Transcriptome-wide identification, classification, and characterization of NAC family genes in Bamboo Bambusa emeiensis

The NAC (NAM-ATAF1/2-CUC) transcription factors (TFs) regulate numerous biological processes, such as growth, development, and stress responses. The yield and quality of Bambusa emeiensis, an economically important bamboo, decrease under stress caused by insect herbivores, such as Cyrtotrachelus buqueti. In the present study, 33 BeNACs, including 4 membrane-associated TFs, were identified in B. emeiensis transcriptome. Phylogenetic analysis revealed that BeNACs and their Arabidopsis thaliana counterparts clustered into 4 major groups, which were subdivided into 17 subgroups. Conserved motif and phylogenetic analyses revealed that BeNACs with close evolutionary relationships contained highly similar motifs. The N-terminal regions of BeNACs had NAC domains. In addition, the C-termini and transmembrane domains of four BeNACs contained transmembrane motifs. Transcriptome analysis revealed that majority of BeNACs were highly expressed under herbivory. The expression levels of eight BeNACs, including predicted stress-related and membrane-bound BeNACs, in bamboo shoots, shells, trichomes, and leaves and under two treatments (fed and unfed) were assessed through quantitative real-time polymerase chain reaction. Several BeNACs (BeNAC4, 10, 19, and 24) were considered as closely related to responses to herbivore. This study lays a foundation for future study of BeNACs' functions in bamboo development and stress response.