| In the northwest of China, water shortage is terrible, and it appeared frequently in the process of plant growth and development. In this situation, Improving the ability of water uptake is significant to promote production of crop and increase tolerance under abiotic stress.Cell pressure probe is a kind of technique which can be used directly to determinate the hydraulic properties, such as cell turgor pressure(P), volumetric elastic modulus of cells(ε), half time of water exchange(TW1/2) and hydraulic conductivity(Lp) and so on. This technique plays an important role in the study of plant root water relations.Tonoplast intrinsic protein(TIPs) is a kind of aquaporin(AQP), located on the plant vacuole membrane, and have a similar function with plasma membrane intrinsic protein(PIPs). Both of them can participate in membrane transporting of the water and some small neutral molecules. However, there is still controversial for the specific function of TIPs isoforms, and the expression regulation mechanism of tonoplast intrinsic protein remains to be explored.In this study, Plant materials including wild-type(WT) Brassica napus cv. ‘Huyou 15’, transgenic B. napus expressing Os TIP1;1, Os TIP3;1, Os TIP3;2 or p HB empty vector were cultivated by using hydroponic culture system. The cell pressure probe was employed to investigate the effects of tonoplast intrinsic protein gene(Os TIP1;1, Os TIP1;1 and Os TIP3;2) on water related parameters of primary root cortex cells among five B. napus materials under normal and water stress conditions. The water stress was simulated with PEG-6000 with Ψs –0.2 MPa.The results of this study are listed as follows:The results indicated that water stress decreased the root cortex cell turgor and the cell hydraulic conductivity, but increased the volumetric elastic modulus of cell wall and the half time of water exchange of five B. napus materials by contrast to normal condition. Under different water conditions, the cell turgor pressure of Os TIP1;1 transgenic B. napus were greater than those of Os TIP3;1 transgenic B. napus, Os TIP3;2 transgenic B. napus, p HB transgenic B. napus and WT, and there was no significant difference between other four materials.Under normal condition, the volumetric elastic modulus of cell wall and the half time of water exchange are respresented as Os TIP1;1 transgenic B. napus < Os TIP3;1 and Os TIP3;2 transgenic B. napus < p HB transgenic B. napus and WT. Water stress increased the volumetric elastic modulus of cell wall, value of elastic modulus of Os TIP1;1 transgenic B. napus was lowest, and there was no significant difference among these material. And the half time of water exchange were respresented as Os TIP1;1 transgenic B. napus < Os TIP3;1 and Os TIP3;2 transgenic B. napus < p HB transgenic B. napus and WT, values of half time were 1.44 s, 2.04 s, 2.06 s.Under normal condition, the hydraulic conductivity(Lp) of five materials were respresented as Os TIP1;1 transgenic B. napus > Os TIP3;1 and Os TIP3;2 transgenic B. napus > p HB transgenic B. napus and WT. Under water stress, the cell hydraulic conductivity of Os TIP1;1 transgenic B. napus was highest, its value was 0.56×10-6m·s-1·MPa-1; the second were Os TIP3;1 and Os TIP3;2 transgenic B. napus, their valus about 0.38×10-6m·s-1·MPa-1; p HB transgenic B. napus and WT were lowest, their values were 0.36×10-6m·s-1·MPa-1.The results showed that Os TIP1;1 ecotopic expression could significantly improve efficiency of water transport on root cortex cell of transgenic B. napus. Under normal culture condition, the ability of water transport of Os TIP3;1 and Os TIP3;2 transgenic B. napus were higher than p HB transgenic B. napus and WT, and this phenomenon may be related to the interaction of TIPs and PIPs.The results explained that Os TIP1;1, Os TIP3;1 and Os TIP3;2 ectopic expression have an influence on root water transportation of Brassica napus at cell level, provided a theory basis to further understand the specific function of different TIPs isforms. |
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