| Rice is an important crop for more than half of the world’s population, and its research would have great value in application. As a sessile organism, rice is easily threatened by external abiotic stress in the whole growth stage. Abiotic stresses affect rice growth and resulting in serious influence on rice yield and quality performance. Therefore, it’s very important to find the key regulatory or functional genes responsive to abiotic stresses, to reveal the molecular mechanisms of stress tolerance and to improve rice resistance by genetic engineering techniques.Heat shock transcription factors (Hsfs) can regulate heat shock protein which involved in the center process of the stress response and play an important role in signaling transduction and heat resistance. bZIP is one of the largest transcription factors family, which involved in various biological process and have great impact on plant growth. To investigate the function of OsHsfB2b and OsbZIP74genes, over-expression vector and RNAi vector of OsHsfB2b and OsbZIP74were constructed. Transgenic rice plants were obtained via Agrobacterium-mediated transformation and confirmed at transcriptional level. The stress-tolerance of OsHsfB2b transgenic rice plants were analyzed when they were exposed to different abiotic stresses including salt stress, drought stress, high temperature and low temperature treatment. The main results are as following:1. OsHsfB2b transgenic rice plants were confirmed at transcriptional level. The comparison of agronomic characters revealed that OsHsfB2b-OE transgenic plants were shorter than the control plants. The main difference was the length of the second internode.2. When germinated under different concentrations of mannitol and NaCl, the seed germination percentage and shoot length of both transgenic and wild type rice was decreased with the increasing mannitol and NaCl concentrations. However, the seed germination percentage and shoot length of OsHsfB2b-OE transgenic rice was lower than that of wild-type seeds. Overexpression of OsHsfB2b decreased the tolerance of rice seeds to drought and high salt stresses during germination.3. The results of drought stress treatment showed that OsHsfB2b-OE transgenic plants exhibited more damage symptoms and the survival rate is lower than wild-type plants. After treatments, the ion leakage and MDA content increased more significantly in transgenic plants than in wild-type plants. In contrast, the proline content increased more significantly in wild-type plants than in transgenic plants. These results suggest that OsHsfB2b may be a negative regulator in drought stress.4. After high temperature stress treatments, the transgenic plants and wild-type showed no obvious phenotypic differences in seeding stage. However, at the flowering stage, pollen fertility, seed setting rate and proline content of OsHsfB2b-OE were higher than that of the wild-type plants, while the MDA content was lower in wild-type.5. Three-week-old OsHsfB2b transgenic rice plants were exposed to5℃for5days. After two weeks of recovery, none of the wild-type and OsHsfB2b-RNAi plants survived, whereas13%of OsHsfB2b-OE plants survived. This result suggests that the over-expression of OsHsfB2b enhanced cold stress tolerance in transgenic rice plants.6. Three-week-old OsHsfB2b transgenic rice plants were irrigated with a solution containing200mM NaCl for7days. After this treatment, the roots of OsHsfB2b-OE turned yellow and the leaves of OsHsfB2b-RNAi began wilting, whereas wild-type plants showed no visible changes, suggesting that seedling OsHsfB2b transgenic rice shows no significant effect under salt stress.7. Plant over-expression and RNAi expression vectors for OsbZIP74were constructed. Transgenic rice plants were obtained via Agrobacterium-mediated transformation and confirmed at transcriptional level. |
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