AtSOS基因在紫花苜蓿中的表达及其耐盐性研究

本研究采用基因工程技术改良紫花苜蓿耐盐性,通过种植转基因耐盐紫花苜蓿达到改良土壤的目的。以紫花苜蓿子叶节为外植体,通过农杆菌介导法将来源于拟南芥的AtSOS1-AtSOS2-AtSOS3多基因表达载体导入阿尔冈金紫花苜蓿中,经PCR检测、抗除草剂筛选和RT-PCR鉴定,获得了能稳定表达的转基因株系。以转基因的紫花苜蓿和野生型紫花苜蓿为材料进行盐处理,每个处理重复3次,测定其生理生化指标、株高、Na⁺和K⁺含量、细胞膜透性、叶绿素含量。结果显示,在不同盐浓度处理下,所有植株的株高均有所增长,但在100和200 mmol·L^-1的NaCl处理下,转基因植株的长势显著高于野生型植株;随着处理时间的增加,所有植株的叶绿素含量均呈先上升后下降的趋势,且野生型植株叶绿素含量均低于转基因植株;在100和200 mmol·L^-1的NaCl处理下,转基因植株的细胞膜透性、超氧化物歧化酶活性和脯氨酸含量的增加量均小于野生型植株,而过氧化物酶、过氧化氢酶活性和可溶性糖含量的增加量均大于野生型;各植株中丙二醛含量均下降,且野生型植株下降的更为明显;盐处理后,转基因植株根系中Na⁺的积累比野生型植株少,而K⁺的吸收多于野生型植株。转AtSOS基因的紫花苜蓿通过发挥AtSOS途径的作用,促进了植物体将细胞内的Na⁺外排,从而减轻盐胁迫对植物体的伤害,提高了转基因植株的耐盐性。

The expression of the salt tolerance gene AtSOS in Medicago

In this study, alfalfa was genetically engineered to improve its salt tolerance. The SOS1-SOS2-SOS3 genes from Arabidopsis thaliana were incorporated into Algonquin using tumefaciens-mediate transformation technology. Transgenic plants were identified by PCR, herbicide resistance screening and RT-PCR. The salt resistance of the transgenic plants was evaluated by exposing them to different concentration (100, 200 and 300 mmol·L^-1) of NaCl for 6 days and comparing them to unmodified plants. Physiological and biochemical indexes, plant height, Na⁺ and K⁺ content, cell membrane permeability and chlorophyll content were measured. The results showed that under different salt treatments, the height of all plants increased but transgenic plant height was significantly higher than that of unmodified plants at 100 and 200 mmol·L^-1 NaCl. After salt exposure the chlorophyll content of all plants initially increased before declining but the chlorophyll content of unmodified plants was lower than that of transgenic plants. Under 100 and 200 mmol·L^-1 NaCl treatments, membrane permeability, superoxide dismutase activity and proline content of transgenic plants were lower than that of unmodified plants. However, peroxidase activity, catalase activity and soluble sugar were higher than that of unmodified plants. Malondialdehyde content declined in all plants but the decline was greater in unmodified plants. The accumulation of Na⁺ in roots of transgenic plants was less than in unmodified plants, while K⁺ content was more than that of unmodified plants. Transgenic plants displayed increased Na⁺ efflux, reducing cellular ion toxicity, alleviating the damage from salt stress.