Classification of sequences expressed during the primordial and basidiome stages of the cultivated mushroom Agaricus bisporus

Comparative transcriptome analysis reveals potential fruiting body formation mechanisms in Morchella importuna

Morchella importuna has been artificially cultivated, but stable production remains difficult because its mechanisms of fruiting body formation are unclear. To investigate the fruiting body formation mechanisms, we sequenced the transcriptomes of Morchella importuna at the mycelial and young fruiting body stages. Among the 12,561 differentially expressed genes (DEGs), 9215 were upregulated, and 3346 were downregulated. DEG enrichment analysis showed that these genes were enriched in the "generation of precursor metabolites and energy", "carbohydrate catabolic process", and "oxidoreductase activity" Gene Ontology (GO) functional categories. Enzyme activity assay results indicated that the activity levels of CAZymes (carbohydrate-active enzymes), oxidoreductases (SOD (superoxide dismutase), CAT (catalase)) and mitochondrial complex (complex I, II, III) proteins were significantly increased from the mycelial stage to the young fruiting body stage. In addition, the genes encoding CAZymes, mitochondrial proteins, oxidoreductases and heat shock proteins had higher expression levels in the young fruiting body stage than in the mycelial stage, and the qRT-PCR results showed similar trends to the RNA-Seq results. In summary, these results suggest that carbohydrate catabolism and energy metabolism are significantly enhanced in the young fruiting body stage and that growth environment temperature changes affect the formation of fruiting bodies.

Comparative transcriptomics of Pleurotus eryngii reveals blue-light regulation of carbohydrate-active enzymes (CAZymes) expression at primordium differentiated into fruiting body stage

Blue light is an important environmental factor which could induce mushroom primordium differentiation and fruiting body development. However, the mechanisms of Pleurotus eryngii primordium differentiation and development induced by blue light are still unclear. The CAZymes (carbohydrate-active enzymes) play important roles in degradation of renewable lignocelluloses to provide carbohydrates for fungal growth, development and reproduction. In the present research, the expression profiles of genes were measured by comparison between the Pleurotus eryngii at primordium differentiated into fruiting body stage after blue light stimulation and dark using high-throughput sequencing approach. After assembly and compared to the Pleurotus eryngii reference genome, 11,343 unigenes were identified. 539 differentially expressed genes including white collar 2 type of transcription factor gene, A mating type protein gene, MAP kinase gene, oxidative phosphorylation associated genes, CAZymes genes and other metabolism related genes were identified during primordium differentiated into fruiting body stage after blue light stimulation. KEGG results showed that carbon metabolism, glycolysis/gluconeogenesis and biosynthesis of amino acids pathways were affected during blue light inducing primordia formation. Most importantly, 319 differentially expressed CAZymes participated in carbon metabolism were identified. The expression patterns of six representative CAZymes and laccase genes were further confirmed by qRT-PCR. Enzyme activity results indicated that the activities of CAZymes and laccase were affected in primordium differentiated into fruiting body under blue light stimulation. In conclusion, the comprehensive transcriptome and CAZymes of Pleurotus eryngii at primordium differentiated into fruiting body stage after blue light stimulation were obtained. The biological insights gained from this integrative system represent a valuable resource for future genomic studies on this commercially important mushroom.

The first set of expressed sequence tags (EST) from the medicinal mushroom Agaricus subrufescens delivers resource for gene discovery and marker development

Agaricus subrufescens is one of the most important culinary-medicinal cultivable mushrooms with potentially high-added-value products and extended agronomical valorization. The development of A. subrufescens-related technologies is hampered by, among others, the lack of suitable molecular tools. Thus, this mushroom is considered as a genomic orphan species with a very limited number of available molecular markers or sequences. To fill this gap, this study reports the generation and analysis of the first set of expressed sequence tags (EST) for A. subrufescens. cDNA fragments obtained from young sporophores (SP) and vegetative mycelium in liquid culture (CL) were sequenced using 454 pyrosequencing technology. After assembly process, 4,989 and 5,125 sequences were obtained in SP and CL libraries, respectively. About 87% of the EST had significant similarity with Agaricus bisporus-predicted proteins, and 79% correspond to known proteins. Functional categorization according to Gene Ontology could be assigned to 49% of the sequences. Some gene families potentially involved in bioactive compound biosynthesis could be identified. A total of 232 simple sequence repeats (SSRs) were identified, and a set of 40 EST-SSR polymorphic markers were successfully developed. This EST dataset provides a new resource for gene discovery and molecular marker development. It constitutes a solid basis for further genetic and genomic studies in A. subrufescens.

