The DNA-binding with one zinc finger (Dof) family of plant-specific transcription factors has a variety of important functions in gene transcriptional regulation, development, and stress responses. However, the structure and expression patterns of Dof family have not been identified in Cleistogenes songorica, which is an important xerophytic and perennial gramineous grass in desert grassland. In this study, 50 Dof genes were identified in C. songorica and could be classified into four groups. According to genome-wide analysis, 46 of 50 Dof genes were located on 20 chromosomes, and the gene structure and conserved protein motif of these proteins were analyzed. In addition, phylogenetic analysis of Dof genes in C. songorica, Arabidopsis thaliana, Oryza sativa, and Brachypodium distachyon estimated the evolutionary relationships, and these genes were grouped into seven clusters. Moreover, the expression profiles of these Dof genes in C. songorica were analyzed in response to high/low temperature, salinity, and ABA treatments. These results will provide valuable information for future studies on gene classification, cloning, and functional characterization of this family in C. songorica.

Background: As global warming continues, heat stress (HS) is becoming an increasingly significant factor limiting plant growth and reproduction, especially for cool-season grass species. The objective of this study was to determine the transcriptional regulatory network of Cleistogenes songorica under HS via transcriptome profiling, identify of gene families and comparative analysis across major Poaceae species. Results: Physiological analysis revealed significantly decreased leaf relative water content (RWC) but increased proline (Pro) content in C. songorica under 24 h of HS. Transcriptome profiling indicated that 16,028 and 14,645 genes were differentially expressed in the shoots and roots of C. songorica under HS, respectively. Two subgenomes of C. songorica provide equal contribution under HS on the basis of the distribution and expression of differentially expressed genes (DEGs). Furthermore, 216 DEGs were identified as key evolutionarily conserved genes involved in the response to HS in C. songorica via comparative analysis with genes of four Poaceae species; these genes were involved in the ‘response to heat’ and ‘heat acclimation’. Notably, most of the conserved DEGs belonged to the heat-shock protein (HSP) superfamily. Similar results were also obtained from co-expression analysis. Interestingly, hub-genes of co-expression analysis were found to overlap with conserved genes, especially heat-shock protein (HSP). In C. songorica, 84 HSP and 32 heat-shock transcription factor (HSF) genes were identified in the allotetraploid C. songorica genome, and might have undergone purifying selection during evolutionary history based on syntenic and phylogenetic analysis. By analysing the expression patterns of the CsHSPs and CsHSFs, we found that the transcript abundance of 72.7% of the CsHSP genes and of 62.5% of the CsHSF genes changed under heat stress in both the shoots and roots. Finally, a core regulatory network of HS was constructed on the basis of the CsHSP, CsHSF and other responsive genes in C. songorica. Conclusions: Regulatory network and key genes were comprehensively analysed and identified in C. songorica under HS. This study improves our knowledge of thermotolerance mechanisms in native grasses, and also provides candidate genes for potential applications in the genetic improvement of grasses.