耐盐药蒲公英(Taraxacum officinale Weber)愈伤组织筛选及生理生化特性分析

为获得耐1.5% NaCl的药蒲公英(Taraxacum officinale Weber)愈伤组织, 以药蒲公英叶片外植体为材料诱导愈伤组织。以NaCl为选择因子, 从愈伤组织直接筛选。在选择培养基上, 大部分愈伤组织褐化死亡, 个别褐化死亡的愈伤组织周围有少量新的细胞团长出, 将其转接到新鲜的选择培养基上, 每3周继代一次, 经3个月继代筛选获得了耐1.5% NaCl的药蒲公英细胞团。以普通愈伤组织为对照, 发现随着NaCl浓度升高, 耐盐愈伤组织的相对生长率下降但显著高于对照; 且随着盐胁迫处理时间延长持续升高, 而普通愈伤组织对照几乎停止生长, 说明耐盐愈伤组织具有相对稳定的耐盐性。在蛋白水平上, 耐盐愈伤组织与对照愈伤组织差异明显, SDS-PAGE分析显示: 耐盐愈伤组织比对照多出一条34 kD大小的蛋白带, 且30 kD、18 kD左右的蛋白带明显上调。相同处理条件下耐盐愈伤组织脯氨酸的增加幅度高于对照。盐胁迫条件下, 耐盐愈伤组织的超氧化物歧化酶(Super oxidase dimutase, SOD)、过氧化物酶(Peroxidase, POD)和过氧化氢酶(Catalase, CAT)活性明显高于对照,且随着处理时间的延长和盐浓度的增加呈现升高的趋势, 而对照则呈现先升高后下降的趋势。结果说明耐盐愈伤组织一方面通过小分子有机溶质如脯氨酸的方式调节其渗透平衡, 另一方面还可通过提高抗氧化能力降低盐分造成的次级伤害。积累蛋白也可能是耐盐愈伤组织调节渗透平衡的一种方式。通过生理生化分析确定我们获得的耐盐愈伤组织为耐盐变异体。

Selection and Characterization of Salt-tolerant Calli of Taraxacum officinale

In order to obtain salt-tolerant calli of Dandelion (Taraxacum officinale Weber), calli were induced from leaf explants of Dandelion on Murashige and Skoog's medium supplemented with 2.0 mg/L 6-benzyladenine and 0.5 mg/L 2,4-dichlorophen oxyacetic acid With 1.5% NaCl as selection pressure, most calli became brown and dead, whereas some new cell clusters appeared at the edge of the brown calli after 2 to 3 weeks. The survived cells were picked out and sub-cultured every 3 weeks onto the fresh selection medium and salt-tolerant calli were finally obtained through 4 continuous selections on the selection medium supplemented with 1.5% NaCl. Salt-tolerant calli increased steadily under a fixed NaCl stress though their relative growth rate decreased with increased NaCl concentration whereas the control calli which were sub-cultured by 4 continus selections on salt free medium ceased to grow under the same condition. This result indicated that the salt-tolerance of the selected calli is improved and this character is stable. Compared with the control, the SDS-PAGE pattern of the salt-tolerant calli had a unique 34 kD protein band. Its 30 kD and 18 kD protein bands were up-regulated. Further more, within the NaCl stress range up to 1.5%, the activities of antioxidant enzymes such as super oxidase dimutase, peroxidase and catalase, and the proline contents of the salt-tolerant calli were higher than those of the control. The results indicated that the selected calli with improved and stable salt tolerance were cell variants. The accumulation of the organic compatible solutes including proteins and the enhanced antioxidant capabilities in the salt tolerant calli are the two ways for them to regulate their osmotic homeostasis and alleviate the secondary reactive oxygen spexies damage respectively.