Cutaneous mycoses are common human infections among healthy and immunocompromised hosts, and the anthropophilic fungus Trichophyton rubrum is the most prevalent microorganism isolated from such clinical cases worldwide. The aim of this study was to determine the transcriptional profile of T. rubrum exposed to various stimuli in order to obtain insights into the responses of this pathogen to different environmental challenges. Therefore, we generated an expressed sequence tag (EST) collection by constructing one cDNA library and nine suppression subtractive hybridization libraries.
The 1388 unigenes identified in this study were functionally classified based on the Munich Information Center for Protein Sequences (MIPS) categories. The identified proteins were involved in transcriptional regulation, cellular defense and stress, protein degradation, signaling, transport, and secretion, among other functions. Analysis of these unigenes revealed 575 T. rubrum sequences that had not been previously deposited in public databases.
In this study, we identified novel T. rubrum genes that will be useful for ORF prediction in genome sequencing and facilitating functional genome analysis. Annotation of these expressed genes revealed metabolic adaptations of T. rubrum to carbon sources, ambient pH shifts, and various antifungal drugs used in medical practice. Furthermore, challenging T. rubrum with cytotoxic drugs and ambient pH shifts extended our understanding of the molecular events possibly involved in the infectious process and resistance to antifungal drugs.
Trichophyton rubrum is a cosmopolitan dermatophyte that colonizes human skin and nails and is the most prevalent cause of human dermatophytoses [1,2]. During the initial stages of the infection, dermatophytes induce the expression of adhesins and unspecific proteases and keratinases that have optimum activity at acidic pH values , which is probably because the human skin has an acidic pH value . The secretion of these proteases, which have been identified as an important step in fungal pathogenicity and virulence [5,6], act on keratinous and nonkeratinous substrates to release peptides that are further hydrolyzed to amino acids by putative peptidases. The metabolism of some amino acids shifts the extracellular pH from acidic to alkaline values at which most known keratinolytic proteases have optimal enzymatic activity[7–9]. T. rubrum also responds to the environmental pH by altering its gene expression profile[9,10].
Molecular studies have been performed with human pathogens such as Candida albicans,Histoplasma capsulatum, and Paracoccidioides brasiliensis, and the results thus obtained have helped to determine the fungal transcriptional profile and characterize the genes involved in host-pathogen interactions and environmental stress responses [11–13]. Previously, a collection of T. rubrum expressed sequence tags (ESTs) was obtained from distinct developmental phases[14,15]. However, determining the transcriptional profiles in response to different cell stimuli is necessary for extending our understanding of diverse cellular events, and the results from such studies may reveal new signal transduction networks and the activation of specific metabolic pathways. Functional analysis of the genes involved in these molecular events will help in evaluating their roles as putative cellular targets in the development of new antifungal agents.
Our study aimed to extend the T. rubrum genomic database by adding expressed gene resources that cover different aspects of cellular metabolism. Moreover, the data can help to generate useful information to screen valuable genes for functional and postgenomic analyses. The EST collection described here revealed the metabolic adaptations of the human pathogen T. rubrum to changes in the ambient pH and carbon sources and also provided information on the adaptive responses to several cytotoxic drugs.
Transcriptional profiling reveals the expression of novel genes in response to various stimuli in the human dermatophyte Trichophyton rubrum
Nalu TA Peres1, Pablo R Sanches1, Juliana P Falcão1,3, Henrique CS Silveira1, Fernanda G Paião1, Fernanda CA Maranhão1, Diana E Gras1, Fernando Segato1, Rodrigo A Cazzaniga1,Mendelson Mazucato1, Jeny R Cursino-Santos1, Roseli Aquino-Ferreira1, Antonio Rossi2and Nilce M Martinez-Rossi1*
*Corresponding author: Nilce M Martinez-Rossi firstname.lastname@example.org
1Departamento de Genética, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14049-900, SP, Brazil
2Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto 14049-900, SP, Brazil
3Current address: Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, 14040-903, Ribeirão Preto, SP, Brazil
BMC Microbiology 2010, 10:39 doi:10.1186/1471-2180-10-39
The electronic version of this article is the complete one and can be found online at:http://www.biomedcentral.com/1471-2180/10/39