a reciprocal shaker (250 rpm) at 37°C for 12 hours. After this period, the germlings were exposed or not (timepoint 0 min) to 100 µM FOH for 2 hours at 37oC. Germilings were harvested by centrifugation and total RNA was extracted. Hybridization experiments were competitive using probes derived from wild type strain exposed to farnesol for 2 hours using the timepoint zero (control) as the reference RNA for every hybridizantion. Normalized signal intensities were used to generate relative hybridization ratios (query/reference). Following normalization, the values for each gene's in-slide replicates were condensed (median variance <0.01), and the flip-dye replicates were averaged to compensate for dye-specific effects (see Supplementary file linked below).