The sensing and integration of environmental cues is of crucial significance to plants. Particularly important for these photoautotrophic organisms is the use of light as an informational signal. The presence of potentially-shading neighbours can be perceived by plants using specialised photoreceptors. This activates a switch to a developmental programme characterised by stem elongation growth and early flowering. Collectively, these responses are known as the 'shade-avoidance response'. One of the key triggers of shade-avoidance is a reduction in ratio of red: far-red light (R: FR) perceived by the plant. At a molecular level, low R: FR light promotes the stabilisation and activation of a class of transcription factors termed PHYTOCHROME INTERACTING FACTORS (PIFs). These promote the expression of auxin biosynthesis genes which then leads to stem elongation growth. In this thesis I show that UV-B, sensed by the newly characterised UV-B photoreceptor UV-RESISTANCE LOCUS 8 (UVRB), provides a strong brake on low R: FR-induced shade-avoidance across the entire Arabidopsis life cycle. This is achieved by a dual mechanism which results in both the inactivation of PIFs, potentially through competitive binding by DELLA proteins, and a direct destabilisation of PIF proteins. UV-B thus inhibits the upregulation of auxin activity usually induced by low R: FR conditions, thereby limiting stem elongation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:685352 |
| Date | January 2015 |
| Creators | Hayes, Scott |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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