Project description:Fungi exhibit a huge diversity in morphology and ecology, and genetic basis of morphological development in sexual reproduction of multi-cellular fungi has not been fully investigated with genome-wide approaches. Model organism Neurospora crassa is the very first sequenced genome for multi-cellular fungi, and well-annotated genome and gene markers characterized for key morphological traits make N. crassa an ideal platform to investigate transcriptome and its regulation during sexual development. RNA sequencing with different priming strategies have been efficient to provide fine-scale transcriptome landscapes for a multiple-staged development process. RNA were sampled for eight time points cross perithecial development, including two points right before and after crossing, for which mat A protoperithecia were fertilized with mat a conidia. Transcription profiles for 9717 genes were achieved for all eight time-points using multi-targeting priming and additional 14 genes for five time-points using random hexmas priming. Majority of the genome showed continually up- or down- regulated expression patterns during the later perithecial development stages after 72 or 96 h. Functionally unclassified proteins were counted for most up-regulated genes, while genes were enriched with different functions for different down-regulation patterns. We observed significant increase in transcription for mat a-1 and for mat A-1 specific pheromone precursor ccg-4 during the perithecial development, and expression of genetic markers for morphological traits in perithecium, ascus, and ascospore, and for development traits in meiosis often showed multiple peaks during the experiment. We also observed different expression patterns in transcription for other transcription factors and for genes involved in Meiotic Silencing and Repeat Induced Point Mutation, and expression of a gene encoding a protein similar to stc-1 in fission yeast, was increased after crossing and reached almost 1000 fold changes at 144h. Different expression patterns were also observed for genes involved in heterokaryotic and vegetative incompatibility and for genes functioning in the heterotrimmeric G protein signalling systems and in the MAP kinase signalling pathways. By sequencing RNAs from different development stages with two priming strategies, this study provided a large amount of data to quantifiably describe the sophisticated transcriptomic landscape in pre-mating, crossing and sexual reproduction of N. crassa. As major expression patterns for genes in different function categories were recognized during this process, our results in general supported previous observation of expression patterns for genetic markers and regulatory genes/pathway. This study provided further evidence for functional correlation among genes involved in same function or pathways, which included mating type genes and pheromones, transcription factors, pigmentation, heterokaryotic incompatibility, singaling pathways, and RNA silencing. Besides, we also disclosed different expression patterns for the regulatory genes/pathways cross the whole sexual development, and functions of some of these genes were also suggested with phenotypic studies of knockouts. Understanding how these different regulatory elements and their function networks adjust genome-wide transcriptomic and proteomic expression will provide detailed insights about morphological development of tissue-differentiated perithecia in N. crassa. RNA were sampled for eight time points cross perithecial development, including two points right before and after crossing, for which mat A protoperithecia were fertilized with mat a conidia. Two priming MTP and N6 were used separately as technique replicates for the first strain synthesis during cDNA preparation of all samples. Total 16 cDNAs were sequenced

Project description:Fusarium graminearum and F. verticillioides are devastating cereal pathogens with very different life history and ecological characteristics. F. graminearum is homothallic, and sexual spores are an important component of its life cycle, responsible for disease initiation. F. verticilloides is heterothallic, and produces only modest numbers of fruiting bodies, which are not a significant source of inoculum. To identify corresponding differences in the transcriptional program underlying fruiting body development in the two species, comparative expression was performed, analyzing six developmental stages. To accompany the transcriptional analysis, detailed morphological characterization of F. verticillioides development was performed and compared to a previous morphological analysis of F. graminearum. Morphological development was similar between the two species, except for the observation of possible trichogynes in F. verticillioides ascogonia, which have not been previously reported for any Fusarium species. Expression of over 9000 orthologous genes were measured for the two species. Functional assignments of highly expressed orthologous genes at each time-point revealed the majority of highly expressed genes fell into the M-bM-^@M-^XM-bM-^@M-^Xunclassified proteinsM-bM-^@M-^YM-bM-^@M-^Y category, reflecting the lack of characterization of genes for sexual development in both species. Simultaneous examination of morphological development and stage-specific gene expression suggests that degeneration of the paraphyses during sexual development is an apoptotic process. Expression of mating type genes in the two species differed, possibly reflecting the divergent roles they play in sexual development. Overall, the differences in gene expression reflect the greater role of fruiting bodies in the life cycle and ecology of F. graminearum versus F. verticillioides. mRNA were sampled and compared from six time points across sexual reproduction in two Fusarium species

