The Regulation of Arabidopsis thaliana Stem Development by IQ67-Domain Proteins

Yates, Bryony (2026) The Regulation of Arabidopsis thaliana Stem Development by IQ67-Domain Proteins. Doctoral thesis, University of East Anglia.

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Abstract

Early plant anatomists noted that different plant tissues exhibit contrasting patterns of cell division, often juxtaposed against each other (Sachs 2011 [1875]). In some regions of the shoot apical meristem (SAM), for example, the angles of new cell walls are highly variable, while other regions have regimented cell wall orientation (Bencivenga et al. 2016). The tight regulation of these cell division patterns implies that cell wall orientation is important for plant morphogenesis. However, the relationship between division orientation and morphogenesis is poorly understood, because many mutants with wall orientation defects have either remarkably normal growth or complex pleiotropic phenotypes (Spinner et al. 2013; Kirik et al. 2012; Schaefer et al. 2017). Furthermore, we have an incomplete understanding of how division orientation is regulated: many signals that direct cell wall orientation have been identified, but the mechanisms and molecular components that perceive and translate them into robust cell wall positioning are not well-characterised.

The plant-specific IQ67-domain (IQD) genes encode a large family of calmodulin-binding proteins that are implicated in the regulation of morphogenesis. At the cellular level, IQDs regulate microtubule organisation and are proposed to act as scaffolds for intracellular signalling (Abel et al. 2013; Bürstenbinder, Mitra, et al. 2017). Here I report that members of the 1A subfamily of Arabidopsis IQDs localise to mitotic structures, including the preprophase band (PPB), cortical division zone (CDZ), and cell plate. Loss of function of the entire 1A subfamily (6 genes) impairs the orientation of new cell walls specifically in the pith-producing region of the SAM and increases the thickness of the plant stem. I propose that, in wild type plants, 1A IQDs are recruited to the PPB/ CDZ to ensure robust division plane positioning, while misoriented divisions in loss-of-function mutants drive radial stem growth by increasing the number of pith cell files. These results highlight how changes to cell division orientation can drive differential organ growth and identify novel molecular regulators of cell division orientation.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	26 Feb 2026 09:07
Last Modified:	26 Feb 2026 09:07
URI:	https://ueaeprints.uea.ac.uk/id/eprint/102072
DOI:

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