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      • HARVEST
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      SCREENING AND CHARACTERIZATION OF ARABIDOPSIS THALIANA MUTANTS WITH ALTERED CAROTENOID PROFILE

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      NARAYANAN-DISSERTATION.pdf (6.301Mb)
      Date
      2014-08-27
      Author
      Narayanan, Karthikeyan
      Type
      Thesis
      Degree Level
      Doctoral
      Metadata
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      Abstract
      Carotenoids are organic pigments that are mainly found in the chloroplasts and chromoplasts of plants and other photosynthetic organisms. Carotenoid molecules containing oxygen, such as lutein, violaxanthin and zeaxanthin are called xanthophylls and the rest containing un-oxygenated carotenoids are known as carotenes. Carotenoids form the integral part of the photosystem II LHC. Xanthophylls mainly aid in light harvesting and dissipation of harmful excess energy from excited chlorophyll molecules, thereby protecting chlorophyll from photo-degradation. The biosynthesis of carotenoids has been widely studied using plant and algae. However, the regulatory mechanisms involved in carotenoid metabolism need better understanding. This thesis identified novel regulatory mechanisms involved in the carotenoid biosynthetic pathway using activation-tagged Arabidopsis mutants. Two screening methods, red seed coat screening and norflurazon resistance screening, were used in this study. Fourteen mutants were screened using red seed coat screening but a successful mutant characterization could not be performed due to the unavailability of mutants with a single copy T-DNA insertion. Norflurazon screening identified eight mutants, out of which two mutants, KN203 and KN231, were characterized. The KN203 mutant had a defective keto-acyl CoA synthase 19 gene. KN203 mutant had lower carotenoid levels in the leaves and increased carotenoid levels in the mature seeds; the mutant was able to revert back to wild type phenotype after complementation of a functional KCS19 gene copy driven by native promoter. The fatty acid analysis indicated that the mutant KN203 had decreased MGDG and increased lysoPG, lysoPC and lysoPE content. Reduced carotenoid content in KN203 leaves was attributed to changes in fatty acid composition of chloroplast envelope membrane. Mutant KN231 had a T-DNA insertion in a gene encoding a RNA binding protein (RBP47C). KN231 leaf carotenoid levels were similar to wild type but their levels were significantly higher in their seeds. Two allelic mutants were selected to characterize the mutants. Overexpression of functional RBP47C in the mutants reverted to wild type phenotype in some overexpression mutants. A tandem repeat homologue of RBP47C, RBP47C’was identified. In-silico analysis predicted RBP47C to be a potential candidate for chloroplast localization.
      Degree
      Doctor of Philosophy (Ph.D.)
      Department
      Food and Bioproduct Sciences
      Program
      Applied Microbiology
      Supervisor
      Khachatourians, George; Gruber, Margie
      Committee
      Hegedus, Dwayne; Gray, Gordon; Qiu, Xiao
      Copyright Date
      June 2014
      URI
      http://hdl.handle.net/10388/ETD-2014-06-1601
      Subject
      Carotneoids, RBP47, KCS19, Gene expression, Gene regulation,
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