Genome-wide identification of NAC transcription factor family and expression analysis of ATAF subfamily members under abiotic stress in eggplant

NAC proteins, as one of the largest plant-specific transcription factors, play key roles in plant growth, development process, and various abiotic/biotic stresses. In this study, 90 NAC transcription factors (TFs) were identified in the eggplant genome, among them, 80 NAC genes from eggplant (SmNAC) were anchored unevenly in 12 chromosomes, but 10 SmNAC genes were mapped on unanchored scaffolds. Phylogenetic analysis indicated that only fifty-nine SmNAC genes were divided into 14 different subfamilies. Gene structure analysis revealed that the number of exons ranged from 1 to 16. Motif analysis revealed that the identified SmNAC transcription factors included the conserved NAC domain and motif2 was the conserved motif. In aspects of gene duplication analysis, five pairs of tandem replications and three pairs of fragment replications were identified in eggplant genome. Subsequently, 49 SmNAC genes were collinear with NAC genes from Arabidopsis or tomato, moreover, seven SmNAC genes were collinear with NAC genes in other two species. In addition, expression patterns of SmNAC genes were analyzed in vegetative and reproductive organs, at different developmental stages. Nine genes were not expressed in all of the examined developmental stages, 36 SmNAC genes were ubiquitously expressed in all eggplant organs/tissues, but differentially expressed in different tissues, and other 45 SmNAC genes detected in some tissues declared their involvement in the growth and development of certain tissues. Following further qRT-PCR analysis of SmNAC19, SmNAC31 and SmNAC75, belonging to ATAF subfamily, exhibited a large diversity in expression patterns, indicating their involvement in the regulation of different abiotic stresses. This study would help to further understand and enrich the physiological function of the SmNAC gene family in eggplant, and could provide high-quality genetic resources for eggplant genetics and breeding.