Isolation and characterisation of six putative wheat cell wall-associated kinases

The plant cell wall-associated kinase (WAK) and WAK-like kinase (WAKL) make up a unique group in the receptor-like protein kinase (RLK) superfamily. Previous studies on Arabidopsis have revealed that the WAK gene family members play an important role in both cell elongation and stress response signalling. Here we show that four putative WAKs (TaWAK1, TaWAKL2, TaWAKL3, and TaWAK4) and two WAKLs (TaWAKL1 and TaWAKL2) were isolated from wheat based on the DNA sequence similarity and the protein structure conservation of Arabidopsis WAKs genes. TaWAK1, TaWAK2, TaWAK3 and TaWAKL1 each encode a putative intact protein with the characteristic of the WAK/WAKL gene family members, except for the abbreviated TaWAK4 and TaWAKL2 which were caused by nucleotide mutation and alternative splicing, respectively. Southern analysis revealed that TaWAKL1, TaWAK1, TaWAK2 and TaWAK3 are all multiple-copy members. Real-time PCR analysis revealed that the TaWAK1 and TaWAK3 displayed similar expression patterns, while expressions of TaWAKL1, TaWAKL2, and TaWAK2 were organ specific. Further, we analysed the conservation of introns and intron-exon structure and the putative protein structures between wheat and Arabidopsis, which showed the putative wheat WAKs are different from those of Arabidopsis and make up a new subgroup in the polygenetic tree.