Evolution of the Aux/IAA Gene Family in Hexaploid Wheat
The Aux/IAA (IAA) gene family, involved in the auxin signalling pathway, acts as an important regulator in plant growth and development. In this study, we explored the evolutionary trajectory of the IAA family in common wheat. The results showed ten pairs of paralogs among 34 TaIAA family members. Seven of the pairs might have undergone segmental duplication, and the other three pairs appear to have experienced tandem duplication. Except for TaIAA15-16, these duplication events occurred in the ancestral genomes before the divergence of Triticeae. After that point, two polyploidization events shaped the current TaIAA family consisting of three subgenomic copies. The structure or expression pattern of the TaIAA family begins to differentiate in the hexaploid genome, where TaIAAs in the D genome lost more genes (eight) and protein secondary structures (α1, α3 and β5) than did the other two genomes. Expression analysis showed that six members of the TaIAA family were not expressed, and members such as TaIAA8, 15, 16, 28 and 33 exhibited tissue-specific expression patterns. In addition, three of the ten pairs of paralogs (TaIAA5–12, TaIAA15–16 and TaIAA29–30) showed similar expression patterns, and another five paralog pairs displayed differential expression patterns. Phylogenetic analysis showed that paralog pairs with high rates of evolution (ω > ω 0), particularly TaIAA15–16 and TaIAA29–30, experienced greater motif loss, with only zero to two interacting IAA proteins. In contrast, most paralogous genes with low ω, such as TaIAA5–12, had more complete motifs and higher degrees of interaction with other family members.
KeywordsMolecular evolution Aux/IAA gene family Wheat Expression analysis
This study was funded by the National Key Research and Development Plan of China (2016YFD0102004-07), the National Natural Science Foundation of China (31601307), Shanxi Province Science Foundation for Youths (2015021145), Shanxi Province Natural Science Foundation (201601D102051) and Shanxi Province International Cooperation Project (201603D421003). We thank Dr. Xiaoyan Li (Beijing Anzhen Hospital Affiliated to the Capital Medical University) and Dr. Wenping Zhang (Fujian Agriculture and Forestry University) for their assistance in the RT-PCR experiment.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflict of interest.
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