Dokument: Studies into the Regulation of C4 Photosynthesis – Towards Factors Controlling Bundle Sheath Expression and Kranz Anatomy Development
| Titel: | Studies into the Regulation of C4 Photosynthesis – Towards Factors Controlling Bundle Sheath Expression and Kranz Anatomy Development | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=48208 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20190108-100317-1 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Dipl.-Biol. Emmerling, Jan [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Westhoff, Peter [Gutachter] Prof. Dr. Maria von Korff Schmising [Gutachter] | |||||||
| Stichwörter: | C4 Photosynthesis, Glycine Decarboxylase, Gene Regulation, Evolution, Kranz Anatomy, cis, trans | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 580 Pflanzen (Botanik) | |||||||
| Beschreibung: | Synthetic C4 photosynthesis could be the answer to ensure food security in face of
an exponentially growing world population. Thorough understanding of the molecular factors that control C4 photosynthesis is pivotal to its engineering. Since C4 photosynthesis requires precise spatial gene expression and a specialised leaf anatomy, this study strived to elucidate genetic factors that regulate these traits. Upstream flanking sequences of the GLDT gene from C3, C3-C4 and C4 Flaveria species were fused to reporter genes and analysed in C3 and C4 background. The results revealed that GLDT is differentially localised in C3 and C4 Flaveria species. It was shown that the underlying regulatory mechanism is also functional in distantly related C3 species and acts on transcriptional level. Sequence analysis indicated that spatially confined expression correlated with the presence of large conserved regions upstream of the GLDT gene. The insertions are exclusive to the only Flaveria clade that contains fully evolved C4 species. Deletion and substitution of these conserved regions showed that one of these regions is necessary for spatially confined expression. Consensus reconstruction from RNA-seq data suggested that this region corresponds to an ancient insertion of a small transposable element – a MITE – which seemed to be highly abundant in Flaveria species. Subsequent dissection narrowed down the region of interest to 59 bp. Additional swapping of conserved regions confirmed the presence of a second cis-regulatory element and sequence analysis identified 11 polymorphisms, which associate with differential expression of GLDT. In a similar approach, the upstream flanking sequence of a PCK gene from the C4 grass Zoysia japonica was isolated and analysed in the C3 background of rice. Reporter gene localisation showed expression exclusively in bundle sheath cells. Subsequent truncation and fusion constructs revealed that deletion of a 300 bp fragment altered the expression pattern from bundle sheath to mesophyll specific. Prediction of CREs indicated that only three known binding sites were exclusive to this region. Two of these corresponded to GOLDEN 2-like transcription factors (TFs) – known regulators of C4 photosynthesis and morphology. A comprehensive study previously identified 18 candidate-TFs that negatively correlated with development of C4 leaf anatomy. Here, orthologues of these negative regulator candidates were knocked down in rice, by hairpin-RNA-induced posttranscriptional gene silencing. The knock down was confirmed by quantitative real time PCR. Its impact on leaf anatomy was quantitatively assessed by measurement of three to four relevant anatomical parameters in the T0 generation. Although, some candidates induced strong phenotypes, none of the relevant parameters were severely affected. Similar was observed in a corresponding study, where 60 potential positive regulators were ectopically expressed in rice, but were unable to affect relevant parameters. These results indicated that either the early leaf developmental program is highly buffered against changes on transcriptional level or that the ZmUbi1 promoter – used by default in monocot species and utilised in both studies – is not as ubiquitously expressed as generally assumed. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie » Entwicklungs- und Molekularbiologie der Pflanzen | |||||||
| Dokument erstellt am: | 08.01.2019 | |||||||
| Dateien geändert am: | 08.01.2019 | |||||||
| Promotionsantrag am: | 24.09.2018 | |||||||
| Datum der Promotion: | 17.12.2018 |
