RESUMO
Salt tolerance of Arabidopsis knockout mutant with T-DNA insertion in ASN2 gene encoding asparagine synthetase (AS, EC 6.3.5.4) (asn2-1) was investigated. Wild-type Arabidopsis Col0 and asn2-1 mutant were grown for one month by hydroponic culture and subjected to 100 mM NaCl stress for a short time from 6 to 24 h. The salt treatment decreased chlorophyll and soluble protein contents, and increased ammonium level in the asn2-1 leaves. The salinity induced ASN1 mRNA level in the wild-type and asn2-1 leaves. By contrast, the salt treatment inhibited the transcript and protein levels of chloroplastic glutamine synthetase 2 (GS2, EC 6.3.1.2) in the wild-type and asn2-1 leaves. Increase in asparagine and proline contents in response to the salt treatment provides evidence for the role of asparagine as a prevailing stress responding amino acid. Glutamate dehydrogenase (NADH-GDH, EC 1.4.1.2) exhibited a slight increase in the α-subunit and ß-subunit in the wild-type line and the asn2-1 line, respectively under the salinity, whereas its in vitro aminating activity in the wild-type leaves was not affected. The results indicate that the asn2-1 mutant was impaired in nitrogen assimilation and translocation under salt treatment.
Assuntos
Arabidopsis/metabolismo , Asparagina/metabolismo , Aspartato-Amônia Ligase/metabolismo , Folhas de Planta/metabolismo , Proteínas de Plantas/metabolismo , Tolerância ao Sal/genética , Estresse Fisiológico/genética , Arabidopsis/genética , Aspartato-Amônia Ligase/genética , Clorofila/metabolismo , Cloroplastos/metabolismo , Glutamato Desidrogenase/metabolismo , Glutamato-Amônia Ligase/genética , Glutamato-Amônia Ligase/metabolismo , Mutagênese Insercional , Nitrogênio/metabolismo , Proteínas de Plantas/genética , Prolina/metabolismo , Subunidades Proteicas/metabolismo , Compostos de Amônio Quaternário/metabolismo , RNA Mensageiro/metabolismo , Cloreto de Sódio/farmacologia , SolubilidadeRESUMO
Tobacco (Nicotiana Tabaccum, Bureley v. Fb9) seedlings were grown for 30 days on control medium, and then treated for seven days with different concentrations (0, 10, 20, 50 and 100 muM) of CdCl(2). Cadmium (Cd) was mostly accumulated in the leaves. However, nitrate reductase and nitrite reductase activities (NR, EC 1.6.1.6 and NiR, EC 1.7.7.1) were more inhibited by Cd stress in the roots than in leaves. Glutamine synthetase activity (GS, EC 6.3.1.2) was inhibited by Cd treatment in roots and leaves. In both organs, aminating activity of glutamate dehydrogenase (GDH, EC 1.4.1.2) and protease activity were significantly stimulated in the leaves and roots of stressed plants. The lesser extents of Cd stress effects on leaves, despite their high Cd accumulation, suggest that: (i) tobacco leaves may evolve adaptive process to partially inactivate Cd ions; and (ii) tobacco is useful for phytoremediation.
