The impact of loci that determine sexual identity upon the asexual, dominant stage of Asexual lifestyle support groups in ct life history has been well studied.
To investigate their impact, expression differences between strains of different mating type during asexual development were assayed, with RNA sampled from otherwise largely isogenic mat A and mat a strains of Neurospora crassa at early, middle, and late clonal stages of development. We observed significant differences in overall gene expression between mating types across clonal development, especially at late development stages.
The expression levels of mating-type genes and pheromone genes were assayed by reverse transcription and quantitative PCR, revealing expression of pheromone and receptor genes instrains of both mating types in all development stages, and revealing that mating type mat genes were increasingly expressed over the course of asexual development.
Interestingly, among differentially expressed genes, the mat A genotype more frequently exhibited a higher expression level than mat aand demonstrated greater transcriptional regulatory dynamism. Significant up-regulation of expression was observed for many late light-responsive genes at late asexual development stages.
Further investigation of the impact of light and the roles of light response genes in asexual development of both mating types are warranted. The genetics of sexual identity in most fungi are conferred by mating-type loci that exhibit diversity in size, number, and sequence among different fungal groups Lee et al.
The function of mating-type genes has been intensively studied in fungal models during crossing and sexual development Glass and Lee, ; Saupe et al. However, vegetative stages of the life cycle, encompassing hyphal growth, branching, anastomosis, and asexual sporulation, are generally dominant in fungal life histories. In general, fungal mating type is not considered to have a significant impact on the growth or phenotypic characteristics of individuals Coppin et al.
Nevertheless, an association between mating type and fungal pathogenicity has been demonstrated Kolmer and Ellingboe, ; Funnell et al. Furthermore, in Neurosporaa superiority in perithecial production of mating-type a mat a strains was observed in both intraspecific and interspecific crosses Dettman et al. Recently, regulation of mating types on their target genes were investigated using genome wide gene expression profiling for heterothallic fungus Podospora anserinaand mating-type transcription factors were found to have impact on genes not directly related to mating in P.
Although genome-wide transcriptional profiling in N. Further characterization of gene expression associated with mating type in N. In the heterothallic model fungus N.
The genes of the "Asexual lifestyle support groups in ct" A idiomorph encode three proteins: Knockout strains of mat loci also show no morphological differences from wild-type in N.
Nevertheless, pheromone genes are maintained in the genomes of true homothallic fungi like Neurospora africanaSordaria macrosporaand Anixiella sublineolataand are expressed in the asexual life cycle of N. Although mat genes are undergoing genetic decay in some homothallic species, including N. Perhaps in part due to Asexual lifestyle support groups in ct understood pleiotropic functions, previous studies have revealed conflicting results with regard to the expression of pheromone precursors in strains of different mating types.
Pheromone precursor gene mfa-1 has been attributed specific function only in mat ayet it can be detected at a low expression level in mat A tissues Kim et al. The functions of N. However, their functions during pre-mating asexual development are not clear. In the recent studies of Podospora Asexual lifestyle support groups in ct and Sordaria macrosporamating type specific expression was observed for genes with diverse function, includingmetabolism, information pathways, transport, and developmental processes Bidard et al.
However, these studies focused on crossing and sexual development, and no core genes active in asexual development, such as the cell division cycle genes cdcconidiation genes conand heat shock protein genes hspwere found differently expressed between Asexual lifestyle support groups in ct types.
During asexual development, these genes are of critical function, and regulation of many these genes, including clock-controlled genes ccg and con genes, has not been well understood.
In most organisms, circadian oscillators regulate the rhythmic expression of ccgsand the two best characterized ccgs in Neurospora are ccg-1 and ccg-2known as morning-specific genes. Whilethe precise function of ccg-1which is conserved among filamentous fungi and can be induced by heat shock, is elusive, the gene ccg-2 encodes a secreted hydrophobic protein belonging to the hydrophobins, "Asexual lifestyle support groups in ct" coat the outer cell wall of fungi and maintain the cell-surface hydrophobicity for air dispersal of mature conidiospores Bell-Pedersen et al.
The production and release of conidiospores in fungi is also subject to the circadian clock, and daily rhythms in spore development and spore discharge are common in fungi Bell-Pedersen et al. At least four con genes, including con-6con-8conand conare known to be expressed during development of three types of spores in N.
Nevertheless, disruption of these genes does not cause a discernible phenotype in spore morphology, abundance of spores, conidial germination efficiency, nor ability to function as either parent in sexual crosses Springer and Yanofsky, ; Springer, In this study, we investigated the global expression differences between largely isogenic strains of different mating type.
Mating-type specific expression of genes was quantified using genomic microarrays.
The minimal differences in genetic background between highly isogenic mating types provided a straightforward system for investigating transcriptomic shifts of metabolic and regulatory function during morphological development. To maintain a controlled environment for investigating asexual development, the light-induced internal oscillator of N. Even under such controlled constant-light conditions, nominally light-responsive genes continue to play a central role in fungal development, so we investigated the behavior of light responsive genes Chen et al.
Furthermore, we performed reverse transcription and quantitative polymerase chain reaction RT-qPCR to determine, for the first time, expression of mat genes, the pheromone precursor genes ccg-4 and mfa-1and the receptor genes pre-1 and pre-2 at different stages of clonal development in N.
FGSC was derived from a long series of recurrent backcrosses to strain FGSCand is generally regarded as highly isogenic to the latter Mylyk et al.