Project description:Fungal fruiting body size and form are influenced by the ecology of the species, including diverse environmental stimuli. Accordingly, nutritional resources available to the fungus during development can be vital to successful production of fruiting bodies. To investigate the effect of nutrition, perithecial development of N. crassa was induced on two different media, a sparsely nutritive Synthetic Crossing Medium (SCM) and a natural Carrot Agar (CA). Protoperithecia were collected before crossing, and perithecia were collected at 2, 24, 48, 72, 96, 120, and at full maturity 144 hours after crossing. No differences in fruiting body morphology were observed between the two media at any time point. A circuit of microarray hybridizations comparing cDNA from all neighboring stages was performed. For a majority of differentially expressed genes, expression was higher in SCM than in CA, and expression of core metabolic genes was particularly affected. Effects of nutrition were highest in magnitude before crossing, lowering in magnitude during early perithecial development. Interestingly, metabolic effects of the media were also large in magnitude during late perithecial development, at which stage the lower expression in CA presumably reflected the continued intake of diverse complex initial compounds, diminishing the need for expression of anabolic pathways. However, for genes with key regulatory roles in sexual development, including pheromone precursor ccg-4 and poi2, expression patterns were similar between treatments. When possible, a common nutritional environment is ideal for comparing transcriptional profiles between different fungi. Nevertheless, the observed consistency of the developmental program across media, despite considerable metabolic differentiation is reassuring. This result facilitates comparative studies that will require different nutritional resources for sexual development in different fungi. Neurospora crassa mat A FGSC#2489 and mat-a FGSC 4200: Eight perithecial developmental stages, 0hr, 2 hr, 24 hr, 48 hr, 72 hr, 96 hr, 120 hr, and 144 hr were sampled and compared

Project description:Many fungi form complex three-dimensional fruiting bodies, within which the meiotic machinery for sexual spore production has been considered to be largely conserved over evolutionary time. Indeed, much of what we know about meiosis in plant and animal taxa has been deeply informed by studies of meiosis in Saccharomyces and Neurospora. Nevertheless, the genetic basis of fruiting body development and its regulation in relation to meiosis in fungi is barely known, even within the best studied multicellular fungal model Neurospora crassa. We characterized morphological development and genome-wide transcriptomics in the closely related species Neurospora crassa, Neurospora tetrasperma, and Neurospora discreta, across eight stages of sexual development. Despite diverse life histories within the genus, all three species produce vase-shaped perithecia. Transcriptome sequencing provided gene expression levels of orthologous genes among all three species. Expression of key meiosis genes and sporulation genes corresponded to known phenotypic and developmental differences among these Neurospora species during sexual development. We assembled a list of genes putatively relevant to the recent evolution of fruiting body development by sorting genes whose relative expression across developmental stages increased more in N. crassa relative to the other species. Then, in N. crassa, we characterized the phenotypes of fruiting bodies arising from crosses of homozygous knockout strains of the top genes. Eight N. crassa genes were found to be critical for the successful formation of perithecia. The absence of these genes in these crosses resulted in either no perithecium formation or in arrested development at an early stage. Our results provide insight into the genetic basis of Neurospora sexual reproduction, which is also of great importance with regard to other multicellular ascomycetes, including perithecium-forming pathogens, such as Claviceps purpurea, Ophiostoma ulmi, and Glomerella graminicola.

Project description:Studies using yeast have advanced our understanding of both replicative and chronological aging, leading to the discovery of longevity genes that have homologues in higher eukaryotes. Chronological lifespan in yeast is conventionally defined as the lifespan of a non-dividing cell. To date, this parameter has only been estimated under calorically restricted (CR) conditions, mimicked by starvation. Since post-mitotic cells in higher eukaryotes are rarely calorically-restricted, we sought to develop an alternative experimental system where non-dividing yeast would age chronologically, in the presence of excess nutrients. We report here on a system wherein alginate-encapsulated yeast are packed in a pH- and temperature-controlled bioreactor, then continuously fed non-limiting substrate for extended periods of time. We present demographic, physiological and genomic evidence indicating that after ~120 hrs, immobilized cells cease dividing, remain metabolically very active and retain >95% viability for periods of 17 days. Over the same time interval, starved planktonic cells, cultured using the same media, and also controlled for temperature and pH, retained < 1 % viability in both aerobic and anaerobic cultures,. Unlike planktonic yeast, continuously-fed immobilized cells hyper-accumulate glycogen. FACS analysis of SYTOX green-stained yeast confirms that immobilized cells completely arrest within 5 days of culture, and unlike starving planktonic cells, remain free thereafter of replicative stress and are non-apoptotic. This unusual state is supported by a global gene expression profile that is stable over time, repeatable across replicate experiments, and altogether distinct from planktonic cells cultured in the presence and absence of limiting nutrients. DNA expression profiling, performed here for the very first time on immobilized cells, reveals that glycolytic genes and their trans-acting regulatory elements are upregulated, as are genes involved in remodeling the cell wall and resisting stress; by contrast, many genes that promote cell cycle progression and carry out oxidative metabolism are repressed. Stress resistance transcription factor MSN4 and its upstream effector RIM15 are conspicuously upregulated in the immobilized state, suggesting that nutrient-sensing pathways may play a role in cell viability and longevity when yeast are immobilized and placed in prolonged culture under calorically-unrestricted conditions. The cell cycle arrest in the immobilized state is mediated by RIM 15. Over the time-course of our experiments, well-fed, non-diving immobilized cells do not appear to age. Keywords: comparison of growth states and a time course of immobilized cells Nine growth conditions or time points with two to four replicates each

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Gene expression levels in three Neurospora species reveal genes crucial for sexual reproduction in Neurospora

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