Chlamydospore development in the absence of protein synthesis in Fusarium solani

Protein profile and protein interaction network of Moniliophthora perniciosa basidiospores

BACKGROUND

Witches' broom, a disease caused by the basidiomycete Moniliophthora perniciosa, is considered to be the most important disease of the cocoa crop in Bahia, an area in the Brazilian Amazon, and also in the other countries where it is found. M. perniciosa germ tubes may penetrate into the host through intact or natural openings in the cuticle surface, in epidermis cell junctions, at the base of trichomes, or through the stomata. Despite its relevance to the fungal life cycle, basidiospore biology has not been extensively investigated. In this study, our goal was to optimize techniques for producing basidiospores for protein extraction, and to produce the first proteomics analysis map of ungerminated basidiospores. We then presented a protein interaction network by using Ustilago maydis as a model.

RESULTS

The average pileus area ranged from 17.35 to 211.24 mm(2). The minimum and maximum productivity were 23,200 and 6,666,667 basidiospores per basidiome, respectively. The protein yield in micrograms per million basidiospores were approximately 0.161; 2.307, and 3.582 for germination times of 0, 2, and 4 h after germination, respectively. A total of 178 proteins were identified through mass spectrometry. These proteins were classified according to their molecular function and their involvement in biological processes such as cellular energy production, oxidative metabolism, stress, protein synthesis, and protein folding. Furthermore, to better understand the expression pattern, signaling, and interaction events of spore proteins, we presented an interaction network using orthologous proteins from Ustilago maydis as a model. Most of the orthologous proteins that were identified in this study were not clustered in the network, but several of them play a very important role in hypha development and branching.

CONCLUSIONS

The quantities of basidiospores 7 × 10(9); 5.2 × 10(8), and 6.7 × 10(8) were sufficient to obtain enough protein mass for the three 2D-PAGE replicates, for the 0, 2, and 4 h-treatments, respectively. The protein extraction method that is based on sedimentation, followed by sonication with SDS-dense buffer, and phenolic extraction, which was utilized in this study, was effective, presenting a satisfactory resolution and reproducibility for M. perniciosa basidiospores. This report constitutes the first comprehensive study of protein expression during the ungerminated stage of the M. perniciosa basidiospore. Identification of the spots observed in the reference gel enabled us to know the main molecular interactions involved in the initial metabolic processes of fungal development.

Ambient pH stress inhibits spore germination of Penicillium expansum by impairing protein synthesis and folding: a proteomic-based study

Spore germination is the first step for fungal pathogens to infect host plants. The pH value, as one of the most important environmental parameters, has critical influence on spore germination. In this study, effects of ambient pH on spore germination were determined by culturing spores of Penicillium expansum in medium with pH values at 2.0, 5.0 and 8.0, and involved mechanisms were further investigated through methods of comparative proteomics. The results demonstrated that spore germination of P. expansum was obviously inhibited at pH 2.0 and 8.0. Using quadrupole time-of-flight tandem mass spectrometer, 34 proteins with significant changes in abundance were identified. Among them, 17 proteins were related to protein synthesis and folding, and most of them were down-regulated at pH 2.0 and 8.0. Accordingly, lower content of total soluble proteins and higher ratio of aggregated proteins were observed in spores at pH 2.0 and 8.0. In addition, it was found that ambient pH could affect intracellular pH and ATP level of P. expansum spores. These findings indicated that ambient pH might affect spore germination of P. expansum by changing intracellular pH and regulating protein expression. Further, impairing synthesis and folding of proteins might be one of the main reasons.

Proteomic profile of dormant Trichophyton rubrum conidia

Background

Trichophyton rubrum is the most common dermatophyte causing fungal skin infections in humans. Asexual sporulation is an important means of propagation for T. rubrum, and conidia produced by this way are thought to be the primary cause of human infections. Despite their importance in pathogenesis, the conidia of T. rubrum remain understudied. We intend to intensively investigate the proteome of dormant T. rubrum conidia to characterize its molecular and cellular features and to enhance the development of novel therapeutic strategies.

Results

The proteome of T. rubrum conidia was analyzed by combining shotgun proteomics with sample prefractionation and multiple enzyme digestion. In total, 1026 proteins were identified. All identified proteins were compared to those in the NCBI non-redundant protein database, the eukaryotic orthologous groups database, and the gene ontology database to obtain functional annotation information. Functional classification revealed that the identified proteins covered nearly all major biological processes. Some proteins were spore specific and related to the survival and dispersal of T. rubrum conidia, and many proteins were important to conidial germination and response to environmental conditions.

Conclusion

Our results suggest that the proteome of T. rubrum conidia is considerably complex, and that the maintenance of conidial dormancy is an intricate and elaborate process. This data set provides the first global framework for the dormant T. rubrum conidia proteome and is a stepping stone on the way to further study of the molecular mechanisms of T. rubrum conidial germination and the maintenance of conidial dormancy.

