Dokument: Genetic regulation of photoperiod-dependent flowering time in barley (Hordeum vulgare L.)
Titel: | Genetic regulation of photoperiod-dependent flowering time in barley (Hordeum vulgare L.) | |||||||
URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=65289 | |||||||
URN (NBN): | urn:nbn:de:hbz:061-20250416-084204-2 | |||||||
Kollektion: | Dissertationen | |||||||
Sprache: | Englisch | |||||||
Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
Medientyp: | Text | |||||||
Autor: | Helmsorig, Gesa [Autor] | |||||||
Dateien: |
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Beitragende: | Prof. Dr. von Korff Schmising, Maria [Gutachter] Prof. Dr. Rüdiger Simon [Gutachter] | |||||||
Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 580 Pflanzen (Botanik) | |||||||
Beschreibung: | Time to flower is critical for the successful propagation of a plant and to optimize crop yield. Several internal and external factors, including photoperiod, regulate flowering. Photoperiodic flowering is well-studied in model organisms such as Arabidopsis (Arabidopsis thaliana), and key flowering time regulators are conserved across angiosperm species. However, the functions of these floral regulators and molecular networks have diverged between angiosperm lineages and species. In the cereal crop barley (Hordeum vulgare L.), the central flowering time regulator in response to long photoperiods is PHOTOPERIOD 1 (Ppd-H1), ortholog of the pseudo-response regulator genes from the circadian clock in Arabidopsis. Ppd-H1 induces the expression of FLOWERING LOCUS T1 (FT1), the barley ortholog of Arabidopsis florigen FT, which in Arabidopsis moves from leaf to shoot apex to induce the formation of flowers. In contrast to Arabidopsis, the barley genome holds several FT-like genes, of which only some have been characterized so far, and the exact role of FT1 remains poorly understood. In this work, I aimed to identify and characterize an upstream regulator of Ppd-H1 and FT1 and detect downstream molecular and phenotypic effects in the developing shoot and inflorescence meristems. For this, I identified and functionally characterized the gene underlying the early maturity 7 (eam7) locus, which confers photoperiod-independent early flowering in barley. In addition, I dissected the function of FT1 in controlling reproductive timing, and shoot and inflorescence meristem development and linked this to molecular networks in the leaf, stem and inflorescence.
In the first part of this dissertation, I identified the gene underlying the eam7 locus. Barley is a facultative long-day plant; photoperiods above 12 hours strongly induce flowering, whereas those below 12 hours of light delay flowering. Plants carrying the eam7 locus are early flowering under non-inductive short-day conditions. Phenotypic characterization of eam7 plants showed that eam7 interacts with Ppd-H1 to regulate photoperiodic flowering, inflorescence development, and plant fertility. I generated a biparental mapping population segregating for Ppd-H1 and eam7 to map the position of the eam7 locus on the short arm of chromosome 6H. Target gene sequencing revealed a 34 base pair deletion in the coding sequence of LIGHT-REGULATED WD 1 (LWD1), homologous to a gene involved in the light entrainment of the circadian clock in Arabidopsis, to co-segregate with the early flowering phenotype of eam7 under short days. With CRISPR-Cas9, I generated lwd1 mutants to confirm the early flowering phenotype of homozygous mutants under short-day conditions. Subsequent complementation crosses confirmed LWD1 as a promising candidate gene to underlie eam7. Gene expression studies showed that changes in the LWD1 coding sequence caused the de-repression of Ppd-H1 at night and consequent upregulation of FT1 under short days. Furthermore, mutations in lwd1 caused altered diurnal expression patterns of phytochromes and clock genes, indicating that LWD1 controls the photoperiod response by modifying the light entrainment of the clock and clock gene expression. In the second part of this thesis, I characterized FLOWERING LOCUS T1 (FT1), which is one of several FT-like genes in barley. FT1 is suggested to be the central inducer of flowering in barley as allelic variation at Ppd-H1 correlates with altered FT1 expression levels and consequent timing of flowering under long days. I aimed to understand how and to what extent FT1 affects flowering, plant development, and architecture, whether the photoperiodic response conveyed by Ppd-H1 is transmitted exclusively through FT1, and to identify gene regulatory networks downstream of FT1. Phenotyping CRISPR-Cas9-generated ft1 knock-out mutants revealed that FT1 strongly promotes flowering in barley but is not essential for the formation and development of inflorescences. Allelic variation at Ppd-H1 did not affect flowering time in ft1 mutants, indicating that Ppd-H1 regulates reproductive development exclusively via FT1. The ft1 mutant plants were characterized by a strong delay in the transition from vegetative to reproductive development and in the subsequent floral development, and tillered and flowered over many months. These results showed that FT1 affects the timing, synchrony, and duration of flowering. Through the microscopic dissection of the main shoot apex, I could show that ft1 mutants are characterized by increased spikelet meristems induced on the inflorescence. However, floret fertility decreased, resulting in an overall strong reduction in grain number per spike. FT1 impacts the balance of vegetative to reproductive tissue, as ft1 plants produced more side shoots but significantly fewer grains than parental wild-type plants. I used transcriptomic analyses to decipher the genetic network regulated by FT1. This revealed that FT1 affects numerous developmental genes in the shoot apex, possibly causative for the observed changes in meristem determinacy and, consequently, differences in longevity and duration of flowering. In addition, the expression of photosynthesis components and elements of the carbohydrate metabolism were altered, indicating that source-sink relationships are regulated through FT1. The expression patterns of genes involved in stress response were upregulated in the leaf and shoot apex possibly due to an imbalance of source-sink relationships in the ft1 mutants. In summary, I identified a novel regulator of photoperiodic flowering in barley, LWD1, and provided new insights into the role of FT1 in the complex network of flowering time regulation. This expands our knowledge of the molecular and genetic regulation of flowering time and can help us adapt our crops to increasingly challenging environmental conditions. | |||||||
Lizenz: | ![]() Dieses Werk ist lizenziert unter einer Creative Commons Namensnennung 4.0 International Lizenz | |||||||
Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät | |||||||
Dokument erstellt am: | 16.04.2025 | |||||||
Dateien geändert am: | 16.04.2025 | |||||||
Promotionsantrag am: | 29.11.2023 | |||||||
Datum der Promotion: | 07.02.2024 |