Para-aminobenzoic acid (PABA) synthase enhances thermotolerance of mushroom Agaricus bisporus

Most mushrooms are thermo-sensitive to temperatures over 23°C, which greatly restricts their agricultural cultivation. Understanding mushroom’s innate heat-tolerance mechanisms may facilitate genetic improvements of their thermotolerance. Agaricus bisporus strain 02 is a relatively thermotolerant mushroom strain, while strain 8213 is quite thermo-sensitive. Here, we compared their responses at proteomic level to heat treatment at 33°C. We identified 73 proteins that are differentially expressed between 02 and 8213 or induced upon heat stress in strain 02 itself, 48 of which with a known identity. Among them, 4 proteins are constitutively more highly expressed in 02 than 8213; and they can be further upregulated in response to heat stress in 02, but not in 8213. One protein is encoded by the para-aminobenzoic acid (PABA) synthase gene Pabs, which has been shown to scavenge the reactive oxygen species in vitro. Pabs mRNA and its chemical product PABA show similar heat stress induction pattern as PABA synthase protein and are more abundant in 02, indicating transcriptional level upregulation of Pabs upon heat stress. A specific inhibitor of PABA synthesis impaired thermotolerance of 02, while exogenous PABA or transgenic overexpression of 02 derived PABA synthase enhanced thermotolerance of 8213. Furthermore, compared to 8213, 02 accumulated less H₂O₂ but more defense-related proteins (e.g., HSPs and Chitinase) under heat stress. Together, these results demonstrate a role of PABA in enhancing mushroom thermotolerance by removing H₂O₂ and elevating defense-related proteins.

Agaricus bisporus genome sequence: a commentary

The genomes of two isolates of Agaricus bisporus have been sequenced recently. This soil-inhabiting fungus has a wide geographical distribution in nature and it is also cultivated in an industrialized indoor process ($4.7bn annual worldwide value) to produce edible mushrooms. Previously this lignocellulosic fungus has resisted precise econutritional classification, i.e. into white- or brown-rot decomposers. The generation of the genome sequence and transcriptomic analyses has revealed a new classification, 'humicolous', for species adapted to grow in humic-rich, partially decomposed leaf material. The Agaricus biporus genomes contain a collection of polysaccharide and lignin-degrading genes and more interestingly an expanded number of genes (relative to other lignocellulosic fungi) that enhance degradation of lignin derivatives, i.e. heme-thiolate peroxidases and β-etherases. A motif that is hypothesized to be a promoter element in the humicolous adaptation suite is present in a large number of genes specifically up-regulated when the mycelium is grown on humic-rich substrate. The genome sequence of A. bisporus offers a platform to explore fungal biology in carbon-rich soil environments and terrestrial cycling of carbon, nitrogen, phosphorus and potassium.

Expression of phenol oxidase and heat-shock genes during the development of Agaricus bisporus fruiting bodies, healthy and infected by Lecanicillium fungicola

