dc.contributor.advisor |
Assoc. Prof Jo Putterill |
en |
dc.contributor.advisor |
Dr Igor Kardailsky |
en |
dc.contributor.author |
Gagic, Milan, 1971- |
en |
dc.date.accessioned |
2008-03-18T23:08:46Z |
en |
dc.date.available |
2008-03-18T23:08:46Z |
en |
dc.date.issued |
2007 |
en |
dc.identifier.citation |
Thesis (PhD--Biological Sciences)--University of Auckland, 2007. |
en |
dc.identifier.uri |
http://hdl.handle.net/2292/2424 |
en |
dc.description.abstract |
Grasslands account for almost one quarter of the world’s cover of vegetation. Almost three
quarter of the world’s milk, beef and veal are produced from temperate grasslands. In New
Zealand, ryegrass (Lolium perenne) is the main pasture constituent with more than half of the
total export revenue coming from grass-related products. Much of ryegrass production and
quality depends on the timing of flowering through seasonal progression. In many plants, day
length is the critical environmental parameter that controls when plants begin to flower. In
Arabidopsis the CONSTANS (CO) gene mediates day length response. Upstream of CO is the
GIGANTEA (GI) gene which is associated with the circadian clock mechanism and is required
to promote CO expression. The FT gene is the immediate downstream genetic target of CO
and is a direct promoter of flowering.
In this study, cDNA libraries, sequence alignment and genome walking were used to sequence
and describe three putative orthologues from the ryegrass photoperiod pathway: LpGI,
LpCOL1, and LpFT3. All three behaved in a true photoperiod manner characterised by
cycling expression patterns under continuous light conditions and differential expression
patterns in LD and SD conditions. Different photoperiods brought about differences in
expression of these genes measured either by the phase shift change (LpGI and LpCOL1) or
by the change of the transcript level (LpFT3). Gene expression changes over a vernalisaton
time course were also analysed and results indicated that LpFT3 acts as the flowering
integrator. The role of LpGI, LpCOL1, and LpFT3 as putative photoperiod genes was further
confirmed by genetic mapping, which placed them on linkage groups 3, 6, and 7, respectively.
The syntenic positions in rice contain major heading date quantitative trait loci. The function
of LpFT3 was examined by over-expressing the gene in Arabidopsis under control of the
cauliflower mosiac virus (CaMV) 35S promoter. Substantially higher expression of the
endogenous Arabidopsis AtFT transcript was observed in the mutated ft-1 line overexpressing
LpFT3, suggesting a positive feedback loop either directly or through upstream
intermediaries. Overexpression of the LpGI and LpFT3 genes restored rapid flowering to the
respective gi-3 and ft-1 Arabidopsis mutants while overexpression of LpCOL1 did not
accelerate flowering either in co-2 or wild type Arabidopsis plants. However, overexpression of LpCOL1 completely restored the late flowering phenotype of the gi-3 mutant indicating the
existence of another important link outside the well established hierarchy of GI-CO-FT in the
photoperiod pathway.
This study revealed that the ryegrass photoperiod pathway genes show high similarity to their
wheat, rice and Arabidopsis counterparts. Exploring ways to modulate flowering time in
ryegrass could provide major benefits to the agricultural industry by increasing forage quality,
controlling seed and pollen production, and addressing potential problems linked with climate
change. |
en |
dc.language.iso |
en |
en |
dc.publisher |
ResearchSpace@Auckland |
en |
dc.relation.ispartof |
PhD Thesis - University of Auckland |
en |
dc.relation.isreferencedby |
UoA1789537 |
en |
dc.rights |
Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. |
en |
dc.rights.uri |
https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm |
en |
dc.subject |
flowering |
en |
dc.subject |
ryegrass |
en |
dc.subject |
photoperiod |
en |
dc.subject |
molecular |
en |
dc.title |
Flowering in ryegrass and conservation of the photoperiodic response |
en |
dc.type |
Thesis |
en |
thesis.degree.discipline |
Biological Sciences |
en |
thesis.degree.grantor |
The University of Auckland |
en |
thesis.degree.level |
Doctoral |
en |
thesis.degree.name |
PhD |
en |
dc.rights.holder |
Copyright: The author |
en |
pubs.local.anzsrc |
06 - Biological Sciences |
en |
pubs.org-id |
Faculty of Science |
en |
dc.identifier.wikidata |
Q112870150 |
|