Analyzing Drought Tolerant Related Characteristics Of Transgenic Wheat Lines With The TPSP Gene

Drought is one of environmental stresses which affected the wheat yield greatly and improving the drought tolerance has been an important breeding objective in wheat. Trehalose is a kind of oligosaccharide which can protect dehydrate cells significantly. Naturely, some plants can tolerant severe drought mainly due to the induciable accumulation of a large number of trehalose in its cells under the stress. Thus, try to improve the ability of trehalose synthesis has become one of the important reseach directons for drought tolerant breeding. In our previous research work, the TPSP gene coding for a fusion protein of trehalose 6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP) was cloned and constructed, and transgenic wheat with TPSP gene was also obtained. In this study, the transgene was tracked by PCR analysis in the T3 generation of transgenic population and 20 homozygous transgenic lines were identified, and the drought tolerant related characteristics of these lines were systemeticly anaylyzed which provide important basis for the further utilization of transgenic materials in drought resistant breeding in wheat.. The main research contents of this study were summarized as follows:1.A cDNA of trehalose 6-phosphate synthase in wheat (TPS1) was cloned by RT-PCR and the sequencing analysis showed that it can encode a protein which is highly homologous to the Arabidopsis TPS.2. Under the mimic drought conditions, the drought tolerance assay of T4 transgenic lines showed that there were significant differences of withering symptom between transgenic lines and no-transgenic control at the time point of 48h after stress, and transgenic lines were abviously tolerant to the drought conditions. Both of the transgenic and control leaves were severely withered, and the roots were shrunk and become brown at the time point of 100h after stress. The percentage of yellow leaves were calculated at the time point of 24h after rewatering and the results showed that the yellow leaf ratios of transgenic line 4-9-1, 4-4-4 and 30-1-2 were 25.2%, 23.3 and 27.6%, which were significantly lower than the ratio (48.8%) of no-transgenic control. Comparative analysis on proline content in wheat leaves showed an "S" curve increasing pattern during the drought stress,and the accumulating speed and volume of praline in 3 transgenic lines were significantly higher than that in no-transgenic control. The detection of chlorophyll fluorescence parameters showed that the Fv/Fm values of 3 transgenic lines were slightly higher than that of no-transgenic control under the drought stress, while the Fv/Fo values of transgenic line 4-4-4 were significantly higher than that of control, which indicated that the photosynthetic efficiency of photosystem II in transgenic lines were enhanced under drought stress. The drought tolerance assay using an artificial water-stress system indicated that almost all of no-transgenic leaves were severely withered at the time point of 100h after stress treatment, while the transgenic lines presented stronger drought tolerance. The percentage of yellow leaves were calculated at the time point of 24h after rewatering and the results showed that the yellow leaf ratios of transgenic line 4-9-1, 4-4-4 and 30-1-2 were 25.2%, 23.3 and 27.6%, which were significantly lower than the ratio (48.8%) of no-transgenic control.3 Drought resistance of transgenic lines were identified Under the natural drought conditions. Determination of the soil moisture,the relative water content and the fluorescence in the period of flowering stage, mid-filling stage and later grain filling stage, results showed that: the leaf water contents of 10 lines were significantly higher than the control , and Fv / Fo and Fv / Fm of 6 lines were better than the control among the 20 transgenic lines.4 Analysis of the agronomic traits of the transgenic Lines,the results showed that: transgenic lines had different degrees of differences,including the plant height, the tiller number ,the total spikes,the grain number of main stem,the tiller grain number,the main spike length,the tiller spike length, the grain weight and the yield, Etc. The height of each strain did not change significantly. Significant differences were observed in grain weight of HT4-7 and HT4-8, and the grain length increased by 1.23 times comparing with the control. The total spike number of HT4-5 increased by 13.8% comparing with the control。Theoretical yields increased significantly,which indicates that agronomic traits of the transgenic plants were altered and parts of the shape were improved.