Analysis of three types of resistance gene analogs in PmU region from Triticum urartu

Resistance gene analog (RGA) screening of mapped disease-resistant genes not only helps to clone these genes but also helps to develop efficient molecular markers for resistance breeding. The present study focused on the PmU region located on chromosome 7A(u)L of Triticum urartu, and recently, a nucleotide binding site (NBS)-encoding gene, Pm60, was cloned from the same chromosome arm. In this research, NBS, protein kinase (PK), and ATP-binding cassette (ABC), the three disease resistance-related gene families, were analyzed within PmU region by using informatics tools, and an expression experiment was conducted to verify their functions in vivo. Comparative genomic analysis revealed that 126 RGAs were included on chromosome 7A(u)L, and 30 of the RGAs as well as Pm60 were found in the PmU region. Transcriptome database analysis of T. urartu revealed 14 PmU-RGAs with expression data, and three PmU-NBSs exhibited significant changes in expression after inoculation with Blumeria graminis f. sp. tritici (Bgt); TRIUR3_14879 was up-regulated, while TRIUR3_00450 and TRIUR3_06270 were down-regulated. Cluster analysis showed that these three PmU-NBSs were clustered far from the cloned wheat resistance genes. Then, qRT-PCR was performed to investigate the expression of 14 PmU-RGAs and Pm60 after inoculation with Bgt race E09; the results showed that Pm60 was specifically expressed in UR206 which carrying PmU, but not in susceptible UR203; while TRIUR3_14879 was significantly up-regulated and TRIUR3_00450 was down-regulated in UR206 after inoculation. These results indicated that PmU is Pm60, and TRIUR3_14879 and TRIUR3_00450 may also be involved in the defense against Bgt.