The fungal pathogen Lecanicillium fungicola (formerly Verticillium fungicola) is responsible for severe losses worldwide in the mushroom (Agaricus bisporus) industry. Infected crops are characterised by masses of undifferentiated tissue (bubbles) growing in place of sporophores. The expression of three laccase genes (lcc1, lcc2 and lcc3), two tyrosinase genes (AbPPO1 and AbPPO2) and the hspA gene encoding a heat-shock protein known to be potentially associated with host-pathogen interaction was investigated in mycelial aggregates and during the development of healthy sporophores and bubbles of a susceptible cultivar. The lcc3, AbPPO2 and hspA genes were each expressed at different levels at the different stages of sporophore morphogenesis, whilst they showed a stable expression throughout bubble development. The transcript levels were similar in bubbles and at the first developmental stage of healthy fruiting bodies, both showing no tissue differentiation. These observations suggest that lcc3, AbPPO2 and hspA are associated with A. bisporus morphogenesis. Comparing the expression of the hspA gene in three susceptible and three tolerant strains showed that the latter displayed a higher level of transcript in the primordium, which is the stage receptive to the pathogen. The six strains exhibited a comparable expression in the vegetative mycelium, non-receptive to L. fungicola.

Gene expression profiling of a Zn-tolerant and a Zn-sensitive Suillus luteus isolate exposed to increased external zinc concentrations

Complementary DNA (cDNA)-amplified fragment-length polymorphism (AFLP) was applied to analyze transcript profiles of a Zn-tolerant and a Zn-sensitive isolate of the ectomycorrhizal basidiomycete Suillus luteus, both cultured with and without increased external zinc concentrations. From the obtained transcript profiles that covered approximately 2% of the total expected complement of genes in S. luteus, 144 nonredundant, differentially expressed transcript-derived fragments (TDFs), falling in different classes of expression pattern, were isolated and sequenced. Thirty-six of the represented genes showed homology to function-known genes, whereas 6 matched unknown protein coding sequences, and 102 were possibly novel. Although relatively few TDFs were found to be responsive to the different zinc treatments, their modulated expression levels may suggest a different transcriptional response to zinc treatments in both isolates. Among the identified genes that could be related to heavy-metal detoxification or the tolerance trait were genes encoding for homologues of a heat-shock protein, a putative metal transporter, a hydrophobin, and several proteins involved in ubiquitin-dependent proteolysis.

Genetic linkage map and expression analysis of genes expressed in the lamellae of the edible basidiomycete Pleurotus ostreatus

Pleurotus ostreatus is an industrially cultivated basidiomycete with nutritional and environmental applications. Its genome contains 35 Mbp organized in 11 chromosomes. There is currently available a genetic linkage map based predominantly on anonymous molecular markers complemented with the mapping of QTLs controlling growth rate and industrial productivity. To increase the saturation of the existing linkage maps, we have identified and mapped 82 genes expressed in the lamellae. Their manual annotation revealed that 34.1% of the lamellae-expressed and 71.5% of the lamellae-specific genes correspond to previously unknown sequences or to hypothetical proteins without a clearly established function. Furthermore, the expression pattern of some genes provides an experimental basis for studying gene regulation during the change from vegetative to reproductive growth. Finally, the identification of various differentially regulated genes involved in protein metabolism suggests the relevance of these processes in fruit body formation and maturation.

Isolation and analysis of genes specifically expressed during fruiting body development in the basidiomycete Flammulina velutipes by fluorescence differential display

Using fluorescence differential display, cDNAs specifically expressed at the primordial stage of fruiting body development were isolated from the basidiomycete, Flammulina velutipes. Seventy-five cDNAs were sequenced and compared with the amino-acid sequences of proteins in the database by BLASTX search. Significant similarity was found for 29 cDNAs coding for proteins with known function, GTP-binding protein, growth factor, ubiquitin-proteasome, cytochrome P450 and hydrophobin, all of which would be associated with fruiting body development. Seventeen cDNAs were not similar to proteins in the database and may represent unique genes that play specific roles in the process of fruiting in F. velutipes.

Expressed sequence tag analysis of the soybean rust pathogen Phakopsora pachyrhizi

Soybean rust is caused by the obligate fungal pathogen Phakopsora pachyrhizi Sydow. A unidirectional cDNA library was constructed using mRNA isolated from germinating P. pachyrhizi urediniospores to identify genes expressed at this physiological stage. Single pass sequence analysis of 908 clones revealed 488 unique expressed sequence tags (ESTs, unigenes) of which 107 appeared as multiple copies. BLASTX analysis identified 189 unigenes with significant similarities (Evalue<10(-5)) to sequences deposited in the NCBI non-redundant protein database. A search against the NCBI dbEST using the BLASTN algorithm revealed 32 ESTs with high or moderate similarities to plant and fungal sequences. Using the Expressed Gene Anatomy Classification, 31.7% of these ESTs were involved in primary metabolism, 14.3% in gene/protein expression, 7.4% in cell structure and growth, 6.9% in cell division, 4.8% in cell signaling/cell communication, and 4.8% in cell/organism defense. Approximately 29.6% of the identities were to hypothetical proteins and proteins with unknown function.

