Cell Biology & Molecular Genetics

Permanent URI for this communityhttp://hdl.handle.net/1903/11811

Browse

Subject: search.filters.subject.Strawberry

Search Results

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Genome-wide identification and analysis of imprinted genes in strawberry seed development
    (2022) Joldersma, Dirk; Liu, Zhongchi Anne; Taneyhill, Lisa Anne; Cell Biology & Molecular Genetics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The activation of zygotic gene expression is of fundamental importance to reproductive biology, but its regulation remains poorly understood. Within Angiosperm plants, fertilization occurs simultaneously in two locations, the embryo and its genetic twin, the endosperm, a nutritive tissue that is a defining feature of Angiosperm reproduction. Auxin hormone synthesized in the endosperm is essential to seed and fruit development. In the diploid strawberry Fragaria vesca, that auxin synthesis is regulated by FveAGL62, which is expressed specifically after fertilization in endosperm. How fertilization activates FveAGL62 expression in the endosperm, however, is presently unknown. I investigated the hypothesis that epigenetically regulated maternally- and paternally expressed genes (MEGs and PEGs, and together, “imprinted genes”) regulate the expression of FveAGL62. I hybridized two F. vesca accessions, isolated the endosperm from the F1 seeds, and sequenced the transcriptome of the F1 endosperm—a result facilitated by strawberry’s uniquely accessible seed. To identify imprinted genes within the endosperm, I assembled and annotated the genome of the maternal parent, F. vesca accession “Yellow Wonder” (FvYW5AF7), a model for the commercial strawberry. The paternal parent genome was obtained from a collaborator. 809 PEGs and 825 MEGs were identified from RNA sequencing reads that align uniquely to the maternal or paternal genome. MEGs are enriched in genes catabolizing auxin and hence limit seed growth, while PEGs are enriched in genes involved in histone modification, thereby promoting cell differentiation and seed growth. The distinct roles of MEGs and PEGs supports and can be explained by parental conflict and kinship theories, which predict a maternal genome tends to restrict progeny consumption of maternal resources, while a paternal genome will encourage such consumption. In contrast to findings in other species, I find that the endosperm-specific auxin biosynthetic gene FveYUC10 is maternally expressed, but while its imprinting status has changed, it may still function as a fertilization sensor. The maternally expressed gene FveMYB98 contains a binding domain that targets motifs present in FveAGL62’s promoter and its homolog binds AtAGL62 promoter in Arabidopsis. With collaborators, I showed that overexpression and CRISPR knockout of FveMYB98 changes seed size. Transient expression, yeast one hybrid and quantitative PCR analyses suggest that FveMYB98 represses FveYUC10 expression directly and FveAGL62 expression indirectly. These results suggest that FveMYB98 expression is a vehicle for maternal regulation of the level of auxin in the endosperm and thereby endosperm proliferation and seed size. My dissertation research has produced a new genome assembly of a model strawberry, a transcriptome of strawberry endosperm, and identified imprinted genes at genomic scale. I find FveMYB98 regulates seed size—a function echoed broadly within MEG and PEG classes—providing supporting evidence for the parental conflict theory within the developing progeny. These results improve our understanding of zygotic expression in developing seeds, addressing a fundamental scientific gap and, more tangibly, may enable future production of fertilization-independent seeds and seedless fruits. 
  • Thumbnail Image
    Item
    SGR: an online genomic resource for the woodland strawberry
    (Springer Nature, 2013-12-23) Darwish, Omar; Slovin, Janet P; Kang, Chunying; Hollender, Courtney A; Geretz, Aviva; Houston, Sam; Liu, Zhongchi; Alkharouf, Nadim W
    Fragaria vesca, a diploid strawberry species commonly known as the alpine or woodland strawberry, is a versatile experimental plant system and an emerging model for the Rosaceae family. An ancestral F. vesca genome contributed to the genome of the octoploid dessert strawberry (F. ×ananassa), and the extant genome exhibits synteny with other commercially important members of the Rosaceae family such as apple and peach. To provide a molecular description of floral organ and fruit development at the resolution of specific tissues and cell types, RNAs from flowers and early developmental stage fruit tissues of the inbred F. vesca line YW5AF7 were extracted and the resulting cDNA libraries sequenced using an Illumina HiSeq2000. To enable easy access as well as mining of this two-dimensional (stage and tissue) transcriptome dataset, a web-based database, the Strawberry Genomic Resource (SGR), was developed. SGR is a web accessible database that contains sample description, sample statistics, gene annotation, and gene expression analysis. This information can be accessed publicly from a web-based interface at http://bioinformatics.towson.edu/strawberry/Default.aspx . The SGR website provides user friendly search and browse capabilities for all the data stored in the database. Users are able to search for genes using a gene ID or description or obtain differentially expressed genes by entering different comparison parameters. Search results can be downloaded in a tabular format compatible with Microsoft excel application. Aligned reads to individual genes and exon/intron structures are displayed using the genome browser, facilitating gene re-annotation by individual users. The SGR database was developed to facilitate dissemination and data mining of extensive floral and fruit transcriptome data in the woodland strawberry. It enables users to mine the data in different ways to study different pathways or biological processes during reproductive development.
  • Thumbnail Image
    Item
    Re-annotation of the woodland strawberry (Fragaria vesca) genome
    (Springer Nature, 2015-01-27) Darwis, Omar; Shahan, Rachel; Liu, Zhongchi; Slovin, Janet P; Alkharouf, Nadim W
