烟草NtKAT3基因克隆、序列和表达分析

Cloning,sequence and expression analysis of a potassium channel NtKAT3 in tobacco

钾离子通道对植物体具有重要的生理功能,利用同源克隆的策略从烟草品种K326中获得一个钾离子通道基因,该基因全长1 989 bp,蛋白编码662个氨基酸,分子量75.6 ku,等电点7.2。同源性分析结果显示,该基因与绒毛烟草钾离子通道基因KAT3、林烟草钾离子通道基因KAT3等具有较高的同源性,所以命名为NtKAT3。根据生物信息学分析,NtKAT3具有5个跨膜区,是一个疏水蛋白。基因表达分析表明,NtKAT3在根中的表达量最高,其次是叶、茎和花;烟草幼苗在低钾处理后NtKAT3的表达量先升高后降低,NtKAT3的表达量在12 h时达到最高值,在48 h达到最低值;200 mmol·L^(-1)NaCl处理后,NtKAT3基因表达量在6 h达到最低值,24 h达到最高值,说明该基因表达量受到低钾和盐胁迫诱导。

Potassium channels have important physiological roles in plants. This study obtains a potassium channel gene from the tobacco variety K326 by using homologous cloning strategy. Sequences analysis showed that this gene contains 1 989 bp and encodes a protein consisting of 662 amino acids, the calculated molecular mass was 75. 6 ku and the theoretical isoelectric point （pi） was 7. 2. Homology analysis suggested that the gene had a high homology with the potassium channels KAT3 of both Nicotiana tomentosiformis and Nicotiana sylvestris, so it was named as Nt- KAT3. Protein structure and function analysis showed that NtKAT3 has 5 transmembrane domains, which was a hy-drophobic membrane protein. Expression patterns analysis showed that the highest expression level was observed in the roots, followed by leaves, stems and flowers. Under low potassium condition, the expression level of NtKAT3 in tobacco seedlings increased firstly and then decreased, the highest expression level of NtKAT3 appeared at 12 h , and the lowest level appeared at 48 h. Under 200 mmol？ L 1 NaCl treatment, NtKATi reached the lowest expression level at 6 h, while the highest level appeared at 24 h, which indicated that the gene NtKAT3 can be induced by low potas-sium or salt stress.