Project description:We isolated pre-meiotic and early meiotic cells from 24 maize anthers, covering a week of development from the day after archesporial (AR) cell specification to the early zygotene stage of meiotic prophase I. Starting material was staged by anther length, and anther stages were densely sampled from throughout this period. High quality reads were obtained from 144 cells.
Project description:Ray2013 - S.cerevisiae meiosis-specific metabolic network
Meiosis is a strongly concerved cell division program that generates haploid gametes from a diploid parental cell. Successful meiosis is the fundamental basis of sexual reproduction. Multiple lines of evidence suggest a tight link between meiosis and metabolism. Here, yeast meiosis is studied to elucidate the link between reproduction and metabolism. Network flux is obtained using GLPK (GNU Linear Programming Kit) supported by the COBRA Toolbox for Matlab.
This model is described in the article:
Characterization of the metabolic requirements in yeast meiosis.
Ray D, Ye P.
PLoS One. 2013 May 8;8(5):e63707.
Abstract:
The diploid yeast Saccharomyces cerevisiae undergoes mitosis in glucose-rich medium but enters meiosis in acetate sporulation medium. The transition from mitosis to meiosis involves a remarkable adaptation of the metabolic machinery to the changing environment to meet new energy and biosynthesis requirements. Biochemical studies indicate that five metabolic pathways are active at different stages of sporulation: glutamate formation, tricarboxylic acid cycle, glyoxylate cycle, gluconeogenesis, and glycogenolysis. A dynamic synthesis of macromolecules, including nucleotides, amino acids, and lipids, is also observed. However, the metabolic requirements of sporulating cells are poorly understood. In this study, we apply flux balance analyses to uncover optimal principles driving the operation of metabolic networks over the entire period of sporulation. A meiosis-specific metabolic network is constructed, and flux distribution is simulated using ten objective functions combined with time-course expression-based reaction constraints. By systematically evaluating the correlation between computational and experimental fluxes on pathways and macromolecule syntheses, the metabolic requirements of cells are determined: sporulation requires maximization of ATP production and macromolecule syntheses in the early phase followed by maximization of carbohydrate breakdown and minimization of ATP production in the middle and late stages. Our computational models are validated by in silico deletion of enzymes known to be essential for sporulation. Finally, the models are used to predict novel metabolic genes required for sporulation. This study indicates that yeast cells have distinct metabolic requirements at different phases of meiosis, which may reflect regulation that realizes the optimal outcome of sporulation. Our meiosis-specific network models provide a framework for an in-depth understanding of the roles of enzymes and reactions, and may open new avenues for engineering metabolic pathways to improve sporulation efficiency.
This model is hosted on BioModels Database
and identified
by: MODEL1303140001
.
To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource
for published quantitative kinetic models
.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to the public
domain worldwide. Please refer to CC0 Public Domain
Dedication
for more information.
Project description:Meiosis produces gametes through a specialised, two-step cell division, which is highly error-prone in humans. Reductional meiosis I, where maternal and paternal chromosomes (homologs) segregate, is followed by equational meiosis II, where sister chromatids separate. Uniquely during meiosis I, sister kinetochores are monooriented and pericentromeric cohesin is protected. Here, we demonstrate that these key adaptations for reductional chromosome segregation are achieved through separable control of multiple kinases by the meiosis I-specific budding yeast Spo13 protein. Recruitment of Polo kinase to kinetochores directs monoorientation, while, independently, cohesin protection is achieved by controlling the effects of cohesin kinases. Therefore, reductional chromosome segregation, the defining feature of meiosis, is established by multifaceted kinase control by a master regulator. The recent identification of Spo13 orthologs, fission yeast Moa1 and mouse MEIKIN, suggests that kinase coordination by a master meiosis I regulator may be a general feature in the establishment of reductional chromosome segregation.
Project description:Genome haploidization at meiosis depends on two consecutive nuclear divisions, which are controlled by an oscillatory system consisting of Cdk1-cyclin B and the APC/C bound to the Cdc20 activator. How the oscillator generates exactly two divisions has been unclear. We have studied this question in yeast where exit from meiosis involves accumulation of the APC/C activator Ama1 at meiosis II. We show that inactivation of the meiosis I-specific protein Spo13/MEIKIN results in a single-division meiosis due to premature activation of APC/CAma1. In the wild-type, Spo13 bound to the polo-like kinase Cdc5 prevents Ama1 synthesis at meiosis I by stabilizing the translational repressor Rim4. In addition, Cdc5-Spo13 inhibits the activity of Ama1 by converting the B-type cyclin Clb1 from a substrate to an inhibitor of Ama1. Cdc20-dependent degradation of Spo13 at anaphase I unleashes a feedback loop that increases Ama1’s synthesis and activity, leading to irreversible exit from meiosis at the second division. Thus, by repressing the exit machinery at meiosis I, Cdc5-Spo13 ensures that cells undergo two divisions to produce haploid gametes.
