Genome-wide identification and expression analysis of NAC transcription factors in Ziziphus jujuba Mill. reveal their putative regulatory effects on tissue senescence and abiotic stress responses.

• A total of 55 NAC transcription factors were characterized in Ziziphus jujuba. • ZjNAC genes have the closest relationship with apple NAC genes. • ZjNAC genes are expressed in various tissues with different developmental stages. • ZjNAC genes response to tissue senescence and various abiotic stresses. Here, 55 genes encoding NAC were identified in the jujube genome. Based on gene structures, protein motifs, and phylogenetic relationships, the jujube NAC family was classified into five groups and 15 subgroups. All ZjNAC genes were distributed on 12 chromosomes and four tandem duplication events were detected. The publicly available RNA-Seq data revealed that ZjNAC genes were differentially expressed in various tissues, but a few genes were highly expressed in fruit. Target genes of NAC were predicted and these genes were enriched in stress responses, catabolism and hydrolysis process. Analyses of the cis -acting elements, homology relationship and genes expression levels under abiotic stresses showed that several genes, such as ZjNAC6 , ZjNAC35 , ZjNAC47 and ZjNAC55 , may be identified to be involved in responses to abscisic acid (ABA) and cold, drought, and salt stresses. Additionally, the differences in expression levels between the young and mature tissues imply ZjNAC genes may respond to tissue senescence. These results could lay a solid foundation for investigations of the biological roles of NAC, breeding improvement for stress resistance and retarding senescence in jujube. [ABSTRACT FROM AUTHOR]