Cellulose Biosynthesis from a Product and Machinery Perspective
Restricted (Penn State Only)
- Author:
- Frank, Mark Allen
- Graduate Program:
- Biochemistry, Microbiology, and Molecular Biology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 26, 2024
- Committee Members:
- William Hancock, Outside Field Member
Matthew Swulius, Outside Unit Member
Manish Kumar, Special Member
B Nixon, Chair & Dissertation Advisor
Joyce Jose, Major Field Member
Santhosh Girirajan, Program Head/Chair
Jean-Paul Armache, Major Field Member - Keywords:
- Cellulose
Cellulose Synthase
Cellulose Microfibril
Electron Tomography
Mutagenesis
Physcomitrium patens - Abstract:
- Cellulose, the most abundant biopolymer, plays an integral role in the biology of plants. Despite its chemical simplicity, a chain of glucose molecules joined to one another by a beta-linkage between atom 1 and 4 of the anomeric ring, cellulose exhibits emergent properties as a consequence of the biomolecular machinery that synthesizes it at the plasma membrane of plants, bacteria, and even some animals. Recently, these molecular machines, cellulose synthases, have been solved to high resolution using x-ray crystallography and single particle cryogenic electron microscopy. Despite these advances, a complete understanding of the structure/function of cellulose synthase in the context of their larger oligomeric complexes remains elusive. In these pages, an application of cryo-electron tomography and subtomogram averaging is shown to reveal a previously unreported helical organization of cellulose microfibrils, an application of the Deep Analysis of Residue Constraints (DARC) bioinformatic method makes novel predictions of amino acids for how bacterial and plant cellulose synthases function, and preliminary testing of these predicted, significant residues through the application of site-directed mutagenesis of CesA5 within the model moss Physcomitrium patens. As part of the latter set of studies, genetic disruption or removal of a newly hypothesized tethering function that residues in the amino-terminal 25 residues of CesA5 and other CesAs is found to prevent the gene’s ability to complement a cesA5 deletion strain of P. patens. The impact of helical packing of cellulose microfibrils, the identification of new mutagenic targets for functional studies of CesAs, and the now confirmed presence of a crucial NT-motif in CesAs are discussed in terms of how they impact our understanding of cell wall construction in plants. Understanding how cellulose synthases produce cellulose could potentially allow for the rationale engineering of these enzymes toward making altered cellulose.