The transition to flowering is one of the major and important phase changes during the plant’s life cycle. It has been shown that multiple signalling pathways are involved in this process. Many of these pathways converge on the floral integrator gene FT. FT is activated in the leaves by an inducing signal (e.g. photoperiod) and then it moves to the shoot apex. At the apex, the FT protein interacts with FD to initiate floral development through transcriptional activation of APETALA1 and SOC1. Several papers have reported that the FT protein moves from leaf to the shoot apex and acts as the flowering stimulus. However, it is not clear whether FT mRNA may also move through the phloem and contribute to the long-distance movement of FT. This study investigated whether FT mRNA has the capacity for long-distance movement, which cis-element(s) is responsible for its mobility and what is the biological significance of FT RNA movement. It also examined which amino acid residue(s) or domain(s) are critical for FT protein function. Utilizing an RNA mobility assay and virus induced RNA silencing, it has been found that FT mRNA, independent of the FT protein and viral sequences, is able to move systemically in Nicotiana benthamiana and Arabidopsis plants. FT RNA also can enter into the shoot apical meristem of tobacco plants. Moreover, the cis–acting element essential for FT RNA movement has been mapped to nucleotides 1-102 of the FT mRNA coding sequence. A protein which specifically binds to FT mRNA only in the vegetative stage of plant development has been identified, suggesting that the FT RNA-protein interaction may be developmentally modulated. Ectopic expression of FT mRNA triggers flowering earlier than wild type plants in inductive short day conditions, suggesting that FT mRNA might also plays a promotory role in floral induction. Using alanine-scaning mutagenesis, 43 FT mutants were constructed using PVX vector and used to inoculate tobacco plants. Viral expression of these FT mutant proteins in N. tabacum Maryland Mammoth tobacco plants resulted in various flowering phenotypes. Analysis of these phenotypes showed that mutant FTV70A stimulated slightly early flowering and significantly improved the number of flowers and seedpods. This raises the possibility that novel FT alleles could be used to speed up breeding process and improve the productivity of crops.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:537753 |
| Date | January 2011 |
| Creators | Li, Chunyang |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/36849/ |
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