Diversity and distribution of Rc1 alleles in Triticum urartu from the Middle East

Abstract

Rc1 (red coleoptile) encode a R2R3-MYB transcription factor TaMYB-A1 in common wheat, but the homologous genes have not been reported in Triticum urartu or Triticum monococcum, both species being sources of the ancient A genome. In this study, four alleles were discovered in 120 T. urartu accessions, and two alleles from nine T. monococcum accessions. The six alleles encoded five proteins because TuMYB-A1-F and TuMYB-A1-C encoded the same protein. All mutated sites in the amino acid sequence of these alleles were out of the R2R3 and transcript activator domains, and did not affect the conserved tryptophan (W) residues nor the “D/ELX2R/KX3LX6LX3R” motif of the MYB proteins. The alleles from T. monococcum were more similar in sequence to TaMYB-B1 and TaMYB-D1 than were those from T. urartu in the phylogenetic tree, while the alleles from T. urartu resembled TaMYB-A1 more closely than did the T. monococcum alleles. TuMYB-A1-C was the most widely distributed allele, and Turkey contained the greatest genetic variation compared with the five other countries in the geographical distribution analysis. Transient expression of TuMYB-A1-D or TuMYB-A1-F induced anthocyanin biosynthesis in white coleoptiles of wheat cultivar ‘Opata’ with the help of ZmR. RT-PCR analysis showed that the transcript level of Rc1 allele in white coleoptiles was clearly lower than in red coleoptiles, suggesting that Rc1 allele plays an important role in anthocyanin biosynthesis in coleoptiles of T. urartu. The allele isolation, phylogenetic analysis, geographical distribution and functional verification should be helpful in understanding the functions of Rc1 alleles and the molecular mechanism underlying the coleoptile color trait in Triticum.