Full text
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| Author(s): |
Kelly Seligman
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia |
| Defense date: | 2008-02-21 |
| Examining board members: |
Ione Salgado;
Helenice Mercier;
Eliana Regina Forni Martins
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| Advisor: | Cecilia Alzira Pinto Maglio; Ione Salgado |
| Abstract | |
The radical nitric oxide (NO), that can be produced in the organism by arginine oxidation or nitrite reduction, is an important signaling molecule in plants acting as modulator of several metabolic and developmental processes. Recently NO was identified as one of several signals involved in flowering. The transition from vegetative to reproductive growth is delayed in mutant plants that overproduce NO, while this process is precocious in mutant plants deficient in NO synthesis. The main objective of this study was to identify the sites of NO production during floral development of Arabidopsis thaliana. The fluorescent probes, 4,5-daminofluorescein diacetate and 1,2-diaminoanthraquinone, were utilized to localize in situ, by fluorescence microsopy, the NO production in floral buds of A. thaliana at different stages of development. Still, NO production by the floral structures was compared between wild-type and double defective mutant plants for structural genes of nitrate reductase enzyme - NR - (nia1 nia2) which have reduced content of amino acids and nitrite and, consequently, of NO in their leaves. It was also analyzed the effect of the NO scavenger, CPTIO, in preventing the fluorescence emission. The results showed that NO is synthesized in specific cells and tissues in the floral structure and its production increases with the floral development until anthesis: the fluorescence of the indicators, prevented by NO scavenger, was restricted to the stigmatic papillae, in the gynoecium, and to pollen grains produced by anther in stamen. Mutant plants of A. thaliana nia1 nia2 showed the same pattern of NO emission by the floral organs to that observed in the wild type genotype. Sepals and petals showed no significant NO production in both genotypes analyzed. Validation of the results obtained by fluorescence microscopy was realized by incubating floral tissues with DAF-2 and quantifying, by spectrofluorimetry, the DAF-2T resulted from reaction between the probe and the NO emitted by the tissues. Data obtained by spectrofluorimetry showed that the fluorescence intensity emitted by floral buds was higher during stage 11 of development, corroborating localization data obtained by fluorescence microscopy. Additionally, wild type plants showed greater intensity of fluorescence emission, on average, than nia1 nia2 plants: 1,39 and 1,89 times higher in phases 11 and 13 of development, respectively. A second objective of this work was to evaluate the role of the NR enzyme in floral induction. Data obtained revealed that nia1 nia2 plants flowers earlier, 6 days on average, than the wild-type plants. To verify whether the early flowering phenotype in nia1 nia2 was only consequence of the NO deficiency, or was also due to the amino acids deficiency, it were analyzed the parameters of floral induction in nia1 nia2 plants treated with the amino acids arginine or glutamine for the recovery of the amino acids levels. Flowering in this mutant remained precocious, suggesting that the early flowering phenotype is a consequence of NO deficiency in these plants during the vegetative growth. These results suggest that NO may have an important role in the flowering process and to the reproductive success of the plant (AU) | |