Dokument: Characterization of mesophyll-specific promoters for C₄ engineering of rice and mutational analysis of leaf anatomy in Arabidopsis thaliana

Titel:	Characterization of mesophyll-specific promoters for C₄ engineering of rice and mutational analysis of leaf anatomy in Arabidopsis thaliana
URL für Lesezeichen:	https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=48188
URN (NBN):	urn:nbn:de:hbz:061-20190107-104319-2
Kollektion:	Dissertationen
Sprache:	Englisch
Dokumententyp:	Wissenschaftliche Abschlussarbeiten » Dissertation
Medientyp:	Text
Autor:	M.Sc Gupta, Shipan Das [Autor]
Dateien:	[Dateien anzeigen] Adobe PDF [Details] 5,29 MB in einer Datei [ZIP-Datei erzeugen] Dateien vom 07.01.2019 / geändert 07.01.2019
Beitragende:	Prof. Dr. Westhoff, Peter [Gutachter] Prof. Dr. Korff Schmising, Maria von [Gutachter]
Dewey Dezimal-Klassifikation:	500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie
Beschreibung:	C4 photosynthesis is a special kind of adaptation that alleviates the detrimental effects of photorespiration and has risen independently over 60 times from their C3 ancestors. Reduction in the photorespiration reaction in C4 photosynthetic plants is achieved through the metabolic cooperation of the mesophyll (M) and the bundle sheath (BS) cells. Crop plants that use the C4 photosynthetic cycle are more productive and use less water and nitrogen in relation with their C3 counterparts. These advantages of C4 photosynthesis, along with the demand for future crop security, have spurred the development of a program to install C4 traits into the C3 plant rice in order to increase the latter’s agricultural productivity. To achieve this goal, genes controlling the C4 leaf anatomy and the core C4 biochemical process need to be transferred to rice and expressed appropriately. Therefore, sets of cell-specific promoter units that can be used alternatively for the development of C4 rice are essential. In the first part of this thesis, the 5´-flanking sequences of the C4 phosphoenolpyruvate carboxylase (C4Ppc) gene from the Panicoid C4 grass species Setaria viridis, Panicum miliaceum and Urochloa maxima have been shown to direct mesophyll cell-specific expression of a reporter gene in rice leaf tissue. 5´-deletion analysis of these flanking sequences revealed that all the essential regulatory elements responsible for directing M cell-specific expression are located within their proximal 500 bp upstream of the translational start codon ATG. Comparative sequence analysis of the C4Ppc 5´-flanking sequences of six-selected C4 grass species identified four motifs of conserved nucleotide sequences (CNS) within this proximal 500 bp. Detailed promoter deletion and recombination analysis in rice revealed that the CNSs are essential for the activity of the C4Ppc promoter. Further investigation provided enough evidence that a putative interaction between the CNSs and an unknown upstream redundant element(s) directs the M cell-specific expression of the C4Ppc gene in many C4 grass species. One of the major obstacles for developing the C4 rice is the absence of C4-like leaf anatomy in rice. Thereby, photosynthetic activation of BS cells must be developed before the CO2 shuttle toward the BS cells can establish. However, very little is known about the genes controlling the BS cell size and BS chloroplast development in C4 plants. To study them an EMS based forward genetic screen was performed in the C3 model plant Arabidopsis thaliana by taking consideration of the fact that the gene regulatory networks of the BS cells in the C3 and C4 dicotyledons plants are at least partly conserved. The BS cells of the Arabidopsis plants were labeled with the chloroplast-targeted green fluorescent protein (sGFP) using a BS cell-specific promoter. Differences in the reporter gene signal intensity in the Arabidopsis leaf served as a proxy for collecting mutant lines with possible altered BS cell anatomy. To this end, 10 stable EMS mutant lines were identified that showed an increased or a decreased GFP signal intensity compared to the non-mutagenized reference line. A high-resolution light microscope analysis on the six mutant lines showed that three of these mutants have an effect in the BS cell number and size of the vasculature. This study identified mutant lines with affected BS cells, and therefore it sets a good background for future research to identify genes involved in the BS cell ontogeny and maintenance.
Lizenz:	Urheberrechtsschutz
Fachbereich / Einrichtung:	Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie » Entwicklungs- und Molekularbiologie der Pflanzen
Dokument erstellt am:	07.01.2019
Dateien geändert am:	07.01.2019
Promotionsantrag am:	14.09.2018
Datum der Promotion:	17.12.2018