| Cassava is the third largest tuber crops and the sixth largest food crops in the world. So cassava is also an important food crops and new energy crops. During the drought period, the other crops can't survive, but cassava could still have some production for its leaves having flexible fallen mechanism. So we can speculate that cassava have an effective molecular mechanism for drought resistance. Study on drought resistance molecular mechanism of cassava, would enrich our country's gene pool of drought-resistant, and afford the theoretical guidance for the other crops drought resistance breeding.In the plant kingdom, there is HD-Zip transcription factors existed from the lower bryophyte to angiosperms. They are closely related with plant growth and development. The studies showed that plant transcription factors which responsing to drought, plays an important role in the development process. For studying the function of cassava HD-Zip transcription factors responsing to drought-resistant, the MeHDZs genes are analysised by bioinformatics technology. We analysised the MeHDZs genes expression patterns by semi-RT PCR technology. Finally, the target genes'functional verified by genetic transformation in Aranbidopsis and cassava plants. The main results were as follows:1. Using plant physiological and biochemical technology, we analysed the performance of cassava drought-tolerance. Finally, we got one cassava varieties "SC124" which have significant drought phenotype, and using it as plant material in this study.2. According to the HD-Zip genes'features of conservative structure domain, we isolated43HD-Zip-like genes in cassava genome database. The bioinformatics analysis results showed that MeHDZs genes have3typical spiral space structure. The sequence analysis of homology evolutionary relationship showed that MeHDZs genes are divided into four classes, which is the same with the other species.3. According to the cassava transcriptome data under drought stress treatment, we obtained10HD-Zip-like genes responsing drought stress. Finally, five candidate genes were selected using by semi-RT PCR results, which named MeHDZ05, MeHDS09, MeHDZ13, MeHDZ14, MeHDZ15.4. Analysis of the gene structure showed that MeHDZ05gene belongs to the ? class. Subcellular localization test showed that MeHDZ05is preferential expressed in the nucleus. MeHDZ05gene's expression is higher in petiole, and it is down-regulated by drought in petiole. On the other hand, MeHDZ05gene is lower expression level in leaf and root, but in which it can be up-regulated by drought. Over-expressed the MeHDZ05in Arabidopsis can make the root shorter than the control plants, the transgenic plants were sensitive to PEG8000and drought treatment. 5. Analysis of the gene structure showed that MeHDS09gene belongs to the ? class. Subcellular localization test showed that MeHDS09is preferential expressed in the nucleus. MeHDS09gene specifically expressed in petiole, and it is down-regulated by drought in petiole, but MeHDS09gene is up-regulated by drought in leaf tissue. MeHDS09gene is inducible expression by ABA, so it might be play a role in ABA pathway. Over-expressed the MeHDS09in Arabidopsis can make the leaf green deepen and the waxiness of leaf surface more thicken than the control, the transgenic plants were increased the tolerance ability of plants to PEG8000and drought.6. Analysis of the gene structure showed that MeHDZl3gene belongs to the ? class. Subcellular localization test showed that MeHDZ13doesn't be expressed only within the cell nucleus, and its transcription activation function is very weak in yeast experiment. So, MeHDZ13protein may not play a role in the cell nuclei. MeHDZ13gene is specifically expressed in the leaves and petioles, and up-regulated by drought treatment, wherease expression patterns was opposite in the root. Over-expressed the MeHDZ13in Arabidopsis plants can delay the seed germination, pollen number was significantly reduced and pistil stigma was smooth which make the pollen difficult accommodated, less fruit in transgenic plants, but not impacted to the leaf and plant height. The transgenic plants is sensitive to PEG and drought.7. Analysis of the gene structure showed that MeHDZ14gene belongs to the I class. Subcellular localization test showed that MeHDZ14is peculiar expressed within the cell nucleus, and has transcription activation function in yeast experiment. So, MeHDZ14protein may play a role in the cell nuclei.MeHDZ14gene is specifically expressed in the petioles, and was induction expression by drought treatment in leaves and roots, which indicated that MeHDZ14gene play an important role in early drought stage. Over-expressed the MeHDZ14in Arabidopsis can increased the ability of plants to drought tolerance, but its role less than MeHDS09.8. Analysis of the gene structure showed that MeHDZ15gene belongs to the I class. Subcellular localization test showed that MeHDZ15is peculiar expressed within the cell nucleus, and has transcription activation function in yeast experiment. So, MeHDZ15protein may play a role in the cell nuclei. MeHDZ15gene's expression level is very low in cassava plants, but it can be up-regulated by drought treatment. In the leaves tissues, MeHDZ15gene is expressed only at the late-drought stage, and it is more sensitive to drought in petiole, this implies that the MeHDZ15gene play an role in cell apoptosis process. MeHDZ15gene is inducible expression by ABA, so it might be play a role in ABA pathway. Over-expressed the MeHDZ15in Arabidopsis can increased the ability of plants to PEG8000and drought tolerance. 9. Over-expressed the MeHDZ15in Arabidopsis can make plants have more tolerance to NaCl than the control, however the MeHDZ13, MeHDZ05and MeHDS09make the plants sensitive to the NaCl.10. On the base of previous studier, we studied on transformation system of cassava suspension cells, established the Agrobacterium-mediated genetic transformation system on cassava, and successfully made the MeHDS09gene over-expressing in cassava. |
PDF Full Text Request