RESUMO
Manganese (Mn) is an essential micronutrient for plants, but is toxic when present in excess. The rice plant (Oryza sativa L.) accumulates high concentrations of Mn in the aerial parts; however, the molecular basis for Mn tolerance is poorly understood. In the present study, genes encoding Mn tolerance were screened for by expressing cDNAs of genes from rice shoots in Saccharomyces cerevisiae. A gene encoding a cation diffusion facilitator (CDF) family member, OsMTP8.1, was isolated, and its expression was found to enhance Mn accumulation and tolerance in S. cerevisiae. In plants, OsMTP8.1 and its transcript were mainly detected in shoots. High or low supply of Mn moderately induced an increase or decrease in the accumulation of OsMTP8.1, respectively. OsMTP8.1 was detected in all cells of leaf blades through immunohistochemistry. OsMTP8.1 fused to green fluorescent protein was localized to the tonoplast. Disruption of OsMTP8.1 resulted in decreased chlorophyll levels, growth inhibition in the presence of high concentrations of Mn, and decreased accumulation of Mn in shoots and roots. However, there was no difference in the accumulation of other metals, including Zn, Cu, Fe, Mg, Ca, and K. These results suggest that OsMTP8.1 is an Mn-specific transporter that sequesters Mn into vacuoles in rice and is required for Mn tolerance in shoots.
Assuntos
Adaptação Fisiológica/efeitos dos fármacos , Manganês/toxicidade , Oryza/fisiologia , Proteínas de Plantas/metabolismo , Sequência de Aminoácidos , Cátions , DNA Complementar/genética , DNA Complementar/isolamento & purificação , Difusão , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Técnicas de Silenciamento de Genes , Dados de Sequência Molecular , Mutação/genética , Oryza/efeitos dos fármacos , Oryza/genética , Fenótipo , Proteínas de Plantas/química , Proteínas de Plantas/genética , Transporte Proteico/efeitos dos fármacos , Saccharomyces cerevisiae/efeitos dos fármacos , Análise de Sequência de Proteína , Frações Subcelulares/efeitos dos fármacos , Frações Subcelulares/metabolismoRESUMO
The short-term responses of H(2)O(2)-depletion-related parameters in moss Hypnum plumaeforme to the combined stress induced by Pb and Ni were investigated. The results showed that the Pb and Ni stress induced dose-dependent accumulation of hydrogen peroxide (H(2)O(2)). The increase of peroxidase (POD) activity and decrease of ascorbate peroxidase (APX) activity were observed under the combined heavy metal application. The antioxidants, ascorbate (AsA) and proline content, increased significantly when the metals were applied together. The study indicated that the cell damage caused by Pb stress was higher than that caused by Ni stress, Pb and Ni had synergistic effect in inducing the oxidative stress in moss H. plumaeforme, especially under the combination of high concentration of Ni (0.1 and 1.0 mM) and Pb. Content of proline, H(2)O(2) and the activity of POD, all showed a dose-dependent increase under Pb and Ni stress, suggesting their practical value as biomarkers in moss biomonitoring, especially in the case of light pollution caused by heavy metals without the changes in the appearance of mosses.