( 2 ) at translation level plant mutual sequence of starting translation aaca was added to start codon of t - pa gene by pcr ampliation and plant expression vector pbet was constructed ( 2 )在翻译水平上通过pcr扩增的方式在t - pa基因起始密码子处添加了植物翻译起始共有序列aaca ，构建了植物表达载体pbet 。
