Transcriptomic and Systematic Analyses Reveal TabZIP Family Members Involved in the Response to Different Concentrations of Auxin in Wheat Root

Abstract Background Auxin involved in many aspects of root development and physiology which is considered a potential target for improving crop quality and yield. Yet, there has been no systematic investigation on roots underlying the response to different concentrations of auxin. This study evaluated the effects of different concentrations of auxin on the wheat root transcriptome. We also investigated the wheat bZIP transcription factor family and preliminarily analyzed the structural function of the members responding to different concentrations of auxin. Results In response to 1 µM auxin, 308 and 326 genes whose expression were upregulated and downregulated, respectively, were identified in wheat roots. However, there were 6118 and 2333 genes whose expression were downregulated and upregulated, respectively, in response to 50 µM auxin. GO enrichment and KEGG pathway analyses revealed that the inhibitory effect of 1 µM auxin in roots manifested as an enrichment of the glycolysis/gluconeogenesis and glutathione metabolism pathways. Enrichment of the phenylpropanoid biosynthesis and plant-pathogen interaction pathways in response to 50 µM auxin indicated a stress response. In addition, A total of 176 TabZIP genes were identified from the wheat genome and gene structure and protein motif analyses indicated that closely clustered TabZIP genes were relatively conserved within each subgroup. There are 4 TabZIPs were downregulated in response to 1 µM auxin, 17 TabZIPs were downregulated and 4 TabZIPs were upregulated in response to 50 µM auxin through the transcriptome data. These auxin-responsive TabZIP genes may be used as candidate genes for root regulation. Conclusions The results revealed that the transcriptomes underlying the root regulation in response to these two auxin concentrations were different. These findings provide a comprehensive molecular framework of the auxin regulatory network as well as potential key genes for improving the wheat root system to optimize its absorption of water and nutrients, and finally improve wheat quality and yield.