Molecular evolution and diversity of dimeric alpha-amylase inhibitor gene in Kengyilia species (Triticeae: Poaceae)

- Kengyilia species from the Central Asia and the Qinghai-Tibetan Plateau had different origin regarding the P genome.
- The differentiation of Y genome happened after polyploidization between Roegneria and Kengyilia.
- Purifying selection dominated the DAAI gene members and the St- DAAI gene was evolving at faster rate than the P- and Y- DAAI genes in Kengyilia.

Kengyilia Yen et J. L. Yang is a group of allohexaploid species with StYP genomic constitutions in the wheat tribe. To investigate the evolution and diversity of dimeric alpha-amylase inhibitor genes in the Kengyilia, forty-five homoeologous DAAI gene sequences were isolated from sampled Kengyilia species and analyzed together with those of its close relatives. These results suggested that (1) Kengyilia species from Central Asia and the Qinghai-Tibetan Plateau had different origins from those of the geographically differentiated P genome; (2) the St and P genomes of Kengyilia were donated by Pseudoroegneria and Agropyron, respectively, and the Y genome had an independent origin and showed an affinity with the St genome; (3) purifying selection dominated the DAAI gene members and the St-DAAI gene was evolving at faster rate than the P- and Y-DAAI genes in Kengyilia; and (4) natural selection was the main factor on the codon usage pattern of the DAAI gene in Kengyilia.