RESUMEN
We investigated the mechanism of selenium (Se) tolerance using an Arabidopsis thaliana knockout mutant of a sulfate transporter, sultr1;2. Se stress inhibited plant growth, decreased chlorophyll contents, and increased protein oxidation and lipid peroxidation in the wild type, whereas the sultr1;2 mutation mitigated damage of these forms, indicating that sultr1;2 is more tolerant of Se than the wild type is. The accumulation of symplastic Se was suppressed in sultr1;2 as compared to the wild type, and the chemical speciation of Se in the mutant was different from that in the wild type. Regardless of Se stress, the activities of ascorbate peroxidase, catalase, and peroxidase in the mutant were higher than in the wild type, while the activity of superoxide dismutase in the mutant was the same as in the wild type. These results suggest that the sultr1;2 mutation confers Se tolerance on Arabidopsis by decreasing symplastic Se and maintaining antioxidant enzyme activities.
Asunto(s)
Proteínas de Transporte de Anión/genética , Proteínas de Arabidopsis/genética , Arabidopsis/genética , Raíces de Plantas/genética , Tolerancia a la Sal/genética , Compuestos de Selenio/farmacología , Selenio/farmacología , Adaptación Fisiológica/genética , Proteínas de Transporte de Anión/deficiencia , Antioxidantes/metabolismo , Arabidopsis/efectos de los fármacos , Arabidopsis/metabolismo , Ascorbato Peroxidasas/metabolismo , Catalasa/metabolismo , Técnicas de Inactivación de Genes , Peroxidación de Lípido/efectos de los fármacos , Peroxidación de Lípido/genética , Mutación , Estrés Oxidativo/efectos de los fármacos , Estrés Oxidativo/genética , Peroxidasas/metabolismo , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/metabolismo , Plantas Modificadas Genéticamente/efectos de los fármacos , Plantas Modificadas Genéticamente/metabolismo , Ácido Selénico , Selenio/metabolismo , Compuestos de Selenio/metabolismo , Estrés Fisiológico/genética , Superóxido Dismutasa/metabolismoRESUMEN
In the present study, papaya (Carica papaya) seed and edible pulp were carefully separated and then the contents of benzyl isothiocyanate and the corresponding glucosinolate (benzyl glucosinolate, glucotropaeolin) quantified in each part. The papaya seed with myrosinase inactivation contained >1 mmol of benzyl glucosinolate in 100 g of fresh seed. This content is equivalent to that of Karami daikon (the hottest Japanese white radish) or that of cress. The papaya seed extract also showed a very high activity of myrosinase and, without myrosinase inactivation, produced 460 micromol of benzyl isothiocyanate in 100 g of seed. In contrast, papaya pulp contained an undetectable amount of benzyl glucosinolate and showed no significant myrosinase activity. The n-hexane extract of the papaya seed homogenate was highly effective in inhibiting superoxide generation and apoptosis induction in HL-60 cells, the activities of which are comparable to those of authentic benzyl isothiocyanate.