Background: The basic helix-loop-helix (bHLH) transcription factor is one of the most important
gene families in plants, playing a key role in diverse metabolic, physiological, and developmental
processes. Although it has been well characterized in many plants, the significance of the
bHLH family in barley is not well understood at present.
Methods: Through a genome-wide search against the updated barley reference genome, the genomic
organization, evolution and expression of the bHLH family in barley were systematically analyzed.
Results: We identified 141 bHLHs in the barley genome (HvbHLHs) and further classified them into
24 subfamilies based on phylogenetic analysis. It was found that HvbHLHs in the same subfamily
shared a similar conserved motif composition and exon-intron structures. Chromosome distribution
and gene duplication analysis revealed that segmental duplication mainly contributed to the expansion
of HvbHLHs and the duplicated genes were subjected to strong purifying selection. Furthermore, expression
analysis revealed that HvbHLHs were widely expressed in different tissues and also involved
in response to diverse abiotic stresses. The co-expression network was further analyzed to underpin
the regulatory function of HvbHLHs. Finally, 25 genes were selected for qRT-PCR validation, the expression
profiles of HvbHLHs showed diverse patterns, demonstrating their potential roles in relation
to stress tolerance regulation.
Conclusion: This study reported the genome organization, evolutionary characteristics and expression
profile of the bHLH family in barley, which not only provide the targets for further functional analysis,
but also facilitate better understanding of the regulatory network bHLH genes involved in stress
tolerance in barley.