Dissertation
Physiological and biochemical analysis of transgenic rice over-expressing C4 genes from maize and the diversity and plasticity of C4 photosynthesis in Eleocharis (Cyperaceae)
Washington State University
Doctor of Philosophy (PhD), Washington State University
05/2007
DOI:
https://doi.org/10.7273/000005779
Abstract
From a photosynthetic point of view, yield of some crops may be further
improved by increasing the photosynthetic capacity of the source leaves and/or by
increasing partitioning of photoassimilate to organs of economic importance. C4 plants
are able to overcome photorespiration, and thus photosynthesize more efficiently, through
an additional photosynthetic pathway (C4) and specialized leaf anatomy (Kranz) that
work together as a "CO2 pump" to supply Rubisco with enriched CO2 edging out O2 as a
competitive substrate. This photosynthetic mechanism endows C4 plants a selective
advantage over C3 plants especially in warmer climates and during water deficits: higher
photosynthetic capacity, and higher water and nutrient use efficiency. The C4 syndrome is
characterized by high activities of C4 enzymes and Kranz anatomy (mesophyll and
bundle-sheath cells). Traditionally, Kranz anatomy, which allows for the spatial
separation of the C4 biochemical steps, was believed to be required for the C4 CO2
concentrating mechanism in terrestrial plants. However, it is known that C4-like
mechanisms can be induced, without the presence of Kranz anatomy, in two submersed
v
aquatic species (Hydrilla verticillata and Egeria densa). Most recently, the terrestrial C4
plants Bienertia cycloptera, B. sinuspersici, and Suaeda aralocaspica (Chenopodiaceae)
from Central Asia have been found to lack Kranz anatomy and function with specialized
intracellular compartmentation. Thus, by introducing the necessary genes of the C4
pathway to C3 plants, it may be possible to engineer a C4-like mechanism and improve
photosynthesis without a requirement for Kranz anatomy. In this study, C3 rice was
transformed with two genes encoding C4 photosynthetic enzymes (phosphoenolpyruvate
carboxylase and pyruvate orthophosphate dikinase) and the photosynthetic, biochemical,
and anatomical changes were documented.
Additionally, research with the genus Eleocharis shows that the C4 syndrome may
be more plastic than formerly believed. Within the genus, species were shown to possess
the full range from C3 to intermediate to C4. In a species dependant manner, plants
changed photosynthetic types whether grown terrestrially or submerged with concomitant
changes in the C4 enzyme activities, carbon isotope composition and leaf anatomy.
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Details
- Title
- Physiological and biochemical analysis of transgenic rice over-expressing C4 genes from maize and the diversity and plasticity of C4 photosynthesis in Eleocharis (Cyperaceae)
- Creators
- Lesley Ryann Murphy
- Contributors
- Gerald E Edwards (Chair) - Washington State University, School of Biological SciencesEric Roalson (Committee Member) - Washington State University, School of Biological SciencesAndrew McCubbin (Committee Member) - Washington State University, School of Biological Sciences
- Awarding Institution
- Washington State University
- Academic Unit
- School of Biological Sciences
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 158
- Identifiers
- 99901054760301842
- Language
- English
- Resource Type
- Dissertation