| Drought is one of major abiotic stresses which greatly affected the high and stable yields of wheat. The researches focused on the molecule mechanisms and transgenic breeding for drought tolerance of wheat is very significant to enhance the drought tolerance and water using efficiency. In this article, based on the systematic analysis of gene expression profiles of under the water-stress in wheat, five drought-stress induced genes, which encoding NAC transcription factors, were cloned and their expression patterns were characterized. Trehalose is a kind of oligose which play an important role in cellular protection under dehydration conditions and trying to accumulate proper trehalose by genetic engineering is an effective method to enhance the ability of drought tolerance in crop plants. In the previous research of our group, some transgenic wheat materials with a fusion gene TPSP (fused by the otsA and otsB gene which encodes trehalose-6-phosphate synthase and trehalose-6-phosphate phosphatase respectively) were obtained. In this article, T2 transgenic lines of the transgenic wheat were planted and identified. The major results of this article are summarized as follows:1,water-stress induced genes TaNAC12, TaNAC34, TaNAC56, TaNAC78 and TaNAC478,which encoding NAC transcriptional factors, were cloned by RT-PCR from wheat and the sequence analysis of them showed that a NAM domain,which belonged to the NAC gene family, was contained in the deduced amino acid sequences coded by the five cloned genes. The homology of TaNAC12, TaNAC34, TaNAC56, and TaNAC78 proteins was up to 96.9% between them and the genomic analysis indicated that two typical introns (94bp and 190bp in long respectively) were included in these four genes.2,The expression patterns of TaNAC12, TaNAC34, TaNAC56 and TaNAC78 under the water- and salt-stress and ABA treatment were studied. The results showed that the expression of all tested genes, except TaNAC34 which is weakly expressed, were induced with the water- and salt-stresses and ABA treatment in roots,and most of these genes were similarly induced under the different treatments in leaves compared to those in roots, while the expression of TaNAC34 was unsensitive to NaCl stress in leaves. 3,The expression patterns of TaNAC12, TaNAC34, TaNAC56 and TaNAC78 in the different tissues and developing and germinating wheat seeds were studied. The results showed that TaNAC12 was weakly expressed in the roots,stems,leaves and flag leaves, but highly expressed in the stamen and pistil (including stigma and ovary). TaNAC34 was expressed in the roots and stems, but was not detected in other tissues. TaNAC56 had a high-level expression in roots, stamens and pistils while was not detected in other tissues. TaNAC78 was strongly expressed in the roots, while weakly expressed in other tissues. During the seed development, TaNAC12 and TaNAC78 were expressed at the time point of 5 days after pollination, but were weakly expressed at the latter time pionts. The expression of TaNAC56 was gradually increased during the seed development. In germinating seeds, TaNAC56 was highly expressed at the time point of 48 h after water addition in the embryo and the expression of. TaNAC78 was changed in this process, while The expression of TaNACs.were not detected in the endosperm.4,A prokaryotic expression vector for TaNAC478 was constructed and successfully expressed in vitro which provided a foundation for further study on the interaction between NAC transcription factors and NAC cis-acting elements.5,Based on the obtained transgenic wheat lines, the identification of transgene were performed and its expression was detected in the transgenic lines. The drought tolerance of the transgenic wheat lines were primarily assayed and several transgenic lines with violent drought tolerance were identified. These results will provide a foundation for further breeding utilization of the transgenic wheat materials for drought tolerance breeding. |
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