Isolation And Functional Analysis Of Stress-response Genes TaABC1 And TaSAP1/2 From Wheat (Triticum Aestivum L.)

Wheat (Triticum eastivum L.) is one of the most important food crops in the world. Abiotic stresses such as drought, salinity, and low temperature drastically impact on wheat growth and productivity. Improvement of wheat stress-resistance and cultivation of new varieties are one of the most economic and effective measures to respond the environmental problem. Therefore, it is a greatly important premise and basis to uncover the stress-resistant mechanism and discover resistant genes in wheat for accomplishing goals. To further understand wheat stress-resistant molecular mechanism and utilize stress-resistant genes, wheat ABC1 protein kinase gene TaABC1 (Triticum aestivum activity of bc1 complex) and A20/AN1 zinc-finger genes TaSAP1 and TaSAP2 (Triticum aestivum stress-associated protein 1 and 2) were isolated based on a cDNA library of wheat (cultivar Hanxuan 10) seedlings responding to drought-stress constructed by suppression subtractive hybridization method. We intensively study the functions of target genes in abiotic stress response. Our results are mainly as follows:1. TaABC1 protein kinase was localized to the cell membrane, cytoplasm, and nucleus. TaABC1 was expressed in the leaves and roots at stages of seedling and booting, and young spikes of wheat. The effects of TaABC1 in transgenic tobacco and Arabidopsis plants on responses to drought, salt, and cold stress were further investigated. Transgenic plants overexpressing TaABC1 gene showed higher osmotic adjustment ability, cell membrane stability, water retention capacity and photochemistry efficiency, and controlled reactive oxygen species homeostasis, and longer leaf stay-green. In addition, stress-responsive genes, such as DREB1A, DREB2A, RD29A, ABF3, KIN1, CBF1, LEA, and P5CS, were up-regulated in the transgenic plants detected by real-time quantitative PCR. The results suggest that TaABC1 overexpression enhances drought, salt and cold stress tolerance in Arabidopsis.2. TaSAP1 and TaSAP2 are A20/AN1 zinc-finger protein genes from wheat. They were localized to the cytoplasm. Both TaSAP1 and TaSAP2 were induced by PEG, high salt, cold and exogenous ABA treatments, and found at different development stages and different tissues of wheat. Under PEG and NaCl treatments, the expression pattern of TaSAP1 was similar to that of TaSAP2, but the expression intensity of TaSAP1 was higher than TaSAP2. Under cold stress condition, the expression of TaSAP1 was down-regulated, but the expression of TaSAP2 was up-regulated. Under ABA treatment, both TaSAP1 and TaSAP2 were up-regulated, but the expression levels were low. This suggests that TaSAP1 and TaSAP2 may be involved in the response to stress in wheat.3. The effects of TaSAP1 and TaSAP2 in transgenic Arabidopsis plants on responses to drought, salt, and cold stress were further investigated. Transgenic plants overexpressing TaSAP1 showed higher germination rate, longer root, higher leaf water retention, photochemistry efficiency, leaf stay-green and survival rate, cell membrane stability were maintained. Transgenic plants exhibited the stronger tolerance to drought, salinity and osmotic stress compared to the control plants. Overexpressing TaSAP2 transgenic plants also showed longer root, higher leaf water retention, photochemistry efficiency, leaf stay-green, cell membrane stability and survival rate. And they represent stronger tolerance to drought and cold stress compared to the control plants. These results suggest that TaSAP1 and TaSAP2 overexpression enhances drought, salt or cold stress tolerance in Arabidopsis.4. In addition, the expression of stress-responsive genes, such as DREB1B, DREB2A, RD29A, RD29B and ABF3, were up-regulated in the transgenic plants detected by real-time quantitative PCR analysis. However, the expression levels of ABF4, ICE1 and Cor15 did not show significantly different between wild-type plants and transgenic plants. The results implied that TaSAP1 and TaSAP2 may play an important role in the regulated network responding to environment stresses in plants.5. The mutant of AtSAP2, which was highly similar to TaSAP1 and TaSAP2, showed more sensitive to drought and lower recovery ability after rewatering compared to wild-type and transgenic plants. The results suggested that TaABC1, TaSAP1 and TaSAP2 enhanced the tolerance to drought, salt, and cold stress in Arabidopsis, and implied that they may act as the regulatory factors involved in the multiple stress response pathways.