No description available.

No description available.

No description available.

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.

No description available.

The RNA binding protein Flowering Time Control Locus A (FCA) regulates flowering in rice and Arabidopsis. The abscisic acid binding protein ABAP1 shares high sequence homology to FCA and was considered the FCA homologue in barley. The current study investigates the existence of ABAP1 as an independent gene product and also the cloning, characterization and functional significance of the gamma (γ) isoform of FCA from barley. Barley FCA protein showed higher sequence similarity to wheat and rice FCA compared to Arabidopsis FCA. It contains two RNA recognition motifs (RRMs), a glycine rich region at the N-terminal end, the WW domain and a poly-glutamine region immediately downstream of WW domain at the C-terminal. In developing barley embryos, FCA transcripts could be detected from 2 days after pollination (DAP) up to late maturity without any detectable change within these stages. FCA transcript levels declined as germination progressed in barley embryos and the FCA transcripts were retained for longer duration when germination was reduced with application of ABA. FCA also showed up-regulation by ABA and abiotic stresses in barley germinating seeds and seedlings. Transient co-expression of barley FCA or a truncated FCA (lacking RRM) with a maize VP1 promoter-GUS construct or a wheat Em gene promoter-GUS construct in barley aleurone layer protoplasts led to increased GUS activity in both cases. Adding ABA during the incubation enhanced the observed increase due to FCA expression. Similar effects of transient over-expression of FCA in barley embryos affected VP1. Barley FCA localized to the nucleus. This nuclear localization was due to the nuclear localization signal within the protein and not due to the RNA recognition motifs (RRMs) as the truncated FCA lacking RRMs also localized to the nucleus. Barley FCA did not restore the flowering phenotype in an Arabidopsis fca-1 mutant. In conclusion, I have shown that barley FCA is up-regulated by ABA and stress in embryos and affects ABA signalling in barley caryopses. The properties of FCA appear to have diverged between dicot and monocot systems.

Abstract cannot be copied from pdf document. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1987.

The RNA binding protein Flowering Time Control Locus A (FCA) regulates flowering in rice and Arabidopsis. The abscisic acid binding protein ABAP1 shares high sequence homology to FCA and was considered the FCA homologue in barley. The current study investigates the existence of ABAP1 as an independent gene product and also the cloning, characterization and functional significance of the gamma (γ) isoform of FCA from barley. Barley FCA protein showed higher sequence similarity to wheat and rice FCA compared to Arabidopsis FCA. It contains two RNA recognition motifs (RRMs), a glycine rich region at the N-terminal end, the WW domain and a poly-glutamine region immediately downstream of WW domain at the C-terminal. In developing barley embryos, FCA transcripts could be detected from 2 days after pollination (DAP) up to late maturity without any detectable change within these stages. FCA transcript levels declined as germination progressed in barley embryos and the FCA transcripts were retained for longer duration when germination was reduced with application of ABA. FCA also showed up-regulation by ABA and abiotic stresses in barley germinating seeds and seedlings. Transient co-expression of barley FCA or a truncated FCA (lacking RRM) with a maize VP1 promoter-GUS construct or a wheat Em gene promoter-GUS construct in barley aleurone layer protoplasts led to increased GUS activity in both cases. Adding ABA during the incubation enhanced the observed increase due to FCA expression. Similar effects of transient over-expression of FCA in barley embryos affected VP1. Barley FCA localized to the nucleus. This nuclear localization was due to the nuclear localization signal within the protein and not due to the RNA recognition motifs (RRMs) as the truncated FCA lacking RRMs also localized to the nucleus. Barley FCA did not restore the flowering phenotype in an Arabidopsis fca-1 mutant. In conclusion, I have shown that barley FCA is up-regulated by ABA and stress in embryos and affects ABA signalling in barley caryopses. The properties of FCA appear to have diverged between dicot and monocot systems.

Typescript. / Bibliography: leaves [94]-98. / [vi], 98 l graphs, tables

vii, 285 leaves : ill., photos., tables ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Physiology, 1971