Genome-wide characterization and expression analysis of gene family in physic nut ( L.).

The basic helix loop helix (bHLH) transcription factor perform essential roles in plant development and abiotic stress. Here, a total of 122 bHLH family members were identified from the physic nut ( L.) genomic database. Chromosomal localization results showed that 120 members were located on 11 chromosomes. The phylogenetic tree manifested that the could be grouped into 28 subfamilies. Syntenic analysis showed that there were 10 bHLH collinear genes among the physic nut, and . These genes, except , were highly expressed in various tissues of the physic nut, implying a key role in plant development. Gene expression profiles showed that ten genes (especially , and ) correspond to both salinity and drought stresses; while eight genes only respond to salinity and another eight genes only respond to drought stress. Moreover, the protein interaction network revealed that the are involved in growth, development and stress signal transduction pathways. These discoveries will help to excavate several key genes may involve in salt or drought stresses and seed development, elucidate the complex transcriptional regulation mechanism of genes and provide the theoretical basis for stress response and genetic improvement of physic nut.