Transcriptome analysis of transcription factor genes under multiple abiotic stresses in Populus simonii × P.nigra

Transcription factor (TF) genes play essential roles in abiotic stress responses as master switches in complex regulatory networks. In the present study, the transcript abundance of 4287 TF genes in Populus simonii × P.nigra were profiled under NaCl, KCl, CdCl₂ and PEG stresses, respectively. A total of 118 up-regulated and 226 down-regulated TFs were identified to be shared in the four stress conditions. Among the top seven TF families (ERF, NAC, WRKY, MYB, bHLH, C2H2, bZIP), there were 76 up-regulated TFs found common in the four stresses, and 67% of them were likely to be involved in stress responses. We identified three TFs, which can enhance stress tolerance of transgenic plants, were members of the most significantly up-regulated genes in the respective TF family. Among them, a highly salt-inducible ERF gene, ERF76, was proved to activate the expression of other TFs in the transgenic poplar lines overexpressing ERF76. Transcriptome analysis indicated there was a synergistic effect of TFs on improving salinity tolerance of the transgenic plants. Of significant interest in the study is the discovery of the role and interactions of various TF genes under multiple stress conditions.