Analysis of the Aspergillus nidulans thaumatin-like cetA gene and evidence for transcriptional repression of pyr4 expression in the cetA-disrupted strain

The asexual spore or conidium plays a critical role in the life cycle of many filamentous fungi. However, the process of conidial germination remains surprisingly obscure. To better understand this process at the molecular level we characterized the Aspergillus nidulans cetA gene which is uniquely transcribed in conidiating cultures and whose transcript is significantly enriched in mature conidia. CetA is a member of a novel family of fungal genes of unknown function with homology to plant thaumatin-like (PR-5) defense proteins. We demonstrate by Northern analysis that cetA is a glucose-repressible gene. Transcriptional repression is dependent on the presence of protein kinase A. Western analysis indicates that the CETA protein is absent from conidia but is highly expressed during the first 6h of germination and is secreted into the medium. Disruption of the cetA gene seemingly results in delayed germination, slow growth, abnormal hyphal branching, and cell-wall defects. However, further analysis shows that the mutant phenotype is the result of glucose-dependent transcriptional repression of the pyr4 selectable marker used to disrupt the cetA gene. This is the first time that repression of a selectable marker ("position effect") has been reported in A. nidulans, a finding that may well be of significance in the analysis and interpretation of mutant phenotypes in this organism.

Impact of water-stress and washing treatments on production, synthesis and retention of endogenous sugar alcohols and germinability of Metarhizium anisopliae blastospores

The entomopathogenic fungus Metarhizium anisopliae was physiologically manipulated by culturing in liquid culture under a range of water-stress conditions (0.98, 0.97 and 0.96 water activity, a(w)) imposed by either PEG 200, KCl or NaCl at 25 degrees C to optimise blastospore production and quality in terms of accumulation of endogenous compatible solutes and germinability. Optimum spore yield occurred at 0.98a(w), when PEG 200 was the solute. Blastospores produced under different water-stress levels were subjected to hypo-osmotic and iso-osmotic washing treatments before quantification of endogenous sugar alcohols (polyols) and germinability studies. Endogenous amounts of the low molecular weight polyol erythritol were greatly affected by culture age, water-stress and hypotonic or isotonic washing treatment. Endogenous erythritol in blastospores produced under 0.98 and 0.97a(w) increased with culture age. Osmoprotection (washing with isotonic PEG 200 solution) of blastospores produced under all water-stress conditions resulted in retention of higher amounts of erythritol. Increased endogenous retention of the high molecular weight polyol mannitol was also observed with an isotonic washing treatment but only in blastospores produced under intermediate water-stress (0.98 and 0.97a(w)). Germination of all treatments was > 90 % on a medium with freely available water. Under water-stress conditions (0.96a(w)) only 10 % of unmodified blastospores washed with water germinated. However, those grown under modified water availability conditions (0.98a(w)) and washed with isotonic solutions had significantly improved germination (38-90 %). Blastospores produced at < or = 0.97a(w) washed with isotonic solutions had decreased germination. These results could have significant implications for conserving ecophysiological quality of fungal biocontrol propagules during harvesting and have an impact on storage and formulation.

Identification and quantitative expression analysis of genes that are differentially expressed during conidial germination in Pyrenophora teres

Net blotch, caused by Pyrenophora teres, is a common disease of barley ( Hordeum vulgareL.). Two PCR-based differential screening techniques, cDNA-amplified fragment length polymorphism (cDNA-AFLP) and suppression subtractive hybridisation (SSH), were employed to clone cDNA copies of transcripts that are up-regulated during conidial germination. The nucleotide sequences of 35 transcripts were analysed, and the amino acid sequences of their predicted products were compared with entries in databases. Eleven of these clones showed homology to genes from other ascomycetes coding for a transcription factor, two regulatory proteins, a putative transposase, a protein required for the biogenesis of cytochrome C oxidase, a threonine synthase, a probable subunit of a phenylalanine-tRNA synthetase, a subunit of RNA polymerase I, a cation transport protein, a vacuolar ATP synthase subunit, and an RNA processing protein. One conserved hypothetical protein was found and 23 sequences could not be functionally classified. The relative expression of five transcripts at 0, 1, 2, 3, 6, 12 and 24 h after induction of germination was determined by real-time RT-PCR using 18S rRNA as the endogenous reference sequence. All transcripts showed a significant increase in expression during early stages of germination. The maximum change in expression relative to ungerminated conidia ranged between 2.6- and 6-fold. The characterisation of genes involved in biochemical processes during the germination of conidia could be useful for target-specific development of new antifungal agents.

The molecular mechanisms of conidial germination

The asexual spore, or conidium, is critical in the life cycle of many fungi because it is the primary means for dispersion and serves as a 'safe house' for the fungal genome in adverse environmental conditions. This review discusses the physiological process of germination, conidial adhesion and initiation of protein synthesis and also the regulatory pathways used to activate conidial germination. These include Ca(2+)/calmodulin-mediated signaling, the cyclic AMP/protein kinase A and the ras/mitogen-activated protein kinase pathways. Insights into the process of conidial germination will increase our understanding of the mechanisms of dormancy and sensing of environmental stimuli, and permit identification of novel therapeutic targets for the treatment of spore-borne fungal infections in plants and animals.

Models of cell differentiation in conidial fungi

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