Date of Award
Master of Science (MS)
School of Biological Sciences
In plants, the cell wall makes cell migration impossible so plants must carefully control the orientation of cell division to ensure proper tissue development. Before prophase, the division plane is marked by formation of the preprophase band (PPB) which disassembles at the onset of prometaphase. During cytokinesis, the cell plate localizes to the division plane and attaches to the cell wall where the PPB was located. The proteins Tonneau 1 (TON1), Tonneau 2 (TON2), and the Tonneau 1 Recruiting Motif (TRM) family may be involved in the regulation of cell division orientation and PPB formation as plants with mutations in these genes fail to form a PPB and show aberrant cell division. It is possible that TRMs may be involved in intracellular targeting. A subset of TRMs containing the M3 motif (TRMs 12, 13, 14, 15, and 18) are homologous with phosphatidylinositol n-acetylglucosaminyltransferase-P (PIG-P). An addition TRM (TRM33) shows homology with PIG-P but lacks the M3 motif. The role of the M3 motif was investigated by deleting the motif from TRM13 and inserting it into TRM33. To identify the function of these proteins, multiple knockout and overexpression lines were created and analyzed for changes in phenotype or localization. TRM overexpression resulted in under-branched trichomes, and the degree of under-branching varied with the presence of the M3 motif. Differences in the charge profile of the M3 motif correlated with degree of under-branching with a stronger negative charge at the C-terminus was correlated with increased under-branching. There was no discernable change in localization related to the presence of the M3 motif. However, PPB localization was not observed in TRM33 and no PPB marker was present, so the results of the localization experiment were inconclusive. It was discovered that TRM18 localizes to the nuclear membrane and may be involved in microtubule organization there. Quadruple knockout mutants showed no aberrant phenotype, and quintuple mutants will be verified in the F3 generation. It was not possible to create a quadruple mutant containing trm12, and it has been suggested that trm12 may be deleterious in the presence of trms 13 and/or 14.
Zare-Mehrjerdi, Omid John, "Functional and Structural Characterization of TRMs" (2021). Theses and Dissertations. 1585.
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