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Regulation of juvenility in Antirrhinum majus
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Sgamma, Tiziana (2012) Regulation of juvenility in Antirrhinum majus. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk:80/record=b2580203~S1
Abstract
Floral initiation is regulated by an elaborate network of signalling pathways, including the
photoperiodic pathway. In Arabidopsis, flowering is promoted through this pathway by activation
of FLOWERING LOCUS T (FT) by CONSTANS (CO) in long days. During juvenility plants are
incapable of flowering in response to environmental conditions that would normally be
favourable.
This project studies the molecular basis of floral incompetence during juvenility in the
model annual species, Antirrhinum majus and the important commercial tree species, Olea
europaea, which has an extended juvenile phase.
Photoperiod transfer experiments were used to measure the length of juvenility in plants
grown in controlled environment cabinets at different Daily Light Integrals. Analysis of
Antirrhinum FT (AmFT) expression during development showed that AmFT expression is
minimal during juvenility and increases in all leaves following the end of the juvenile phase. The
photoperiodic pathway was shown to be active during juvenility, suggesting that an additional
mechanism involving the repression of FT could be involved in the regulation of juvenility.
Full length Antirrhinum and Olive cDNAs representing homologues of the Arabidopsis FT
repressors TEMPRANILLO 1 (AtTEM1) and AtTEM2, which act antagonistically with CO, were
isolated. Molecular and phylogenetic analyses revealed high amino acid identities between
Antirrhinum (AmTEM) and Olive (OeTEM) TEM-like proteins and AtTEM1 & 2. AmTEM and
OeTEM proteins contain AP2 and B3 domains, consistent with AtTEM1 and AtTEM2, and can
be classified as Class I members of the RAV sub-family of B3 transcription factors.
AmTEM and OeTEM expression levels were shown to be higher during juvenility
suggesting a potential role for TEM in controlling juvenility. A reciprocal relationship between
expression levels of AmTEM/AtTEM1 and AmFT/AtFT was revealed in both Antirrhinum and
Arabidopsis. Analysis of expression across development showed that AmTEM/AtTEM1 levels
decline at around the time juvenility ends corresponding to when AmFT/AtFT levels start to
increase.
Arabidopsis tem1 mutants over-expressing AmTEM, OeTEM or AtTEM1 exhibited delayed
flowering compared to the tem1 mutant, which demonstrated their role in regulating flowering
time. Over-expression of AmTEM was shown to increase the length of the juvenile phase, delay
the induction of AtCO and AtFT expression and reduce the overall levels of AtFT expression.
Conversely, the juvenile phases of tem1 single and tem1/2 double mutants were shown to be
shorter than in wild-type plants, with the induction of AtCO and AtFT expression occurring
earlier.
These findings are consistent with a role for TEM in regulating juvenility, which occurs
through the down-regulation of FT and CO, and results in the inability to proceed to reproductive
growth.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QK Botany | ||||
Library of Congress Subject Headings (LCSH): | Garden snapdragon -- Physiology, Olive -- Physiology, Plants, Flowering of, Plant photoperiodism | ||||
Official Date: | May 2012 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | School of Life Sciences | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Thomas, Brian, 1949- ; Massiah, Andrea Juliet | ||||
Sponsors: | University of Warwick | ||||
Extent: | xvi, 200 leaves : ill., charts | ||||
Language: | eng |
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