No description available.

No description available.

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.

No description available.

All the tissues within the developing embryo are comprised of cells formed from one of the three germ layers defined during gastrulation; the ectoderm, mesoderm and endoderm. Understanding how the germ layers are formed and subsequently differentiate into different tissues is the basis of developmental biology.

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.

The aim of this research was to study the effects of Salinity & Heavy Metals on the Sporophyte & Gametophyte generations of Arabidopsis thaliana. After developing a pollen germinating protocol, some basic experiments were conducted to determine the effects on chemical & physical parameters on pollen germination & pollen tube growth. Additions of heavy metals & high concentrations of buffer (Tris-HCI) in pollen germinating medium (PGM), inhibited pollen germination (PG) & pollen tube length (PTL), while pH range (7.0-9.0) had little effect. The idea of 2-fold effect (nutritional & osmotic) of sucrose was supported in results. In vivo pollen growth was much greater than in vitro & genotypic differences occurred among the mutants for PG & PTL. Comparing the pollen nutritional requirements for PG & PTL between Cicer arietinum & A. thaliana, it was noted that the pollen of the former had a greater requirement for H(_3)BO(_3) & Ca(N0(_3))(_2) than latter. The range of temperatures (0 C-35 C) studied, indicated that the most favourable temperature for PG was 20 C & for PTL 25 C , while extreme temperatures (0 C, 35 C) were harmful to A. thaliana pollen. 20 C was found to be optimum temperature for PG & PTL of C. arietinum. Correlation between pollen tube growth rates (PTGRs) and sporophytic traits of Fls showed a generally strong positive correlation with most of sporophytic traits, but a very loose to negative correlation for earliness parameters. Recording the impacts of salinity, parallel effects were found for the sporophytic & gametophytic generations of the plant, as reported by earlier workers. The results also indicated that it is possible to develop a pollen plant salinity index (PPSI) for plant species under specific plant growing conditions. It was also observed that salinity stress during pollen gametogenesis preconditioned pollen to high salinity levels, resulting in higher PG & PTL than in pollen raised under non-saline conditions. Similarly, the fruit-setting, seed-setting & seed-filling were relatively less affected by saline-stress, in progeny when pollen and pistilate plants were grown under similar saline regimes. Anatomical studies showed that salinity induced changes in the epidermis, cortex, pericycle, xylem, pith & cross sectional diameter of vascular bundle (CSDVB) in stem, leaf & root tissues. Lower reductions for the fruit-setting, seed-setting & seed-filling were recorded in response to the high heavy metal concentrations in progeny when pollen and pistilate plants were raised under similar heavy metal regimes. It was apparent that pollen become conditioned to a stress environment during its development in the anthers of stressed plants, & this preconditioning allowed its pollen tubes to grow more successfully in the styles of the female parents growing in a similarly stressed environment, where the pistil may have accumulated higher levels of heavy metals. Heavy metals induced changes in stem shape, epidermis, cortex, vascular bundles & chloroplasts in stems. The metals induced changes in the leaf thickness, epidermis, palisade cell size, spongy mesophyll area, size of intercellular spaces & chloroplasts in the leaf, causing disruption of cortical layers, lignification of pericycle & phloem, damage to the endodermis and increase in xylem cell size & stele diameter in roots.

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xxi, 230 leaves + photos, tables, graphs ; 30 cm / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1979) from the Dept. of Soil Science, University of Adelaide