Graduation Term

2024

Degree Name

Master of Science (MS)

Department

School of Biological Sciences

Committee Chair

Viktor Kirik

Abstract

Plants cells are fixed in place. As a result they have to carefully divide in order to function properly. Plants use a number of complex microtubule arrays to ensure proper division and orientation including the preprophase band (PPB) and the phragmoplast. The PPB orients the cell prior to division and marks the cortical division site, which is where the phragmoplast is guided to. The phragmoplast is a dynamic microtubule array that builds the cell plate which later becomes the cell wall that divides daughter cells. Proteins involved with PPB formation include Tonneau1 (TON1) and Tonneau2 (TON2) which localize to and are involved in PPB formation. When these proteins are disrupted plant cells have irregular shapes and the plant are infertile. The Tonneau1 Recruiting Motif (TRM) is a superfamily of 34 different proteins. TRMs 6, 7, and 8, have been shown to have a role in cell morphogenesis and localize to the PPB. It is possible that similarly structured TRMs 23, 24, 25, and 16, 32 may play redundant functions. Ungrouped TRMs 30 and 34 are also be examined due to having a similar motif organization. To determine the function of these proteins they were localized using both nonnative and the corresponding native promoters. Mutant lines have been obtained and used make multiple knockouts in the same TRM subfamilies. Additionally, TON2 characteristics are studied using mislocalization with Calcium Dependent Protein Kinase 34 (CPK34) plasma membrane-targeting domain to support the existence of a TON2:TON1:TRM complex. Additional properties of TON2 are studied including 1) the presence of a potential nuclear localization signal (NLS); 20 interactions with kinases IRK and IRKI, which resembles Gravitropic in the Light 1 (GIL1) which interacts with TON2. We show that 1) TRMs 23, 24, and 25 localize to the PPB; 2) TRM 30 and 34 are microtubule associated proteins (MAPs); 3) TRM 32 localizes to the plasma membrane; 4) expressing TRMs using their native promoters results in tissue specific expression. However, creating mutant lines using T-DNA has not resulted in an observable phenotype. Additional, using a yeast two-hybrid assay we have shown that TON2 does not interact with IRK or IRKI, that deletion of the predicted NLS site resulted in protein destruction, and mislocalization of TON2 does not rescue the ton1 mutant phenotype.

Access Type

Thesis-Open Access

DOI

https://doi.org/10.30707/ETD2024.20240827063556875631.999988

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Available for download on Wednesday, August 19, 2026

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