Dokument: Genetic Control of Shoot Architecture in Barley (Hordeum vulgare L.)
| Titel: | Genetic Control of Shoot Architecture in Barley (Hordeum vulgare L.) | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=52247 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20200218-102651-6 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Dr. Walla, Agatha Alexandra [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. von Korff, Maria [Gutachter] Prof. Dr. Rüdiger Simon [Gutachter] | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 580 Pflanzen (Botanik) | |||||||
| Beschreibung: | Shoot architecture is a major determinant of grain yield and a primary target for crop improvement. The activity of the shoot apical meristem and the axillary meristems determine branching (tillering) patterns, leaf number and inflorescence morphology. However, the genetic mechanisms underlying shoot architecture are not well characterized in the agronomically important cereal crop barley. This work reports about the identification of two important regulators of shoot architecture in barley, SIX-ROWED SPIKE3 (VRS3) and MANY NODED DWARF1 (MND1).
In the first part of this study, I investigated the genetic regulation of lateral spikelet development in the barley row-type mutant six-rowed spike3 (vrs3). The mutant spike is characterized by fertile lateral spikelets resulting in an increased number of seeds per spike when compared to the two-rowed wild-type. I established a mapping by sequencing approach based on RNA sequencing of allelic mutants to identify the causative mutation at the vrs3 locus. The comparison of sequence variations in two allelic backcross-derived vrs3 mutants and the backcross recipient cultivar uncovered the size, number and position of the introgressions and revealed only one candidate gene for the vrs3 locus in both mutant lines. The candidate gene encodes for a putative histone demethylase with a conserved zinc finger and Jumonji C and N domain. Resequencing of the candidate gene in 19 additional allelic mutant lines revealed a series of mutations in the conserved domains of the protein and thus confirmed the candidate. Analysis of differential gene expression in developing shoot apices suggested that VRS3 is a transcriptional activator of the known row-type genes VRS1 and INTERMEDIUM-C (INT-C). Furthermore, comparative transcriptome and qPCR analyses of the row-type mutants vrs3, vrs4 and int-c showed that the development of lateral spikelets was mediated by quantitative variation in VRS1 expression levels. Consequently, this work advanced our understanding of the genetic network controlling lateral spikelet development and row-type in barley. In the second part of this study, I characterized the barley high-tillering mutant many noded dwarf1 (mnd1) and identified the causal gene based on RNA sequencing and verification of the candidate gene in allelic mutant lines. Through detailed macro-and microscopic phenotyping, I could show that MND1 acts as an important repressor of vegetative growth and is thus critical in coordinating the reproductive phase transition. The mnd1 mutant is characterized by a prolonged phase of vegetative growth and a shortened phyllochron, resulting in an increased number of leaves and consequently tiller number. In addition, the mutant line formed aerial tillers at elongated nodes along the stem and at the inflorescence base. Scanning electron microscope images of mnd1 mutant inflorescences showed an insufficient bract suppression at basal rachis nodes coinciding with the reversion of floral meristems to branch meristems. On a molecular level, MND1 transcripts localized to axillary meristems in axils of young leaves and the vasculature of the shoot apical meristem (SAM) during the phase transition from vegetative to reproductive growth. Transcriptional profiling of developing inflorescences at three early reproductive stages revealed consistent expression changes of transcripts involved in cell cycle regulation, development and defense across all stages. Known modulators of phase change, such as LEAFY and TERMINAL FLOWER1 homologs, as well as floral homeotic transcription factors were deregulated in the mutant plants. Phylogenetic analysis revealed that MND1 is a close homolog of a putative rice histone H4 acetyltransferase. Future studies are required to investigate the functional conservation between MND1 and its closest rice homolog, as well as identification of direct downstream targets to reveal the underlying pathway of shoot branching control. Taken together, I identified two putative epigenetic modifiers, VRS3 and MND1, that control transcription in the shoot apex and thereby have strong pleiotropic effects on the barley shoot and inflorescence architecture. Whereas VRS3 is modulating expression levels of known row-type regulators, MND1 is changing expression domains of genes acting in the cell-cycle machinery and modifies expression levels of transcription factors which coordinate phase transition and enhance reproductive growth. My work provides new insights into the genetic and molecular regulation of shoot and spike architecture in barley which are important traits for yield improvement in cereals. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie » Genetik | |||||||
| Dokument erstellt am: | 18.02.2020 | |||||||
| Dateien geändert am: | 18.02.2020 | |||||||
| Promotionsantrag am: | 12.12.2018 | |||||||
| Datum der Promotion: | 25.02.2019 |