Project description:Plants do not specify their germline until late in their life cycle. Hence, the plant germline is normally specified from terminally differentiated somatic cells, though the precise mechanism(s) are unknown. We have found that male gametogenesis in maize is associated with the accumulation of distinct 21-nt phased small-interfering RNAs (phasiRNAs) generated by meiosis-associated argonaute (MAGO) proteins. MAGO1 accumulates in the epidermis of pre-meiotic anthers while MAGO2 is found in developing meiocytes. We have found that MAGO proteins are required for meiocyte development as mutants display chromosomal defects and male infertility. Furthermore, we detect the heat stress-induced activation of a distinct class of Long terminal repeat retrotransposons in the male germline of MAGO mutants. Our data suggests that MAGO proteins and the reproductive phasiRNAs play important roles protecting the germline from transposable elements during environmental stress conditions.
Project description:Meiosis is a specialized cell division that generates gametes, such as eggs and sperm. Errors in meiosis result in miscarriages and are the leading cause of birth defects, however the molecular origins of these defects remain unknown. Studies in model organisms are beginning to identify the genes and pathways important for meiosis, but the parts list is still poorly defined. Here we present a comprehensive catalogue of genes required for meiosis in the fission yeast, Schizosaccharomyces pombe. Our genome-wide functional screen surveyed all non-essential genes for roles in chromosome segregation and spore formation. Novel genes required at distinct stages of the meiotic chromosome segregation and differentiation programme were identified. Preliminary characterization implicated three of these genes in centrosome/spindle pole body function, centromere and cohesion function. Our findings represent a near-complete parts list of genes required for meiosis in fission yeast, providing a valuable resource to advance our molecular understanding of meiosis.
Project description:In the human fungal pathogen Cryptococcus neoformans, sexual mating is considered to benefit its infections through meiosis-driven hyper-virulent variants and infectious meiotic spores. How meiotic cycle and mating differentiation program are genetically and developmentally integrated to safeguard successful meiotic sporulation remains poorly known. In C. neoformans, sporulation occurs following two parallel events, meiosis and differentiation of specialized cell termed basidium. To reveal the gene circuits specifically orchestrating basidial maturation and meiosis, we performed high-coverage stand-specific RNA-sequencing analysis to monitor gene induction timing through unisexual differentiation and reveals a co-regulation of these two events by a shared regulatory program. Our findings indicated that the regulatory coupling of meiosis and basidial development may serve as a determinant underlying production of infectious meiospores in C. neoformans.
Project description:N6-methyladenosine (m6A) is the most ubiquitous mRNA base modification, but little is known about its precise location, temporal dynamics, and regulation. Here, we generated genomic maps of m6A sites in meiotic yeast transcripts at nearly single-nucleotide resolution, identifying 1,308 putatively methylated sites within 1,183 transcripts. We validated 8/8 methylation sites in different genes with direct genetic analysis, demonstrated that methylated sites are significantly conserved in a related species, and built a model that predicts methylated sites directly from sequence. Sites vary in their methylation profiles along a dense meiotic time-course, and are regulated both locally, via predictable methylatability of each site, and globally, through the core meiotic circuitry. The methyltransferase complex components localize to the yeast nucleolus, and this localization is essential for mRNA methylation. Our data illuminates a conserved, dynamically regulated methylation program in yeast meiosis, and provides an important resource for studying the function of this epitranscriptomic modification.
Project description:Starvation in diploid budding yeast cells triggers a cell-fate program culminating in meiosis and spore formation. Transcription activation of early meiotic genes (EMGs) hinges on the transcription activator Ime1, its DNA-binding partner Ume6, and GSK-3 kinase Rim11. Phosphorylation of Ume6 by Rim11 is key for EMG activation. We report that Rim11 functions as the central signal integrator for controlling Ume6 phosphorylation and EMG transcription. In nutrient-rich conditions, PKA suppresses Rim11 levels, while TORC1 retains Rim11 in the cytoplasm. Inhibiting PKA and TORC1 induces Rim11 expression and nuclear localization. Remarkably, nuclear Rim11 is required, but not sufficient, for Rim11-dependent Ume6 phosphorylation. Additionally, Ime1 is an essential anchor protein for phosphorylating Ume6. Subsequently, Ume6-Ime1 coactivator complexes form, which drive EMG transcription. Our results demonstrate how varied signalling inputs (PKA/TORC1/Ime1) converge through Rim11 to regulate EMG expression and meiosis initiation. We posit that the signalling-regulatory network elucidated here generates robustness in cell-fate control.