Senescence is the final developmental stage of a plant leaf, which occurs as the organ reaches the end of its natural lifecycle. In this process, photosynthetic machinery is broken down and recycled as nutrients for use in the rest of the plant. This allows the recovery of the resources invested in the plant leaves as the plant transitions to a reproductive state. While a developmentally controlled process that occurs naturally as the organ ages, leaf senescence can also be induced prematurely by environmental stresses. The onset of senescence facilitates survival of the plant as a whole at the cost of leaf tissue. As such, senescence is controlled by regulatory systems that cross link developmental and stress response signals. One such signalling mechanism is the action of transcription factors. The NAC family transcription factor ANAC092 has been shown to promote the onset and progression of senescence during developmental and stress conditions. Timeseries gene expression data and network inference indicated ANAC092 as being a central hub in the stress response to Botrytis cinerea infection. ANAC092 was shown to be a functional gene during Botrytis cinerea infection, promoting the spread of lesions through the onset of a senescence like process. As such, ANAC092 represents a major cross-link between developmental and pathogenic stress response signals. A number of transcription factors bound to the ANAC092 promoter region in a yeast 1-hybrid experiment, including members of the NAC, MYB, ERF and AtHB transcription factor families. Interestingly, members of the same transcription factor family co-localised to regions of the ANAC092 promoter, suggesting they recognised similar sequences. Gene expression profiles and network inference were used to generate a model of regulation by these transcription factors. It was predicted certain transcription factors would regulate ANAC092 expression during specific conditions. In particular, different members of the NAC family of transcription factors appeared to regulate ANAC092 expression during Botrytis cinerea infection or developmental senescence. These predictions were tested using transgenic Arabidopsis. The NAC transcription factor recognition sequence is known for a limited subset of NAC transcription factors. In an attempt to define the binding motif for a higher proportion of the NACs, a yeast 1-hybrid library of 94 NAC transcription factors was constructed and screened against a range of Arabidopsis promoter regions. Binding motifs were reverse engineered and tested for NAC protein binding.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:647969 |
| Date | January 2014 |
| Creators | Talbot, Adam R. |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/67661/ |
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