    Fragaria vesca is a low-growing, small-fruited diploid strawberry species commonly called woodland strawberry. It is native to temperate regions of Eurasia and North America and while it produces edible fruits, it is most highly useful as an experimental perennial plant system that can serve as a model for the agriculturally important Rosaceae family. A draft of the F. vesca genome sequence was published in 2011 [Nat Genet 43:223,2011]. The first generation annotation (version 1.1) were developed using GeneMark-ES+[Nuc Acids Res 33:6494,2005]which is a self-training gene prediction tool that relies primarily on the combination of ab initio predictions with mapping high confidence ESTs in addition to mapping gene deserts from transposable elements. Based on over 25 different tissue transcriptomes, we have revised the F. vesca genome annotation, thereby providing several improvements over version 1.1. The new annotation, which was achieved using Maker, describes many more predicted protein coding genes compared to the GeneMark generated annotation that is currently hosted at the Genome Database for Rosaceae (http://www.rosaceae.org/). Our new annotation also results in an increase in the overall total coding length, and the number of coding regions found. The total number of gene predictions that do not overlap with the previous annotations is 2286, most of which were found to be homologous to other plant genes. We have experimentally verified one of the new gene model predictions to validate our results. Using the RNA-Seq transcriptome sequences from 25 diverse tissue types, the re-annotation pipeline improved existing annotations by increasing the annotation accuracy based on extensive transcriptome data. It uncovered new genes, added exons to current genes, and extended or merged exons. This complete genome re-annotation will significantly benefit functional genomic studies of the strawberry and other members of the Rosaceae.
  • Thumbnail Image
    Item
    Global identification and analysis of long non-coding RNAs in diploid strawberry Fragaria vesca during flower and fruit development
    (Springer Nature, 2015-10-19) Kang, Chunying; Liu, Zhongchi
    Long non-coding RNAs (lncRNAs) are a new class of regulatory molecules with roles in diverse biological processes. While much effort has been invested in the analysis of lncRNAs from established plant models Arabidopsis, maize, and rice, almost nothing is known about lncRNAs from fruit crops, including those in the Rosaceae family. Here, we present a genome-scale identification and characterization of lncRNAs from a diploid strawberry, Fragaria vesca, based on rich RNA-seq datasets from 35 different flower and fruit tissues. 5,884 Fve-lncRNAs derived from 3,862 loci were identified. These lncRNAs were carefully cataloged based on expression level and whether or not they contain repetitive sequences or generate small RNAs. About one fourth of them are termed high-confidence lncRNAs (hc-lncRNAs) because they are expressed at a level of FPKM higher than 2 and produce neither small RNAs nor contain repetitive sequence. To identify regulatory interactions between lncRNAs and their potential protein-coding (PC) gene targets, pairs of lncRNAs and PC genes with positively or negatively correlated expression trends were identified based on their expression; these pairs may be candidates of cis- or trans-acting lncRNAs and their targets. Finally, blast searches within plant species indicate that lncRNAs are not well conserved. Our study identifies a large number of tissue-specifically expressed lncRNAs in F. vesca, thereby highlighting their potential contributions to strawberry flower and fruit development and paving the way for future functional studies.
  • Thumbnail Image
    Item
    A Network Approach to Identify Key Regulators of Fruit Development in Fragaria vesca, a Diploid Strawberry
    (2018) Shahan, Rachel; Liu, Zhongchi; Cell Biology & Molecular Genetics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Post-embryonic organogenesis is a feature unique to plants, an example of which is flower and fruit production. Previous work on strawberry fruit development has focused primarily on the latter stages, including ripening. Comparatively little is known about the molecular events underpinning fruit set, the pivotal stage at which fruit development proceeds or terminates. This thesis investigates early fruit development using Fragaria vesca, a diploid strawberry, as a model. In collaboration with a bioinformatician, I generated gene co-expression networks from 92 previously generated RNA-Seq libraries profiling multiple tissues and stages of strawberry flower and fruit development. I demonstrate the utility of co-expression networks in illuminating molecular processes underlying fruit development. Experimental validation of the networks includes demonstration of increased iron transport soon after fertilization and identification of FveUFO1 as an important regulator of floral meristem determinacy and floral organ identity. Using the co-expression networks, I discovered the surprising expression of FvFT1, a homolog of FLOWERING LOCUS T (FT), in the fleshy fruit immediately post-fertilization. In many plant species, the FT peptide is a non-cell autonomous signal that initiates flowering in response to inductive photoperiod. I found that FvFT1 expression is responsive to temperature, but not photoperiod, in strawberry fruit. Further, transcriptional activation is detectable in the vascular bundles connecting the fruit to the seeds, raising the possibility that FvFT1 may facilitate cross-tissue communication. Signal from an FvFT1-GFP translational fusion protein is visible in seed nuclei despite its localized transcription in the vasculature. However, analysis of FvFT1 RNAi plants failed to identify a fruit phenotype, possibly due to redundancy among three FvFT paralogs. Finally, to develop additional research tools for F. vesca, I isolated and tested fruit tissue-specific promoters based on genes identified with differential expression analyses. These analyses revealed genes strongly expressed in the receptacle fruit, thereby identifying potential regulators of early fruit development and attractive candidates for future study. Together, this work advances the systems-level infrastructure for studying molecular regulation of F. vesca fruit development, points to a novel role for FT distinct from its known function in floral initiation, and provides molecular tools useful to the F. vesca community.