Caracterização bioquímica de calos de espécies laticíferas em resposta ao estresse salino e análise da transcrição de osmotinas

Abstract

Calotropis procera e Cryptostegia grandiflora are laticiferous plants. It was found osmotin protein. The literature shows that the osmotinas are associated to plant defence mechanisms in situations of biotic or abiotic stress. However, there are still several inconsistencies in this hypothesis. In this context, it was used in vitro tissue culture techniques as model to assist in the understanding of how the C. procera and C. grandiflora callus cells respond to salt stress in biochemical terms, and whether the transcripts level for osmotin has raised in response to exposure to NaCl. It was added NaCl to the culture medium of Murashige e Skoog (MS) in increasing concentrations (0, 20, 40, 60 e 80 mM). The results show that callus treated with 80 mM NaCl have reduced the growth and the humidity percentage of respectively 33% and 10% in C. procera and 83% and 39% in C. grandiflora compared to the control treatment callus. Under the same conditions, it was seen an increase in ions concentrations of Na+ and Cl-, 98.9% and 98% in C. procera and 98.8% and 96% in C. grandiflora respectively. It was also seen a reduction in K+ level in callus treated with 80 mM NaCl, 43% in C. procera and 18% in C. Grandiflora, when compared to the control. The callus treated with 80 mM NaCl, showed a tendency of the proline accumulation and soluble sugars, increasing 26% and 37% in C. procera callus and 55.4% and 45% in C. grandiflora callus, respectively, when compared to control conditions. The increase in the activity of enzymes that break H2O2 has been observed in C. grandiflora callus under the salt stress, suggesting a possible oxidative damage, this increase was 73% in the ascorbate peroxidase activity and 62% in guaiacol peroxidase activity when compared to the activity of enzymes of the control callus with the treaty in 80 mM NaCl. None connection was seen between changes in the activity of the enzymes of the oxidative system and the salt stress in C. procera callus. It was evaluated the behaviour of osmotin in the osmotin transcription at 0, 2, 12, 24, 48 hours and at 4, 7, 14, 28 days of callus contact under stress. The osmotin transcripts were observed from 12 hours of contact of callus in 80mM NaCl in both species. However, it was not found osmotin by electrophoresis assays, dot blotting and mass spectrometry in the protein extracts of C. procera and C. grandiflora callus grown in control conditions and in 80 mM NaCl. Thus, the salt stress evaluation using in vitro cell model study was effective, providing cellular behaviour information for these two laticifers plants species showing their physiological, biochemical and molecular changes. The results suggest that the induced salt stress has favoured the increase of osmotin gene expression in both cases and suggests a possible relationship between osmotin of these species with the protection to salinity conditions. The failure to detect the proteins corresponding to genes provides the conception of several new hypotheses to be validated.