Spatial differentiation of gene expression in Aspergillus niger colonies grown for sugar beet pulp utilization

Filamentous fungi are ubiquitous organisms and major plant biomass degraders. As a single colony, some fungal species can colonize large areas as up to five soccer stadia. During growth, the mycelium encounters heterogeneous carbon sources. Here we assessed whether substrate heterogeneity is a main determinant of spatial gene expression in colonies of Aspergillus niger. This question was addressed by analyzing whole-genome gene expression in five concentric zones of 5-day-old sugar beet pulp grown colonies. Growth, protein production and secretion were occurring throughout the whole colony. Carbon and nitrate utilization were constant from the centre to the periphery whereas genes encoding plant cell wall degrading enzymes were expressed with a different pattern across the colony. Finally our results demonstrate a fine-tuning of the different enzymatic tools available in A. niger and expand the knowledge on how this fungus adapts as it colonizes complex environments. We aim to discover differentially expressed genes accross in A.niger wild type strain N402 colony (five zones) while growing on sugar beet pulp as carbon source. Biological duplicates were made for RNA extraction. The RNAs were pooled for transcriptome studies. The strains were grown O/N in complete medium with 2% frunctose and mycelium was then washed and transferred to minimal medium with 25 mM D-galactose and incubated for 2 hours. Affymetrix microarray experiments were performed RNA isolated from these samples.