过表达IbOr基因甘薯增强抗盐性的生理机制

Physiological mechanism of enhanced salt stress tolerance in sweet potato(Ipomoes batats L.) with overexpression of IbOr gene

明确转基因甘薯对盐胁迫响应的生理机制,开发种植耐盐性强甘薯对有效利用盐渍化土地和缓解能源危机具有重要的理论与实践意义.以过表达IbOr基因甘薯及其非转基因甘薯为实验材料,通过室内水培试验,研究150mmol/L NaCl胁迫不同时期甘薯叶片光合参数和抗氧化酶活性等变化规律.结果显示,随着盐胁迫时间延长,甘薯叶片中叶绿素、类胡萝卜素含量及叶片净光合速率(P_n)、气孔导度、胞间CO_2浓度、蒸腾速率都显著降低,但转基因甘薯降低幅度更小.盐胁迫3 d后,转基因甘薯叶片中O_2—·和MDA含量分别为61.23μg/g FW和22.51μmol/g FW,而非转基因植株叶片中O_2—·和MDA含量分别达到80.56μg/g FW和31.92μmol,分别是转基因甘薯的1.31和1.42倍,相比于非转基因植株,盐胁迫后转基因甘薯叶片中具有较低水平的O_2—·和MDA含量.甘薯叶片中SOD、POD和CAT的活性在胁迫后都表现出先升高后降低趋势,且转基因甘薯的酶活性显著高于非转基因甘薯.Na^+含量在盐胁迫后也显著升高,胁迫9d后,转基因和非转基因植株叶片中Na^+含量分别达到25.44 mg/g DW和35.08 mg/g DW,分别是处理前的11.47倍和14.83倍,并且转基因甘薯Na^+含量显著低于非转基因甘薯.以上结果说明盐胁迫下转基因甘薯具有较低的活性氧含量并且膜脂的损伤较小,保持了相对较高的叶绿素含量且含较高类胡萝卜素含量进而维持相对较强的光合作用;转基因甘薯抗盐性的增强很可能通过提高甘薯抗氧化胁迫的能力来实现.

Sweet potato is one of the world＇s most impor tant food, feed, industrial materials and bioenergy crops. Comprehensive understanding of the physiological mechanism of whether and how transgenic sweet potato overexpressing IbOr genes enhance the tolerance to salt stress and developing a strong salt tolerant sweet potato has important theoretical and practical significance for effective utilization of saline land and alleviation of the energy crisis. Transgenic（TS） and nontransgenic（NS） sweet potato plants were treated with 150 mmol/L NaCl salt stress. The changes of photosynthetic parameters and the activities of antioxidant enzyme were studied at different times after salinity treatment. With salt stress time extended, chlorophyll and carotenoids content, photosynthetic rate（P_n）, stomatal conductance（Gs）, intercellular CO_2 concentration（Ci）, transpiration rate（Tr） all decreased evidently in both TS and NS sweet potato groups, though only slightly in TS lines. After three days of salt stress, the contents of O_2—·and MDA in TS were 61.23 μg/g FW and 22.51 μmol/g FW, respectively. While the contents of O_2—· and MDA in NS reached 80.56 μg/g FW and 31.92 μmol/g FW. Compared with the NS, TS plants had lower level of O_2—· and malondialdehyde（MDA） contents. After salinity treatment, the activities of SOD, POD and CAT all firstlyincreased, and then decreased slightly, with significantly higher enzyme activities in TS lines than in NT plants. After nine days of salt stress, the Na＋ contents in TS and NS reached 25.44 mg/g DW and 35.08 mg/g DW, being 11.47 and 14.83 times of that before treatment, respectively. The Na＋ content increased evidently in both but significantly higher in NT plants after salt stress. The results indicated that TS plants had lower reactive oxygen species（ROS） level and lipid membrane damage than TS plants. The higher contents of chlorophyll and carotenoids in TS plants may lead to a higher photosynthetic ability than NT plants. Enhancement of salt tolerance in transgenic sweet potato may be achieved mostly by improving antioxidant ability of sweet potato.