Date on Master's Thesis/Doctoral Dissertation

5-2022

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Biology

Degree Program

Biology, PhD

Committee Chair

Running, Mark

Committee Member

Perlin, Michael

Committee Member

Sandell, Lisa

Committee Member

Schultz, David

Committee Member

Hwangbo, Dae-Sung

Author's Keywords

physcomitrium patens; arabidopsis; prenylation; gene knockdown; bioethanol; plant biomass

Abstract

This dissertation is an examination and characterization of the functional roles of PPAL. PROTEIN PRENYLTRANSFERASE ALPHA SUBUNIT-LIKE (PPAL) is a recently discovered gene. PPAL homologs are present in all plants and many animals, where its function is largely unknown. It is possible that PPAL could participate in prenylation processes since it shares similarity to the α subunits of known prenylation enzymes. Prenylation is a post-translational modification of proteins that involves the addition of a lipid moiety to proteins to facilitate membrane targeting and association and promote protein-protein interactions. Prenylation has important roles in plant growth and development, including cell elongation, cell differentiation, and cell identity determination. In moss there are two PPAL homologs, PpPPAL1 and PpPPAL2, and the disruption of either results in lethality. To study the functional role of PpPPAL, we used targeted gene knockdown through artificial miRNA followed by genotypic and developmental studies in Physcomitrium patens. First, we found that PpPPAL has roles in cell differentiation, cell expansion, polar cell elongation, organization of the cytoskeleton, and response to hormones and external stimuli. Plant growth and development must be continuously adjusted to respond to available resources. The ability to sense the resources require the integration of signals conveying the plant metabolic status, its growth and developmental stage, and hormonal balance. Sugar sensing and signaling is vital to integrate internal regulators and environmental cues to govern and sustain plant growth and survival. We studied the ability of PpPPAL to sense and respond to external stimuli. We showed that PpPPAL is a potential glucose sensor and/or regulator in the plant glucose signaling network as well as a potential overall energy sensor. Environmental concerns surrounding the overuse of natural gas and petroleum, the excessive greenhouse gas (GHG) emission, and global warming has led to the search for sustainable bioenergy sources, such as biomass feedstock, for creating profitable biorefineries and facilitating bioeconomy. We characterized and proposed the moss Physcomitrium (Physcometrilla) patens as a potential biomass feedstock for biofuel production. These studies help elucidate some of the functional roles of PpPPAL in plant biology and development and suggest ways to use moss biomass in the emerging economy.

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