Submitted to: Eukaryotic Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2008
Publication Date: 9/1/2008
Citation: Kasuga, T., Glass, N.L. 2008. DISSECTING COLONY DEVELOPMENT OF NEUROSPORA CRASSA USING mRNA PROFILING AND COMPARTATIVE GENOMICS APPROACHES. Eukaryotic Cell. Vol. 7, No. 9, pp1549-1564. Interpretive Summary: A colony of fungus is comprised of long, branching filamentous cells called hyphae. Genetic mechanisms underlying the development of hyphae are poorly understood. We sectioned hyphae of a model fungus, Neurospora crassa (pink bread mold), into six parts depending on the age of the cells; 1 hour, 3 hour, 9 hour, 15 hour, 21 hour and 27 hour old, respectively, and analyzed functions of genes active in each of the sections. We found that genes involved in cell membrane biosynthesis, polar growth and cellular signaling were active in the 1 hour section. Genes involved in protein synthesis and energy production were active in the 9 and 15 hours old sections. In the older sections (21 and 27 hours old) genes involved in protein degradation were found to be active.
Technical Abstract: Colony development, which includes hyphal extension, branching, anastomosis and asexual sporulation are fundamental aspects of the lifecycle of filamentous fungi; genetic mechanisms underlying these phenomena are poorly understood. We conducted transcriptional profiling during colony development of the model filamentous fungus, Neurospora crassa, using 70-mer oligonucleotide microarrays. Relative mRNA expression levels were determined for six sections of defined age excised from a 27 hr old N. crassa colony. Functional category analysis showed that the expression of genes involved in cell membrane biosynthesis, polar growth and cellular signaling were enriched at the periphery of the colony. The relative expression level of genes involved in protein synthesis and energy production were enriched in the middle section of the colony, while sections of the colony undergoing asexual development (conidiogenesis) were enriched in expression level for genes involved in protein/peptide degradation and unclassified proteins. A cross-examination of the N. crassa dataset with a published dataset of Aspergillus niger revealed shared patterns in the spatiotemporal regulation of gene orthologs during colony development. At present less than 50% of genes in N. crassa have functional annotation, which imposes the chief limitation on data analysis. Using an evolutionary approach, we observed that the expression of phylogenetically conserved groups of genes was enriched in the middle section of a N. crassa colony, whereas expression of genes unique to euascomycete species as well as N. crassa-orphan genes was enriched at the colony periphery and in the older, conidiating sections of a fungal colony.