RESUMO
Peroxidases (PODs) are enzymes that play important roles in catalyzing the reduction of H2O2 and the oxidation of various substrates. They function in many different and important biological processes, such as defense mechanisms, immune responses, and pathogeny. The POD genes have been cloned and identified in many plants, but their function in alfalfa (Medicago sativa L.) is not known, to date. Based on the POD gene sequence (GenBank accession No. L36157.1), we cloned the POD gene in alfalfa, which was named MsPOD. MsPOD expression increased with increasing H2O2. The gene was expressed in all of the tissues, including the roots, stems, leaves, and flowers, particularly in stems and leaves under light/dark conditions. A subcellular analysis showed that MsPOD was localized outside the cells. Transgenic Arabidopsis with MsPOD exhibited increased resistance to H2O2 and NaCl. Moreover, POD activity in the transgenic plants was significantly higher than that in wild-type Arabidopsis. These results show that MsPOD plays an important role in resistance to H2O2 and NaCl.
Assuntos
Arabidopsis/genética , Medicago sativa/genética , Peroxidase/genética , Plantas Geneticamente Modificadas/genética , Arabidopsis/efeitos dos fármacos , Arabidopsis/crescimento & desenvolvimento , Flores/enzimologia , Flores/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Peróxido de Hidrogênio/toxicidade , Medicago sativa/enzimologia , Medicago sativa/crescimento & desenvolvimento , Estresse Oxidativo/genética , Plantas Geneticamente Modificadas/efeitos dos fármacos , Plantas Geneticamente Modificadas/crescimento & desenvolvimento , Tolerância ao Sal/genética , Cloreto de Sódio/toxicidade , Estresse Fisiológico/genéticaRESUMO
The stay-green gene (SGR) is a key regulatory factor for chlorophyll degradation and senescence. However, to date, little is known about SGR in Zoysia japonica. In this study, ZjSGR was cloned, using rapid amplification of cDNA ends-polymerase chain reaction (PCR). The target sequence is 831 bp in length, corresponding to 276 amino acids. Protein BLAST results showed that ZjSGR belongs to the stay-green superfamily. A phylogenetic analysis implied that ZjSGR is most closely related to ZmSGR1. The subcellular localization of ZjSGR was investigated, using an Agrobacterium-mediated transient expression assay in Nicotiana benthamiana. Our results demonstrated that ZjSGR protein is localized in the chloroplasts. Quantitative real time PCR was carried out to investigate the expression characteristics of ZjSGR. The expression level of ZjSGR was found to be highest in leaves, and could be strongly induced by natural senescence, darkness, abscisic acid (ABA), and methyl jasmonate treatment. Moreover, an in vivo function analysis indicated that transient overexpression of ZjSGR could accelerate chlorophyll degradation, up-regulate the expression of SAG113, and activate ABA biosynthesis. Taken together, these results provide evidence that ZjSGR could play an important regulatory role in leaf chlorophyll degradation and senescence in plants at the molecular level.