While our knowledge of the functional properties of eukaryotic cellular organelles is quite comprehensive, the mechanisms by which organelles achieve their varied shapes remain poorly understood. By categorising the components which contribute to the architecture of the cell, relationships between structure and function can be established. Many mechanisms have been proposed which try to account for the shape and structure of complex organelles such as mitochondria and, more recently, the endoplasmic reticulum (ER); an organelle which comprises multiple domains, both structurally and functionally. Recently, a class of membrane proteins – the reticulons – have received renewed attention as they are thought to shape the tubular ER through their wedge-like insertion into the lipid bilayer and the formation of scaffolds through homo- and hetero-oligomerisation. Reticulons and reticulon-like proteins have been implicated in many cellular processes and have key roles in many disease states – for which they have received much attention. As much of the research on reticulons has focused on mammals and yeast, the functions of reticulons in plants are poorly characterised. The model organism, Arabidopsis thaliana, contains 21 reticulon genes, expressed throughout all tissues and developmental stages of the plant. This thesis focuses on the ER-shaping properties of a seed-specific reticulon - RTNLB13. Its expression and unique topology were found to contribute to the formation of ER tubules in plants by inducing curvature in the ER membrane. RTNLB13 is restricted to tubular ER and its over-expression induces constrictions within the ER membrane which affects both soluble and membrane protein diffusion. RTNLB13 sits in a ‘w’ conformation in the membrane with its N- and C-termini facing the cytosol. The length and orientation of its transmembrane domains play an important role in protein localisation and inducing membrane curvature. In its native organism, Arabidopsis thaliana, RTNLB13 is expressed during the late stages of embryonic maturation, although a rtn13 knockout yielded no observable phenotype.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:524980 |
| Date | January 2010 |
| Creators | Tolley, Nicholas Joseph |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/3802/ |
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