Preliminary Functional Characterization Of OsHsp74.8 And Overexpression Vector Construction For Two MYB Genes

Rice is one of the most important crops in China. Keeping steady rice production is crucial for national food security. In recent years, climate disasters occurred frequently and resulted in serious influence on growth and yield of rice. Cloning of key regulatory or functional genes responsive to abiotic stresses and clarification of the molecular mechanisms of stress tolerance would be useful in improving rice stress resistance through genetic engineering techniques.Heat shock proteins (Hsps) are important proteins whose expression is increased when the cells are exposed to elevated temperatures or other stresses like drought and high salinity. Hsp90s is one subfamily of the Hsp gene family. There are many kinds of transcription factors in plants that play important roles in plant growth and responses to stresses. MYB family genes are important genes associated with abiotic stresses. In this study, OsHsp74.8-overexpression rice plants were exposed to different abiotic stresses including salt stress, drought stress and high temperature to the responses to stress-tolerance. Over-expression vectors of OsMyb51.6 and OsMyb41.6 genes were constructed successfully. The main results are as following:1. OsHsp74.8-OE transgenic rice plants were obtained via Agrobacterium-mediated transformation and the transformation was confirmed at transcriptional level. The results of drought stress treatments during germination showed that OsHsp74.8-OE seeds have better growth than wild-type with longer roots and seedling and higher germination rate. The results of high salinity stress treatments rate during germination also showed that OsHsp74.8-OE seeds have better growth than wild-type with longer roots and seedling and higher germination rate.2. OsHsp74.8-OE transgenic plants under drought stress treatments at flowering stage showed stronger drought tolerance than wild-type plants. Biochemical parameters of OsHsp74.8-OE transgenic plants under drought stress showed that the MDA contents and leaf conductivity were lower than wild-type plants, but the proline contents were significantly higher than the wild-type. Those parameters were consistent with phenotypic difference. These results indicated that the over-expression of OsHsp74.8 gene in rice increased tolerance to drought stress. Biochemical parameters of OsHsp74.8-OE transgenic plants in high temperature stress were similar to that of drought stress. It suggested that over-expression of OsHsp74.8 gene may also improve tolerance to high temperature stress in rice.3. Over-expression vectors of the two MYB genes OsMyb51.6 and OsMyb41.6 were constructed and confirmed by double restriction digestion identification. The over-expression vector p1301-OsMyb51.6-OE and p1301-OsMyb41.6-OE were transformed into Agrobacteria by Agrobacteria mediated rice transformation.