Transcript profiling reveals novel marker genes involved in fruiting body formation in Tuber borchii

cDNA arrays were used to explore mechanisms controlling fruiting body development in the truffle Tuber borchii. Differences in gene expression were higher between reproductive and vegetative stage than between two stages of fruiting body maturation. We suggest hypotheses about the importance of various physiological processes during the development of fruiting bodies.

Differential expression of a putative riboflavin-aldehyde-forming enzyme (raf) gene during development and post-harvest storage and in different tissue of the sporophore in Agaricus bisporus

Cloning and characterisation of a putative riboflavin-aldehyde-forming enzyme gene (raf) from the cultivated mushroom Agaricus bisporus and its expression during morphogenesis are described. Three cDNA clones were isolated following differential screening of cDNA libraries from rapidly expanding sporophores and post-harvest stored sporophores. The cDNA sequence and predicted translation analysis revealed an open reading frame (ORF) of 348 nucleotides encoding a polypeptide of 115 amino acids, with three introns (56-66 bases) interrupting the genomic ORF. Blast X searches of the databases with the gene sequence showed homology (40% identity and 56% similarity) to the riboflavin-aldehyde-forming enzyme gene from Schizophyllum commune. In A.bisporus, the raf gene sequence upstream of the ORF contained a large CT-rich putative regulatory element (-64 to -24 bases) found in highly expressed genes in various mushrooms, and a 6-base motif present in the 3' end of the genomic sequence, but not in the corresponding 3' non-coding part of the cDNA, was identified. The raf gene transcripts increased abundantly in rapidly developing sporophores as well in post-harvest stored sporophores. Differential expression of the raf gene transcripts in different tissues of the sporophore was also observed, with higher levels in the stipe compared with the cap and gills. The temporal and spatial expression patterns observed suggest transcriptional regulation of the raf gene during A. bisporus morphogenesis.

Molecular cloning of developmentally specific genes by representational difference analysis during the fruiting body formation in the basidiomycete Lentinula edodes

To understand molecular mechanisms of the fruiting body development in basidiomycetes, we attempted to isolate developmentally regulated genes expressed specifically during the fruiting body formation of Lentinula edodes (Shiitake-mushroom). cDNA representational difference analysis (cDNA-RDA) between vegetatively growing mycelium and two developmental substages, primordium and mature fruiting body, resulted in an isolation of 105 individual genes (51 in primordium and 54 in mature fruiting body, respectively). A search of homology with the protein databases and two basidiomycetous genomes in Phanerochaete chrysosporium and Coprinopsis cinerea revealed that the obtained genes encoded various proteins similar to those involved in general metabolism, cell structure, signal transduction, and responses to stress; in addition, there were apparently several metabolic pathways and signal transduction cascades that could be involved in the fruiting body development. The expression products of several genes revealed no significant homologies to those in the databases, implying that those genes are unique in L. edodes and the encoding products may possess possible functions in the course of fruiting body development. RT-PCR analyses revealed that 20 candidates of the obtained genes were specifically or abundantly transcribed in the course of the fruiting body formation, suggesting that the obtained genes in this work play roles in fruiting body development in L. edodes.

