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Harnessing the anabolic properties of dark respiration to enhance sink activity at elevated CO2 using Arabidopsis thaliana L. with partially-suppressed mitochondrial pyruvate dehydrogenase kinase

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dc.contributor.advisor Micallef, Barry
dc.contributor.advisor Grodzinski, Bernard Weraduwage, Sarathi 2013-05-17T15:40:01Z 2013-05-17T15:40:01Z 2013-04 2013-04-25 2013-05-17
dc.description.abstract Sink limitations in plants reduce the potential for photosynthesis and yield, particularly under conditions that favour enhanced source activity such as elevated CO2 (EC). Dark respiration, considered catabolic, has rarely been exploited to enhance sink activity in plants. Arabidopsis thaliana L. lines with partially-suppressed mitochondrial pyruvate dehydrogenase (mtPDH) kinase (mtPDHK), a negative post-translational regulator of the mtPDH complex, was shown previously to have both elevated mtPDH complex activity and increased seed weight and oil content at ambient CO2 (AC), suggesting an enhancement of sink activity. The mtPDH links glycolysis with the tricarboxylic acid (TCA) cycle. It was hypothesized that Arabidopsis having suppressed mtPDHK will display their greatest plant productivity at EC through a combined enhancement of source and sink activities. Control and transgenic Arabidopsis having either constitutive or seed-specific expression of antisense mtPDHK were grown at either AC or EC. Expression of mtPDHK and mtPDH complex activity in rosette leaves and reproductive tissues were measured, which required the development of an assay to quantify mtPDH activity. Vegetative and reproductive growth over time, seed oil parameters, and leaf net C exchange were also quantified. A parabolic relationship was found between mtPDHK expression and mtPDH activity, reflecting a role for mtPDH in balancing photosynthetic and respiratory processes. A number of growth and seed oil parameters were improved in transgenic lines, particularly at EC; many of these parameters showed a significant linear or quadratic correlation with mtPDHK expression and mtPDH activity. The proportion of very long chain fatty acids was increased in transgenic lines. Leaf net C exchange was enhanced at AC and EC, and particularly in lines showing repression of mtPDHK. The greatest enhancement in total seed and oil productivity was found for the constitutive lines 104 and 31 at EC (up to 2.8 times). These two lines exhibited a significant increase in inflorescence size, an increase in leaf water use efficiency, the lowest rate of mtPDH complex inactivation by ATP, and an intermediary enhancement of mtPDH complex activity in seeds. Thus, it is concluded that the mtPDH plays a key role in regulating sink and source activities in plants. en_US
dc.description.sponsorship Natural Sciences and Engineering Research Council (NSERC) through the Green Crop Networks Research Network; Ontario Graduate Scholarship; Syngenta Graduate Scholarship; Ball Farm Services and Agrico Canada Ltd. Scholarship; Mrs. Fred Ball Scholarship; Arthur D. Latornell Scholarship; Hoskins Scholarship; Robb Travel Grant; Registrars and the Deans Scholarship and travel awards and bursaries from the University of Guelph, and the Ontario Agricultural College. en_US
dc.language.iso en en_US
dc.rights Attribution-NonCommercial-NoDerivs 2.5 Canada *
dc.rights.uri *
dc.subject Anabolic en_US
dc.subject Catabolic en_US
dc.subject Sink activity en_US
dc.subject Source activity en_US
dc.subject Mitochondrial pyruvate dehydrogenase en_US
dc.subject Mitochondrial pyruvate dehydrogenase kinase en_US
dc.subject Elevated CO2 en_US
dc.subject Dark respiration en_US
dc.subject TCA cycle en_US
dc.subject Arabidopsis thaliana en_US
dc.subject Oil synthesis en_US
dc.subject Fatty acid synthesis en_US
dc.subject Photosynthesis en_US
dc.subject Harvest index en_US
dc.title Harnessing the anabolic properties of dark respiration to enhance sink activity at elevated CO2 using Arabidopsis thaliana L. with partially-suppressed mitochondrial pyruvate dehydrogenase kinase en_US
dc.type Thesis en_US Plant Agriculture en_US Doctor of Philosophy en_US Department of Plant Agriculture en_US

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