Characterization and expression pattern analysis of DcNAC gene in somatic embryos of Dendrobium candidum Wall Ex Lindl.

The plant-specific no apical meristem genes are transcription factors that play diverse roles in plant development and stress responses. However, whether the gene family is also involved in somatic embryogenesis remains unknown, and no NAC family genes have been identified from orchid species. Here, we cloned and characterized a new member of NAC family from somatic embryos of Dendrobium candidum. Phylogenetic analysis indicated that DcNAC fell into the NAM subgroup based on similarities in protein sequence. Expression pattern analysis indicated that DcNAC exhibited a specific expression pattern in tissues examined, high levels of DcNAC mRNA was detected in protocorm-like bodies, and predominantly in the shoot apical meristem region as detected by in situ hybrization. Subcellular localization analysis showed that DcNAC protein is restricted in the nucleus through transient expression in Nicotiana benthamiana. Thus, DcNAC is the first NAC family gene isolated from orchid species, and our results provide the foundation for future investigations on the molecular mechanisms of somatic embryogenesis and for genetic improvement of Dendrobium candidum.