Cloning and Expression Analysis of Wheat Cytokinin Oxidase/Dehydrogenase Gene TaCKX3

Cytokinin oxidase/dehydrogenase plays an important role in regulating plant growth and development. A novel gene of TaCKX3 was cloned from wheat by specific primers designed according to the Triticeae Full-Length CDS Database and was proved to be located on chromosome 7B by analyzing the nulli-tetrasomic lines of “Chinese Spring.” The genomic coding sequence was interrupted by three introns, which were 103, 421, and 458 bp, successively. The complementary DNA sequence of TaCKX3 is 60% identical to that of TaCKX1, and the homology of their deduced proteins is even low. The putative TaCKX3 protein shows highly homology with ZmCKX10 but not with other known cytokinin oxidase/dehydrogenase. However, it contains conserved motifs as other cytokinin oxidase/dehydrogenase, such as flavin adenosine dinucleotide binding domain and cytokinin binding domain. Consistent with ZmCKX10 and AtCKX7, nor the putative TaCKX3 has signal peptide at N terminus, which means that TaCKX3 functions in cytoplasm. Quantitive polymerase chain reaction analysis indicated that the expression of TaCKX3 gene is significantly up-regulated in germinating embryos treated by 6-BA and slightly up-regulated by NaCl or PEG-6000.