Cloning and developmental expression of a metzincin family metalloprotease cDNA from oyster mushroom Pleurotus ostreatus

A cDNA clone, PoMTP, encoding a putative metzincin family metalloprotease was isolated from the expressed sequence tags of a basidiomycete Pleurotus ostreatus. The 5'-end sequence of PoMTP was determined by the 5'-RACE method. Full-length cDNA sequence (1140 bp) of PoMTP contained a 870 bp open reading frame encoding a protein product of 290 amino acids in addition to a 99 bp of 5'-untranslated sequence and a 171 bp of 3'-untranslated sequence with a poly(A) tail. The deduced amino-acid sequences of PoMTP contained an extensive zinc-binding consensus sequence and a so-called Met-turn sequence which are typical for the metzincin family of metalloproteases, indicating that the PoMTP protein belongs to the metzincin metalloproteases. Four cysteine residues were also observed in the zinc-binding region of PoMTP amino-acid sequence, which are known to be important for the structure and the function of some subfamilies of the metzincins. Comparison of the PoMTP in sequence database showed no significant homology with functionally known metalloproteases of Armillaria mellea, Grifola frondosa, Lentinula edodes, Pleurotus ostreatus, Schizophyllum commune and Tricholoma saponaceum in mushroom. Northern blot and qunatitative RT-PCR analyses indicated the PoMTP mRNA to be abundant at primordial and fruit body stages, but scarce at the mycelial stage, suggesting that the PoMTP metalloprotease plays an important role in mushroom fruiting.

Interaction of Sclerotinia sclerotiorum with a resistant Brassica napus cultivar: expressed sequence tag analysis identifies genes associated with fungal pathogenesis

Sclerotinia sclerotiorum is a ubiquitous necrotrophic fungal pathogen capable of infecting a wide range of plants. To identify genes involved in fungal development and pathogenesis we generated 2232 expressed sequence tags (ESTs) from two cDNA libraries constructed using either mycelia grown in pectin medium or tissues from infected Brassica napus stems. A total of 774 individual fungal genes were identified of which 39 were represented only among the infected plant EST collection. Annotation of 534 unigenes was possible following the categories applied to Saccharomyces cerevisiae and the Universal Gene Ontology scheme. cDNAs were identified that encoded potential pathogenicity factors including four endopolygalacturonases, two exopolygalacturonases, and several metabolite transporters. The potential role of these genes, as well as those encoding signal transduction factors, in the infection process is discussed.

Comparative gene expression in the symbiotic and aposymbiotic Aiptasia pulchella by expressed sequence tag analysis

Intracellular symbiotic relationships are prevalent between cnidarians, such as corals and sea anemones, and the photosynthetic dinoflagellate symbionts. However, there is little understanding about how the genes express when the symbiotic relationship is set up. To characterize genes involved in this association, the endosymbiosis between sea anemone, Aiptasia pulchella, and dinoflagellate zooxanthellae, Symbiodinium spp., was employed as a model. Two complementary DNA (cDNA) libraries were constructed from RNA isolated from symbiotic and aposymbiotic A. pulchella. Using single-pass sequencing of cDNA clones, a total of 870 expressed sequence tags (ESTs) clones were generated from the two libraries: 474 from symbiotic animal and 396 from aposymbiotic animal. The initial ESTs consisted of 143 clusters and 231 singletons. A BLASTX search revealed that 147 unique genes had similarities with protein sequences available from databases; 120 of these clones were categorized according to their putative function. However, many ESTs could not assign functionally. The putative roles of some of the identified genes relative to endosymbiosis were discussed. This is the first report of the use of EST analysis to examine the gene expression in symbiotic and aposymbiotic states of the cnidarians. The systematic analysis of EST from this study provides a useful database for future investigations of the molecular mechanisms involved in algal-cnidarian symbiosis.

Gene expression and EST analyses of Ustilago maydis germinating teliospores

Ustilago maydis grows in its host Zea mays eliciting the formation of obvious tumors that are full of black teliospores. Teliospores are thick-walled, dormant, diploid cells that have evolved for dispersal and survival of the pathogen. Their germination leads to new rounds of infection and is temporally linked to meiosis. We are investigating gene expression during teliospore germination to gain insight into the control of this process. Here we identify genes expressed through creation of an expressed sequence tag (EST) library. We generated 2871 ESTs that are assembled into 1293 contiguous sequences. Based upon a blast search similarity cutoff of E < or =10(-5) 38% of all contigs were orphans while 62% showed similarity to sequences in the protein database. Analyses of blast searches were used to functionally classify genes. Northern hybridizations using specific cDNA clones reveal a relative level of expression consistent with the number of sequences per contig. Identified genes and expression information provide a base for genome annotation of U. maydis and further investigation of teliospore germination and pathogenesis.

