Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


osu1211899658.pdf (13.9 MB)

ETD Abstract Container

Abstract Header

Genetic manipulation of NADPH: Protochlorophyllide Oxidoreductase content in Arabidopsis reveals essential roles in prolamellar body formation and plant development

Paddock, Troy N.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1211899658

Abstract Details

2008, Doctor of Philosophy, Ohio State University, Plant Biology.
Chlorophyll synthesis in angiosperms requires light because, in contrast to other photosynthetic organisms, they rely exclusively on a light-dependent mechanism to reduce protochlorophyllide during chlorophyll biosynthesis. NADPH:protochlorophyllide oxidoreductase (POR) catalyses a light-dependent reduction of protochlorophyllide to chlorophyllide, which is subsequently transformed to chlorophyll. In etioplasts during skotomorphogenesis, POR forms a photolabile aggregate of NADPH-POR-Pchlide localized to the prolamellar bodies. In Arabidopsis there is a three-member gene family encoding structurally related but differentially regulated POR enzymes denoted PORA, PORB and PORC. PORA and PORB accumulate during skotomorphogenesis. PORB and PORC accumulate during seedling development and throughout the life of the plant, during which they are responsible for bulk chlorophyll synthesis. Here I describe the detailed molecular-genetic dissection of the functions of the different POR isoforms. While single porB-1 or porC-1 null mutants display no distinct light-grown phenotypes, the porB-1 porC-1 double mutant displays a severe xantha (highly chlorophyll-deficient) phenotype. In response to illumination, chlorophyll production, thylakoid stacking and photomorphogenesis are restored in the PORA-overexpressing porB-1 porC-1 transgenic lines. Therefore, the porB-1 porC-1 double mutant is functionally rescued by ectopically expressed PORA, which suffices in the absence of either PORB or PORC to direct bulk chlorophyll synthesis and normal plant development. Using reverse genetic approaches, our lab identified a porA-1 null mutant which I have characterized here; additionally I have characterized PORA RNAi knockdown lines. The porA-1 and PORA RNAi lines display photoautotrophic growth blocks which are partially rescued on sucrose-supplemented media. porA-1 mutant seedlings display defects in etioplast development with reductions in prolamellar body accumulation and photoactive Pchlide conversion. Further analysis of the porB-1 porC-1 double null mutant reveals independent PORA catalytic activity in the cauline leaves of low-light grown plants. The porA-1 porB-1 and porA-1 porC-1 double mutants were used investigate the contributions of each POR individual isoform to Chl biosynthesis and growth in green plants. The porA-1 porB-1 and porA-1 porC-1 mutants have photoautotrophic growth defects which resemble that of the porA-1 single mutant. In addition, etioplast development in the porA-1 porB-1 double mutant is defective, with no detected prolamellar body formation or photoactive protochlorophyllide conversion.
Greg Armstrong, PhD (Advisor)
Randy Scholl, PhD (Committee Member)
Patrice Hamel, PhD (Committee Member)
Lamb Rebecca, PhD (Committee Member)
170 p.
Biology; Cellular Biology; Molecular Biology

Recommended Citations

Citations

  • Paddock, T. N. (2008). Genetic manipulation of NADPH: Protochlorophyllide Oxidoreductase content in Arabidopsis reveals essential roles in prolamellar body formation and plant development [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1211899658

    APA Style (7th edition)

  • Paddock, Troy. Genetic manipulation of NADPH: Protochlorophyllide Oxidoreductase content in Arabidopsis reveals essential roles in prolamellar body formation and plant development. 2008. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1211899658.

    MLA Style (8th edition)

  • Paddock, Troy. "Genetic manipulation of NADPH: Protochlorophyllide Oxidoreductase content in Arabidopsis reveals essential roles in prolamellar body formation and plant development." Doctoral dissertation, Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1211899658

    Chicago Manual of Style (17th edition)

osu1211899658
671
© 2008, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.