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DYNAMICS AND FUNCTIONS OF PLASTID LIPOPROTEIN PARTICLES

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Abstract

Plastoglobules (PGs) are highly dynamic monolayer lipoprotein particles in chloroplasts and other plastid types in higher plants. PGs have important roles in plastid biogenesis/homeostasis, senescence, and abiotic stress responses. Their specialized proteome consists of ~30 proteins and a metabolome enriched for isoprenoids, such as vitamin E and various quinones. The PG proteome includes six atypical ABC1 kinases (K1,3,5,6,7,9), tocopherol cyclase (VTE1), and various proteins with unknown functions. These PG localized proteins strongly co-express with other proteins involved in a narrow subset of plastid functions, suggesting that PGs are a regulatory hub and micro-compartment of several plastid processes. Indeed, it was previously shown that K1 and K3 physically interact, and (in)directly regulate VTE1 activity and metabolic content of PGs. This thesis research shows that seed longevity is decreased in higher order ABC1K mutants, which may indicate isoprenoid deficiency, including vitamin E. However, molecular mechanisms through which ABC1K proteins affect isoprenoid metabolism are poorly understood. Various lines of evidence suggest that K6 genetically interacts with K1 and K3 and may share functions. Phenotyping of higher order k1, k3, and k6 mutants determined their molecular functions related to seed longevity and oxidative stress response. Comprehensive mRNA-based co-expression network analysis based on public micro-array and RNAseq data inferred and improved the understanding of PG functions, specifically that PG core proteins have a larger role in redox regulation than originally hypothesized. Co-expression network analysis combined with proteomics identified 11 new PG core and recruited proteins. In addition to the six PG localized PG proteins, the Arabidopsis genome encodes for an additional 11 ABC1K proteins. Structural modeling and co-expression analysis were employed to better understand this enigmatic protein family protein. K4 and K12A were found to have functions related to plastid biogenesis and plastid protein homeostasis related, respectively. This thesis provides new insights in how these dynamic monolayer micro-compartments contribute to chloroplast metabolism and homeostasis.

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167 pages

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2020-08

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Keywords

ABC1 kinases; chloroplast; plastoglobule; thylakoid

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Union Local

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Committee Chair

Wijk, Klaas Van

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Hanson, Maureen R.
Hua, Jian

Degree Discipline

Plant Biology

Degree Name

Ph. D., Plant Biology

Degree Level

Doctor of Philosophy

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Government Document

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Attribution 4.0 International

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dissertation or thesis

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