Expression analysis of the duplicated genes in the NAC transcription factor gene family related to the drought stress response in peanuts (Arachis hypogaea)

Abstract

NAC has been considered one of the largest transcription factor families in plant species. In peanut (Arachis hypogaea), 29 members of the AhNAC gene family have been identified and characterized. However, the information of their functions related to the mechanism of the stress response has been reported. In this study, a total of seven duplication events, which occurred from the segmental duplication, has been predicted in the AhNAC gene family in peanuts. The Ka\Ks ratios revealed that natural selection prevented the presence of the point mutations in the most duplicated genes, consequently, maintaining their structure and function during evolution. Based on the unrooted phylogenetic tree between AhNAC proteins in peanuts and 23 drought-responsive CaNAC in chickpea (Cicer arietinum), we proposed 12 members of the AhNAC that potentially share similar functions with well-characterized NAC in chickpea. Furthermore, various hormone- and drought-responsive cis-regulatory elements have been found in the promoter regions of these candidate genes. Re-analysis of the previous RNA-Seq demonstrated that the majority of the candidate AhNAC genes were responsive to the osmotic stress. Taken together, our study could provide an important foundation for further functional characterization towards the improvement of stress tolerance in peanuts.