Cloning And Characterization Of Stress-tolerant Genes From Triticum Aestivum

High salt, drought, freezing are the major environmental factors that influence the growth of plant and account for significant reduction in the yields of crops. One of the main methods to solve this problem is to produce stress-tolerant crops. Using molecular biology, molecular genetics and genetic engineering methods to obtain the stress-tolerant crops is one of the most important aspects in modem agriculture. In this research, various wheat cultivars were used as experimental materials to study mechanism of stress tolerance of crops. The main results are as follows:1. Three novel genes in the group 3 Lea genes, named as TaLEAl, TaLEA2, TaLEA3, were cloned from wheat. TaLEAl was mainly located in cytoplasm and plasma membrane as revealed by the green fluorescent protein (GFP) fused to it. Its mRNA level was positively related to the drought tolerance of cultivars. The gene was also induced by high salt, low temperature and exogenous ABA treatments. Substantially, the expression of TaLEAs was higher in roots than that in leaves and their expression patterns were different under different stresses. Over-expression of TaLEA2 and TaLEA3 gene in yeast (Saccharomyces cerevisiae) improved growth status or survival when compared with the wild type. In addition, TaLEA2 may play an important role in osmotic stress reponse. Whereas TaLEA3 may function in sequestering ions upon stresses. Expression vectors harboring the full length or partial TaLEAl gene were constructed and transformed into Arabidopsis thaliana by vacuum infiltration method. TO seeds of transgenic plants were obtained. Analysis of stress tolerance of these transgenic plants is underway.2. A vacuole Na+/H+ antiporter gene TaNHX2 of full-length was obtained by screening the wheat cDNA library and by 5'-RACE method. The expression of TaNHX2 was specifically induced in roots and leaves by NaCl treatment. Different expression pattern of TaNHX2 was found in drought tolerant varieties and drought sensitive varieties. PEG, cold and ABA treatments also induced the expression of TaNHX2. The result implied that the expression of TaNHX2 gene was influenced by different signal transduction pathways. Overexpression of TaNHX2 gene can resume the growth status of yeast mutant (nhxl) in hygromycin medium, and recover the growth status of nhxl in NaCl medium under specific conditions. Growth status and survival rate of yeast cells were improved by over-expressing TaNHX2 gene. All the above results indicated that TaNHX2 may be a functional gene in the stress tolerance of crops..