Aquaporins are membrane channels transporting water and small molecules across the membranes of various intracellular compartments. Plant aquaporins constitute the Major Intrinsic Protein (MIP) family, consisting of 35 members in Arabidopsis thaliana, all exhibiting expression patterns which are specific in tissue type and developmental timing. Aquaporins are thought to be vital to plant growth, development, and response to drought. However, little work has been done to clarify the exact roles of particular isoforms in each of these aspects. The MIP isoforms TIP3;1 and TIP3;2 are uniquely localised to both the plasma membrane and tonoplast. In addition, they are the only aquaporins present in the maturing and germinating Arabidopsis seeds. Their potential importance in these developmental processes has therefore been speculated, but is yet to be fully elucidated. In addition, it is suspected that a C-terminal domain unique to TIP3 isoforms is responsible for their plasma membrane localisation. However little has been done to dissect the cellular sorting route they take, or the order in which they reach both membranes. By misexpressing MIP isoforms, including TIP3, in transgenic Arabidopsis and systematically assessing the resulting effect on germination and seedling growth in water limiting conditions, it was found that increased expression of Arabidopsis thaliana aquaporin isoforms at atypical developmental time points can confer drought tolerance in both germination and seedling growth. More specifically, increasing the number of aquaporins at the plasma membrane can enhance tolerance to drought during germination, implying a fundamental role for the dual localisation of TIP3 at this developmental stage. Fluorescent protein fusions to TIP3 were employed to dissect the order of this isoform’s trafficking, and pharmacological techniques confirmed the route. From this, an inducible expression system for TIP3 has been established to study dual sorting, and TIP3 were confirmed to traffic independently of the Golgi complex in embryonic tissues, regardless of the presence or absence of their C-terminal motif.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:640948 |
| Date | January 2014 |
| Creators | Carroll, Charlotte Elizabeth Ella |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/66471/ |
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