Molecular markers to characterize the hermaphroditic reproductive system of the planarian Schmidtea mediterranea
ABSTRACT: Investigation of differences in gene expression between two strains of the planarian Schmidtea mediterranea. The sexual strain are cross-fertilizing hermaphrodites with reproductive organs that develop post-embryonically and the asexual strain reproduces exclusively by transverse fission and fail to develop reproductive organs. A two chip study using total RNA recovered from asexual and sexual animals. Each chip measures the expression level of 16,797 ESTs from S. mediterranea with 10 60-mer probe pairs (PM/MM) per gene, with two-fold technical redundancy.
Project description:Investigation of whole genome gene expression level changes in nanos(RNAi) Schmidtea mediterranea, compared to control animals. nanos(RNAi) animals are devoid of germ cells The samples analyzed in this study are further described in Wang, Y., Stary, JM., Wilhelm, JE. and Newmark, PA. 2010. A eight chip study using total RNA recovered from asexual nanos(RNAi), asexual control, juvenile sexual nanos(RNAi), and juvenile sexual control animals. Each chip measures the expression level of 16,797 ESTs from S. mediterranea with 10 60-mer probe pairs (PM/MM) per gene, with two-fold technical redundancy.
Project description:The freshwater planarian Schmidtea mediterranea exhibits two distinct reproductive modes. Individuals of the sexual strain are cross-fertilizing hermaphrodites with reproductive organs that develop post-embryonically. By contrast, individuals of the asexual strain reproduce exclusively by transverse fission and fail to develop reproductive organs. These different reproductive strains are associated with distinct karyotypes, making S. mediterranea a useful model for studying germline development and sexual differentiation.To identify genes expressed differentially between these strains, we performed microarray analyses and identified >800 genes that were upregulated in the sexual planarian. From these, we characterized 24 genes by fluorescent in situ hybridization (FISH), revealing their expression in male germ cells or accessory reproductive organs. To identify additional markers of the planarian reproductive system, we also used immuno- and fluorescent lectin staining, identifying several antibodies and lectins that labeled structures associated with reproductive organs.Collectively, these cell-type specific markers will enable future efforts to characterize genes that are important for reproductive development in the planarian.
Project description:The transcriptome of the planarian Schmidtea mediterranea is not well characterized. We have used RNA-Seq to characterize the transcriptome in both sexual and asexual strains of S. mediterranea from both untreated and irradiated animals. Moreover, we have performed RNA-Seq on RNA purified from FACS sorted neoblasts and differentiated cells. Together these studies expand our understanding of the planarian transcriptome and have identified strain-specific, neoblast-specific, and conserved transcripts. RNA-Seq was performed on RNA isolated from untreated and irradiated S. mediterranea animals from both the sexual and asexual strains, on FACS purified X1 neoblasts, X2 neoblasts, and Xins differentiated cells. One of the raw data files for GSM847465 is missing. The fasta file is provided at http://genome.vcell.uchc.edu/GenomeData02/Graveley_Lab_Public_Data/Planarian/S.mediterranea_SexNIRmRNA3.fa.gz
Project description:Sexual reproduction is essential for the life cycle of most angiosperms. However, pseudovivipary is an important reproductive strategy in some grasses. In this mode of reproduction, asexual propagules are produced in place of sexual reproductive structures. However, the molecular mechanism of pseudovivipary still remains a mystery. In this work, we found three naturally occurring mutants in rice, namely, phoenix (pho), degenerative palea (dep), and abnormal floral organs (afo). Genetic analysis of them indicated that the stable pseudovivipary mutant pho was a double mutant containing both a Mendelian mutation in DEP and a non-Mendelian mutation in AFO. Further map-based cloning and microarray analysis revealed that dep mutant was caused by a genetic alteration in OsMADS15 while afo was caused by an epigenetic mutation in OsMADS1. Thus, OsMADS1 and OsMADS15 are both required to ensure sexual reproduction in rice and mutations of them lead to the switch of reproductive habit from sexual to asexual in rice. For the first time, our results reveal two regulators for sexual and asexual reproduction modes in flowering plants. In addition, our findings also make it possible to manipulate the reproductive strategy of plants, at least in rice.
Project description:BACKGROUND: Schmidtea mediterranea (Platyhelminthes, Tricladida, Continenticola) is found in scattered localities on a few islands and in coastal areas of the western Mediterranean. Although S. mediterranea is the object of many regeneration studies, little is known about its evolutionary history. Its present distribution has been proposed to stem from the fragmentation and migration of the Corsica-Sardinia microplate during the formation of the western Mediterranean basin, which implies an ancient origin for the species. To test this hypothesis, we obtained a large number of samples from across its distribution area. Using known and new molecular markers and, for the first time in planarians, a molecular clock, we analysed the genetic variability and demographic parameters within the species and between its sexual and asexual populations to estimate when they diverged. RESULTS: A total of 2 kb from three markers (COI, CYB and a nuclear intron N13) was amplified from ~200 specimens. Molecular data clustered the studied populations into three groups that correspond to the west, central and southeastern geographical locations of the current distribution of S. mediterranea. Mitochondrial genes show low haplotype and nucleotide diversity within populations but demonstrate higher values when all individuals are considered. The nuclear marker shows higher values of genetic diversity than the mitochondrial genes at the population level, but asexual populations present lower variability than the sexual ones. Neutrality tests are significant for some populations. Phylogenetic and dating analyses show the three groups to be monophyletic, with the west group being the basal group. The time when the diversification of the species occurred is between ~20 and ~4 mya, although the asexual nature of the western populations could have affected the dating analyses. CONCLUSIONS: S. mediterranea is an old species that is sparsely distributed in a harsh habitat, which is probably the consequence of the migration of the Corsica-Sardinia block. This species probably adapted to temperate climates in the middle of a changing Mediterranean climate that eventually became dry and hot. These data also suggest that in the mainland localities of Europe and Africa, sexual individuals of S. mediterranea are being replaced by asexual individuals that are either conspecific or are from other species that are better adapted to the Mediterranean climate.
