02657nas a2200277   4500008004100000245007600041210006900117300001200186490000600198520157700204653011001781653008001891653001701971653001801988653005402006653006902060100001802129700002102147700001502168700001802183700001402201700001802215700002102233700001902254856010602273       2007                        eng d00aSpatial differentiation in the vegetative mycelium of Aspergillus niger0 aSpatial differentiation in the vegetative mycelium of Aspergillu  a2311-220 v63 aFungal mycelia are exposed to heterogenic substrates. The substrate in the central part of the colony has been (partly) degraded, whereas it is still unexplored at the periphery of the mycelium. We here 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 7-day-old maltose- and xylose-grown colonies. Expression profiles at the periphery and the center were clearly different. More than 25% of the active genes showed twofold differences in expression between the inner and outermost zones of the colony. Moreover, 9% of the genes were expressed in only one of the five concentric zones, showing that a considerable part of the genome is active in a restricted part of the colony only. Statistical analysis of expression profiles of colonies that had either been or not been transferred to fresh xylose-containing medium showed that differential expression in a colony is due to the heterogeneity of the medium (e.g., genes involved in secretion, genes encoding proteases, and genes involved in xylose metabolism) as well as to medium-independent mechanisms (e.g., genes involved in nitrate metabolism and genes involved in cell wall synthesis and modification). Thus, we conclude that the mycelia of 7-day-old colonies of A. niger are highly differentiated. This conclusion is also indicated by the fact that distinct zones of the colony grow and secrete proteins, even after transfer to fresh medium.10aAspergillus niger/*metabolism Cell Wall/metabolism Fungal Proteins/metabolism *Gene Expression Regulation10aBiological Mycelium/*metabolism Oligonucleotide Array Sequence Analysis RNA10aFungal Genes10aFungal Genome10aFungal Glucans/chemistry Maltose/chemistry Models10aFungal Time Factors Trans-Activators/metabolism Xylose/chemistry1 aLevin, A., M.1 ade Vries, R., P.1 aConesa, A.1 ade Bekker, C.1 aTalon, M.1 aMenke, H., H.1 avan Peij, N., N.1 aWosten, H., A.  uhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=17951513