RESUMO
Ascorbate (AsA) is very important in scavenging reactive oxygen species in plants. AsA can reduce photoinhibition by xanthophyll cycle to dissipate excess excitation energy. GGP is an important enzyme in AsA biosynthesis pathway in higher plants. In this study, we cloned a gene, SlGGP-LIKE, that has the same function but different sequence compared with SlGGP. The function of SlGGP-LIKE gene in response to oxidative stress was investigated using transgenic tobacco plants overexpressed SlGGP-LIKE under methyl viologen treatment. After oxidative stress treatment, transgenic tobacco lines exhibited higher levels of reduced AsA content and APX activity than WT plants. Under oxidative stress, transgenic tobacco plants accumulated less ROS and exhibited lower degrees of REC and MDA. Consequently, relatively higher levels of Pn, Fv/Fm, de-epoxidation status of xanthophyll cycle and D1 protein were maintained in transgenic tobacco plants. Hence, overexpression of SlGGP-LIKE gene enhances AsA biosynthesis and can alleviate the photoinhibition of PSII under oxidative stress.
Assuntos
Adaptação Fisiológica/genética , Genes de Plantas , Nicotiana/fisiologia , Estresse Oxidativo/efeitos dos fármacos , Paraquat/toxicidade , Solanum lycopersicum/genética , Sequência de Aminoácidos , Ascorbato Peroxidases/metabolismo , Ácido Ascórbico/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Peróxido de Hidrogênio/metabolismo , Luz , Malondialdeído/metabolismo , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Transporte Proteico/efeitos dos fármacos , Alinhamento de Sequência , Frações Subcelulares/metabolismo , Superóxidos/metabolismo , Nicotiana/efeitos dos fármacos , Nicotiana/genética , Nicotiana/efeitos da radiação , Xantofilas/metabolismo , Zeaxantinas/metabolismoRESUMO
The NAC proteins are the largest transcription factors in plants. The functions of NACs are various and we focus on their roles in response to abiotic stress here. In our study, a typical NAC gene (SlNAM1) is isolated from tomato and its product is located in the nucleus. It also has a transcriptional activity region situated in C-terminal. The expression levels of SlNAM1 in tomato were induced by 4°C, PEG, NaCl, abscisic acid (ABA) and methyl jasmonate (MeJA) treatments. The function of SlNAM1 in response to chilling stress has been investigated. SlNAM1 overexpression in tobacco exhibited higher germination rates, minor wilting, and higher photosynthetic rates (Pn) under chilling stress. Meanwhile, overexpression of SlNAM1 improved the osmolytes contents and reduced the H2O2 and O2â¢- contents under low temperature, which contribute to alleviating the oxidative damage of cell membrane after chilling stress. Moreover, the transcripts of NtDREB1, NtP5CS, and NtERD10s were higher in transgenic tobacco, and those increased expressions may confer higher chilling tolerance of transgenic plants. These results indicated that overexpression of SlNAM1 could improve chilling stress tolerance of transgenic tobacco.