The Aa-Pri4 gene, specifically expressed during fruiting initiation in the Agrocybe aegerita complex, contains an unusual CT-rich leader intron within the 5' uncoding region

The Aa1-Pri4 gene was cloned from the edible mushroom Agrocybe aegerita. The gene, specifically expressed during fruiting initiation, encodes a glycine-rich protein of 116 amino acids, with no homology to already known proteins. Homologous genes were amplified from two other strains belonging to the Agr. aegerita complex and originating from South-East Asia; and a comparison of the three genes revealed a high conservation of the coding sequences (72.8-97.8%). The PRI4 putative protein sequences were highly similar (87.5-100.0%); and all of them contained two protein kinase C sites, suggesting a potential supplementary regulation by phosphorylation at the protein level. The 5' uncoding regions all presented a leader intron, very variable in sequence (45.7% identity), but with a high C+T content (74.5-79.0%). The presence of such CT-rich sequences previously described in the promoter of highly expressed fungal genes suggests that the leader intron of the Aa1-Pri4 gene could be involved in the high-level, stage-specific expression.

Analysis of expressed sequence tags from the ectomycorrhizal basidiomycetes Laccaria bicolor and Pisolithus microcarpus

•  In an effort to discover genes that are expressed in the ectomycorrhizal basidiomycetes Laccaria bicolor and Pisolithus microcarpus, and in P. microcarpus/Eucalyptus globulus ectomycorrhizas, we have sequenced 1519 and 1681 expressed sequence tags (ESTs) from L. bicolor and P. microcarpus cDNA libraries. •  Contig analysis resulted in 905 and 806 tentative consensus sequences (unique transcripts) in L. bicolor and P. microcarpus, respectively. For 36% of the ESTs, significant similarities to sequences in databases were detected. The most abundant transcripts showed no similarity to previously identified genes. Sequence redundancy analysis between different developmental stages indicated that several genes were differentially expressed in free-living mycelium and symbiotic tissues of P. microcarpus. •  Based on sequence similarity, 11% of L. bicolor unique transcripts were also detected in P. microcarpus. Similarly, L. bicolor and P. microcarpus shared only a low proportion of common transcripts with other basidiomycetous fungi, such as Pleurotus ostreatus and Agaricus bisporus. Such a low proportion of shared transcripts between basidiomycetes suggests, on the one hand, that the variability of expressed transcripts in different fungi and fungal tissues is considerably high. On the other hand, it might reflect the low number of GenBank entries of basidiomycetous origin and stresses the necessity of an additional sequencing effort. •  The present ESTs provide a valuable resource for future research on the development and functioning of ectomycorrhizas.

ESTs from the basidiomycete Schizophyllum commune grown on nitrogen-replete and nitrogen-limited media

Lambda phage cDNA libraries were constructed using mRNAs from the basidiomycete Schizophyllum commune grown on media with high or low nitrogen concentrations. A total of 440 clones were sequenced, representing 373 distinct transcripts. Of these, 166 showed significant similarity to annotated genes in GenBank. Those that could be tentatively identified using BLAST searches were classified by function using the Gene Ontology (GO) database. Genes with products involved in cell-cycle processes were more frequent in the nitrogen-limited libraries, while genes with products involved in protein biosynthesis were more frequent in the nitrogen-replete library. Overall, clones showed much greater similarity to the one publicly available basidiomycete genome, Phanerochaete chrysosporium, than to any of the ascomycete genomes.

