A tuber mustard AP2/ERF transcription factor gene, , functioning in abscisic acid and abiotic stress responses, and evolutionary trajectory of the homologous genes in species.

The AP2/ERF superfamily of transcription factors is one of the largest transcription factor families in plants and plays an important role in plant development processes and stress responses. In this study, , an AP2/ERF superfamily gene, from tuber mustard ( var. Tsen et Lee), sharing high amino acid sequence similarity with the ( AP2-like abscisic acid repressor 1) gene, were performed functional research, and the homologous genes in species were identified and performed phylogenetic analysis. The promoter sequence of contained many phytohormone- and stress-related cis-elements; ABA (abscisic acid) and abiotic stresses can induce expression in tuber mustard; overexpression of in can alleviate plant sensitivity to ABA and salt and osmotic stresses, and the alleviation may be due to changes in stress/ABA-induced gene expression. These results indicated that functions in ABA and abiotic stress responses. By BLAST searches against the genome database of five species (three diploids, , , and , and two allotetraploid, and ) using the protein sequence of , 3, 3, 3, 6, and 5 homologous genes in , , , , and were identified, respectively, and they shared high sequence similarity. By sequence analysis, annotation mistakes of the protein-coding regions of two homologous genes, and , were found and corrected. Then, the evolution analysis of these homologous genes showed that the ancestor of the three diploid species had three homologous genes and each diploid inherited all the three genes from their ancestor; then, allotetraploid inherited all the six genes from and with no gene lost, while allotetraploid inherited all the three genes from and two genes from with one gene lost, indicating that homologous genes possessed greater hereditary conservation in species. The homologous genes between and shared much higher sequence similarity compared to that of in diploid species, indicating that homologous genes in had experienced more rapid evolution, and and may share closer relationship compared to . Moreover, the spatial and temporal expression analysis of six homologous genes of tuber mustard showed that they possessed different expression models. These results imply that homologous genes are important to plants, and they may possess similar function in ABA and abiotic stress responses but play a role in different tissues and growing stages of plant. This study will provide the foundation to the functional research of homologous genes in the species and help to reveal and understand the evolution mechanisms of species.