Genome-Wide Identification and Characterization of Yellow Horn (Xanthoceras sorbifolia Bunge) NAC Transcription Factor Gene Family against Diverse Abiotic Stresses

Yellow horn (Xanthoceras sorbifolia Bunge) belonging to the Sapindaceae family is a well-known oil-rich seed shrub widely distributed throughout the northern regions of China, which is preferred owing to its exceptional economic, environmental, ecological and ornamental value. The recent completion of yellow horn genome sequencing facilitates a genome-wide survey of yellow horn transcription factor (TF) families. Plant-specific NAC proteins represent a major TF family in regulating diverse plant biological processes at different tissues and developmental stages. However, no detailed information can be obtained concerning the yellow horn NAC (XsNAC) proteins. Given this, we performed a genome-wide survey of XsNAC gene families. In total 103 putative XsNACs genes were identified from yellow horn genome. Phylogenetic analysis performed between NAC proteins of yellow horn and Arabidopsis revealed that these XsNAC proteins can be classified into 12 subgroups. Gene structure analysis revealed that the intron number of XsNAC genes varied from 0 to 12, and most XsNAC genes had two introns. Conserved motif analysis suggested that all putative XsNAC proteins had conserved NAC domain and/or NAM domain. These predicted XsNAC genes were randomly distributed on 15 chromosomes at diverse densities, particularly on chromosome 1, chromosome 7 and chromosome 11. The cis-regulatory elements (CREs) analysis and protein-protein interaction network analysis showed that the XsNAC proteins may involve in many plant physiological and biochemical processes. Transcriptome analysis revealed that XsNAC genes had differential expression profiles in response to various abiotic stresses, implying their key roles in environmental stress responses. This work would lay solid foundation for future functional characterization of XsNAC proteins.