Analysis of expressed sequence tags from Gibberella zeae (anamorph Fusarium graminearum)

Gibberella zeae is a broad host range pathogen that infects many crop plants, including wheat and barley, and causes head blight and rot diseases throughout the world. To better understand fungal development and pathogenicity, we have generated 7996 ESTs from three cDNA libraries. Two libraries were generated from carbon-(C-) and nitrogen- (N-) starved mycelia and one library was generated from cultures of maturing perithecia (P). In other fungal pathogens, starvation conditions have been shown to act as cues to induce infection-related gene expression. To assign putative function to cDNAs, sequences were initially assembled using StackPack. The estimated total number of genes identified from the three EST databases was 2110: 1088 contigs and 1022 singleton sequences. These 2110 sequences were compared to a yeast protein sequence reference set and to the GenBank nonredundant database using BLASTX. Based on presumptive gene function identified by this process, we found that the two starved cultures had similar, but not identical, patterns of gene expression, whereas the developmental cultures were distinct in their pattern of expression. Of the three libraries, the perithecium library had the greatest percentage (46%) of ESTS falling into the "unclassified" category. Homologues of some known fungal virulence or pathogenicity factors were found primarily in the N- and C-libraries. Comparisons also were made with ESTs from the related fungi, Neurospora crassa and Magnaporthe grisea and the genomic sequence of N. crassa.

Comparative analysis of sequences expressed during the liquid-cultured mycelia and fruit body stages of Pleurotus ostreatus

To characterize genes involved in fruit body development, two complementary DNA (cDNA) libraries were constructed from RNA isolated from liquid-cultured mycelia and fruit bodies of Pleurotus ostreatus. Using single-pass sequencing of cDNA clones, 952 and 1069 expressed sequence tags (ESTs) were generated from liquid-cultured mycelia and fruit body cDNA library, respectively. A BLASTX search revealed that 390 of the liquid-cultured mycelia ESTs (41%) and 531 of the fruit body ESTs (50%) showed significant similarity to protein sequences described in the nonredudant database (E values < or =1 x 10(-5)). When liquid-cultured mycelia and fruit body ESTs were compared by the SeqMan II program, among the total of 2021 ESTs, 1256 ESTs were unigenes, and 66 unigenes (5.3%) were commonly expressed during both stages. The functional catalogs of the ESTs were made by comparison with functionally identified Saccharomyces cerevisiae genes. Liquid-cultured mycelium ESTs were compared with fruit body ESTs and changes of the expressed genes during fruit body development were analyzed.

Characterization of the Aspergillus nidulans septin (asp) gene family

Members of the septin gene family are involved in cytokinesis and the organization of new growth in organisms as diverse as yeast, fruit fly, worm, mouse, and human. Five septin genes have been cloned and sequenced from the model filamentous fungus A. nidulans. As expected, the A. nidulans septins contain the highly conserved GTP binding and coiled-coil domains seen in other septins. On the basis of hybridization of clones to a chromosome-specific library and correlation with an A. nidulans physical map, the septins are not clustered but are scattered throughout the genome. In phylogenetic analysis most fungal septins could be grouped with one of the prototypical S. cerevisiae septins, Cdc3, Cdc10, Cdc11, and Cdc12. Intron-exon structure was conserved within septin classes. The results of this study suggest that most fungal septins belong to one of four orthologous classes.

Differential expression of chitin synthase III and IV mRNAs in ascomata of Tuber borchii Vittad

A full-length genomic clone encoding a class III chitin synthase (CHS) and one DNA fragment corresponding to a class IV CHS were isolated from the mycorrhizal fungus Tuber borchii and used for an extensive expression analysis, together with a previously identified DNA fragment corresponding to a class II CHS. All three Chs mRNAs are constitutively expressed in vegetative mycelia, regardless of the age, mode of growth, and proliferation capacity of the hyphae. A strikingly different situation was observed in ascomata, where class III and IV, but not class II, mRNAs are differentially expressed in a maturation stage-dependent manner and accumulate, respectively, in sporogenic and vegetative hyphae. These data, the first on the expression of distinct Chs mRNAs during fruitbody development, point to the different cellular roles that can be played by distinct chitin synthases in the differentiation of spores of sexual origin (CHS III) or in ascoma enlargement promoted by the growth of vegetative hyphae (CHS IV).