Production And Salt Tolerance Evaluation Of Sweetpotato (Ipomoea Batatas (L.) Lam.) Plants Overexpressing IbP5CR, IbERD3, IbELT Or IbNFU1 Gene

The function of IbP5CR, IbERD3, IbELT and IbNFU1 genes isolated at our laboratory was characterized by the Agrobacterium tumefaciens-mediated transformation system of sweetpotato (Ipomoea batatas (L.) Lam.).1. Transgenic sweetpotato cv. Kokei No.14 plants overexpressing IbP5CR gene were developed with A. tumefaciens-mediated transformation. The IbP5CR-overexpressing sweetpotato plants exhibited significantly higher salt tolerance compared with the wild-type (WT). Proline content and superoxide dismutase (SOD) and photosynthetic activities were significantly increased, whereas malonaldehyde (MDA) content was significantly decreased in the transgenic plants. H2O2 was also found to be significantly less accumulated in the transgenic plants than in the WT. Overexpression of IbP5CR up-regulated P5CS gene and down-regulated PDH and P5CDH genes under salt stress. The systemic up-regulation of reactive oxygen species (ROS) scavenging genes was found in the transgenic plants under salt stress. These findings suggest that overexpression of IbP5CR increases proline accumulation, which enhances salt tolerance of the transgenic sweetpotato plants by regulating osmotic balance, protecting membrane integrity and photosynthesis and activating ROS scavenging system.2. Transgenic sweetpotato cv. Shangshu 19 plants exhibiting enhanced salt tolerance were developed using IbERD3 gene with A. tumefaciens-mediated transformation. Proline content and SOD and photosynthetic activities were significantly increased, whereas MDA content was significantly decreased in the transgenic plants than in the WT. Overexpression of IbERD3 up-regulated P5CS, P5CR, SOD, psbA, and PRK genes under salt stress. These results suggest that overexpression of IbERD3 enhances salt tolerance of the transgenic sweetpotato plants by increasing proline accumulation and SOD activity, protecting membrane integrity and photosynthesis activity.3. The production of transgenic sweetpotato cv. Shangshu 19 plants exhibiting enhanced salt tolerance using IbELT gene was achieved through A. tumefaciens-mediated transformation. Proline content and SOD and photosynthetic activities were significantly increased, whereas MDA content was significantly decreased in the transgenic plants than in the WT. Overexpression of IbELT up-regulated P5CS, P5CR, SOD,psbA, and PRK genes under salt stress. These results suggest that overexpression of IbELT enhances salt tolerance of the transgenic sweetpotato plants by increasing proline accumulation and SOD activity, protecting membrane integrity and photosynthesis activity.4. The 4 IbNFUl-overexpressing salt-tolerant sweetpotato lines were evaluated for salt tolerance. The IbNFU1-overexpressing plants exhibited significantly higher salt tolerance compared with the WT under 200 mM NaC1 stress. Reduced ascorbate content was significantly increased and photosynthetic activity was significantly enhanced in the transgenic plants. H2O2 was found to be significantly less accumulated in the transgenic plants than in the WT. Overexpression of IbNFUl up-regulated P5CS and P5CR genes under salt stress. The systemic up-regulation of ROS scavenging genes was also found in the transgenic plants under salt stress. No obvious changes in the level of CMO and BADH expression beween IbNFU1-overexpressing plants and WT plants were found at all time points under salt stress. These findings suggest that IbNFUl gene is involved in sweetpotato salt tolerance and enhances salt tolerance of the transgenic sweetpotato plants by regulating osmotic balance, protecting membrane integrity and photosynthesis and activating ascorbate-mediated ROS scavenging system.