摘要
从重金属超富集植物天蓝遏蓝菜(T.caerulescens)Cd胁迫的cDNA文库中,通过基因表达的差异筛选得到的阳性克隆之一,核苷酸序列分析表明,与拟南芥CaM2的相似性高达92%,故命名为TcCaM2(T.caerulescens CaM2,GenBank No.EF053035).其核苷酸序列与迄今已知的钙调蛋白基因同源率在83%以上;其氨基酸序列同源性高达95%以上;与大多数高等植物的CaM,如印度芥菜、拟南芥、水稻等同源性则更高.将TcCaM2基因置于酵母表达启动子之下,构建酵母表达载体,并将其转入重金属敏感型酵母突变菌株,酵母重金属耐受性实验表明,TcCaM2在酵母中的过量表达提高了酵母对Co2+或Ni2+的耐受性,增加了对Cd2+的敏感性,对Zn2+胁迫抗性稍有增加但差异不显著.说明TcCaM2通过其对重金属离子的结合作用及在信号转导系统中的功能,在植物细胞对重金属的富集、耐性中发挥了重要的调节作用.
Calmodulin, the predominant calcium receptor, is one of the best-characterized calcium sensors in eukaryotes which regulates diverse cellular functions by modulating the activity of a variety of enzymes and proteins. Research workers have evidences suggesting Ca^2＋ and calmodulin are involved in various environment stimulation reaction. By differential screen, we isolated a positive clone in the T. caerulescens cDNA library induced in response to Cd^2＋ . The result of cDNA sequence analysis showed that the positive clone shared more than 92 % homologies for nucleotide sequences with CaM2 gene from Arabidopsis thanliana, named TcCaM2. The TcCaM2 gene consists of 447 nucleotides and encodes 149 amino acids, and it shares more than 83% homologies for nucleotide sequences and 95 % for encoding amino acid sequences as compared with those of calmodulin genes of other plants. A yeast-expressed plasmid with TcCaM2 was constructed and transferred into heavy metal sensitive yeast mutant cells. Further study about the growth patterns of TcCaM2-expressed yeast indicated that over expression of TcCaM2 improved Co^2＋ ,Ni^2＋ resistance and increased Cd^2＋ hypersensitivity in the yeast cells. As an important role in the T. caerulescens＇ s response to heavy metal, TcCaM2 can work as a significant gene tool in the phytoremediation of heavy metal pollution.
出处
《中国科学院研究生院学报》
CAS
CSCD
2007年第4期465-472,共8页
Journal of the Graduate School of the Chinese Academy of Sciences
基金
国家自然科学基金资助项目(30370128
30570146)
