The use of global transcriptional analysis to reveal the biological and cellular events involved in distinct development phases of Trichophyton rubrum conidial germination

Abstract

Background: Conidia are considered to be the primary cause of infections by Trichophyton rubrum.

Results: We have developed a cDNA microarray containing 10250 ESTs to monitor the transcriptional strategy of conidial germination. A total of 1561 genes that had their expression levels specially altered in the process were obtained and hierarchically clustered with respect to their expression profiles. By functional analysis, we provided a global view of an important biological system related to conidial germination, including characterization of the pattern of gene expression at sequential developmental phases, and changes of gene expression profiles corresponding to morphological transitions. We matched the EST sequences to GO terms in the Saccharomyces Genome Database (SGD). A number of homologues of Saccharomyces cerevisiae genes related to signalling pathways and some important cellular processes were found to be involved in T. rubrum germination. These genes and signalling pathways may play roles in distinct steps, such as activating conidial germination, maintenance of isotropic growth, establishment of cell polarity and morphological transitions.

Conclusion: Our results may provide insights into molecular mechanisms of conidial germination at the cell level, and may enhance our understanding of regulation of gene expression related to the morphological construction of T. rubrum.

Figure 1

Morphological transitions during conidial germination of T. rubrum. Dormant conidia were introduced into Sabouraud liquid medium and incubated at 28°C. 0 hr is dormant conidia. The 0 hr to 15 hr images were taken at the indicated time-points, and show the morphological transitions with time.

Figure 2

Hierarchical clustering of microarray data and identification of genes with similar transcriptional profiles. (A) Total of 1561 genes was clustered on the basis of their expression profiles across the sixteen time-points using TIGR MultiExperiment Viewer (MeV) software[17]. Each gene's expression values were standardized to have a median of zero and a standard deviation of one across the sixteen time points. The lighter colour in the cluster dendrogram is correlated with a higher expression level. Five distinct clusters were selected visually, and the node separating each cluster is shown in the distance tree. (B) An average expression profile of genes within each cluster. To obtain each profile, a sum of expression values across the sixteen time-points for each gene was standardized to 1. Next, time-course values for all genes in each cluster were summed, and the summed value for the sixteen time-points for each cluster was scaled to 1. (C) A sub-cluster of cluster I. (D) The name of each cluster and representative profile is shown in deferent colour.