Genome-wide identification and characterization of barley bHLH transcription factors and their expression in response to low nitrogen stress

Abstract

Background: Improvement of low nitrogen (LN) tolerance or nitrogen use efficiency (NUE) in crops is imperative for environment-friendly agriculture development. The basic helix–loop–helix (bHLH) transcription factors are involved in multiple abiotic stress, suitable as the candidate genes for improving LN tolerance. Little research was done on characterization of bHLH gene family and their response to LN stress in barley.Results: In this study, 168 bHLH genes were identified in barley through genome-wide analysis. HvbHLH proteins were classified into 26 subfamilies based on phylogenetic analysis with bHLH proteins from Arabidopsis thaliana and rice. The analysis of conserved motifs and gene structures supported the evolutionary relationships among these HvbHLH proteins. Further, analysis of stress-related cis-elements in the promoter regions showed that bHLH proteins in barley are probably involved in multiple stress responses. Finally, at least 16 bHLH genes were differentially expressed in two barley genotypes differing in LN tolerance under LN stress. Dynamic expression analysis showed that these differentially expressed genes (DEGs) differed between the two barley genotypes in response to LN stress.Conclusion: It is the first genome-wide analysis of bHLH family genes in response to LN stress in barley. The results indicate the distinct difference among HvbHLH genes in response to various abiotic stresses. The HvbHLHs specifically expressed in the LN-tolerant barley genotype XZ149 identified herein may be valuable for future function analysis of HvbHLH genes under LN stress and breeding for barley cultivars with LN tolerance.