Genome-Wide Identification and Expression Analysis of the NAC Transcription Factor Family in Pineapple

NAC [no apical meristem (NAM), Arabidopsis transcription activation factor (ATAF1/2) and cup-shaped cotyledon (CUC2)] proteins is one of the largest classes of plant specific transcription factors and plays a critical role in plant growth, development process, and abiotic/biotic stresses. In this study, 73 NAC genes (AcNACs) were identified from the pineapple genome. Phylogenetic analysis showed that AcNACs could be divided into 13 subgroups. Gene structure analysis showed that the number of introns varied from 0 to 12. Motif analysis revealed that all of the identified AcNACs had the conserved NAC domain and motif 6 is the conserved motif. Most of the AcNACs were located in chromosome except AcNAC68, AcNAC70, AcNAC71 and AcNAC72, which were presented on unanchored scaffolds. Furthermore, we analysed AcNAC expression patterns in vegetative organs and in sexual organs, namely ovules and stamens, at different developmental stages respectively. Five AcNAC genes (AcNAC6; AcNAC7; AcNAC48; AcNAC70; AcNAC71) were not detected in vegetative organs. AcNAC55 exhibited the highest expression level in vegetative organs. Six AcNAC genes (AcNAC11, AcNAC18, AcNAC27, AcNAC28, AcNAC40, and AcNAC55) showed high expression levels in all reproductive organs. Seven AcNAC genes (AcNAC26, AcNAC34, AcNAC40, AcNAC43, AcNAC63 and AcNAC65) were induced under abiotic stresses. These data provided a new insight of NAC gene family in pineapple and revealed the diverse function of NAC transcription factors in pineapple growth and development.