Project description:Investigation of whole genome gene expression level changes in nanos(RNAi) Schmidtea mediterranea, compared to control animals. nanos(RNAi) animals are devoid of germ cells The samples analyzed in this study are further described in Wang, Y., Stary, JM., Wilhelm, JE. and Newmark, PA. 2010. Overall design: A eight chip study using total RNA recovered from asexual nanos(RNAi), asexual control, juvenile sexual nanos(RNAi), and juvenile sexual control animals. Each chip measures the expression level of 16,797 ESTs from S. mediterranea with 10 60-mer probe pairs (PM/MM) per gene, with two-fold technical redundancy.
Project description:A major goal of molecular evolutionary biology is to understand the fate and consequences of duplicated genes. In this context, aphids are particularly intriguing because the newly sequenced pea aphid genome is characterized by extraordinarily high levels of lineage-specific gene duplication relative to other insect genomes. While analyzing the results of a microarray comparing gene expression between male, sexual female and asexual female Myzus persicae aphids, we unexpectedly found duplicated nutrient amino acid transporters highly upregulated in males. These transporters, homologous to the Drosophila slimfast, belong to an aphid-specific gene family expansion in which other paralogs are thought to have functionally diverged to fill a role in mediating interactions between aphids and their nutrititonally required bacterial symbiont. The lack of a known male role for slimfast in other insects suggests that aphid slimfast paralogs have been retained as a result of functional divergence to fill multiple novel functional roles in symbiosis and in males. Two biological replicates, four treatments (males, asexual females at long day, asexual females at short day, sexual females), dye flip
Project description:Freshwater planarians have prodigious regenerative abilities that enable them to form complete organisms from tiny body fragments. This plasticity is also exhibited by the planarian germ cell lineage. Unlike many model organisms in which germ cells are specified by localized determinants, planarian germ cells appear to be specified epigenetically, arising postembryonically from stem cells. The planarian Schmidtea mediterranea is well suited for investigating the mechanisms underlying epigenetic germ cell specification. Two strains of S. mediterranea exist: a hermaphroditic strain that reproduces sexually and an asexual strain that reproduces by means of transverse fission. To date, expressed sequence tags (ESTs) have been generated only from the asexual strain. To develop molecular reagents for studying epigenetic germ cell specification, we have sequenced 27,161 ESTs from two developmental stages of the hermaphroditic strain of S. mediterranea; this collection of ESTs represents approximately 10,000 unique transcripts. blast analysis of the assembled ESTs showed that 66% share similarity to sequences in public databases. We annotated the assembled ESTs using Gene Ontology terms as well as conserved protein domains and organized them in a relational database. To validate experimentally the Gene Ontology annotations, we used whole-mount in situ hybridization to examine the expression patterns of transcripts assigned to the biological process "reproduction." Of the 53 genes in this category, 87% were expressed in the reproductive organs. In addition to its utility for studying germ cell development, this EST collection will be an important resource for annotating the planarian genome and studying this animal's amazing regenerative abilities.
Project description:Cytoplasmic polyadenylation is a mechanism of mRNA regulation prevalent in metazoan germ cells; it is largely dependent on Cytoplasmic Polyadenylation Element Binding proteins (CPEBs). Two CPEB homologs were identified in the planarian Schmidtea mediterranea. Smed-CPEB1 is expressed in ovaries and yolk glands of sexually mature planarians, and required for oocyte and yolk gland development. In contrast, Smed-CPEB2 is expressed in the testes and the central nervous system; its function is required for spermatogenesis as well as non-autonomously for development of ovaries and accessory reproductive organs. Transcriptome analysis of CPEB knockdown animals uncovered a comprehensive collection of molecular markers for reproductive structures in S. mediterranea, including ovaries, testes, yolk glands, and the copulatory apparatus. Analysis by RNA interference revealed contributions for a dozen of these genes during oogenesis, spermatogenesis, or capsule formation. We also present evidence suggesting that Smed-CPEB2 promotes translation of Neuropeptide Y-8, a prohormone required for planarian sexual maturation. These findings provide mechanistic insight into potentially conserved processes of germ cell development, as well as events involved in capsule deposition by flatworms.
Project description:Sexual Schmidtea mediterranea Trunk Regeneration. Sexual biotype Schmidtea mediterranea trunk fragments were sequenced at 0 day, 3 day, 5 day and 7 day post amputation along with whole worm juvenile animals in order identify sexual specific transcripts. Juvenile worms lack sex organs, testes and ovaries present in D0 trunk fragments. Days 3-7 represent time points of degeneration and regeneration of the sexual organs, testes and ovaries. Overall design: Day 0 trunk fragments, Day3, Day 5 and Day 7 regenerations and intact juvenile animals