The nascent polypeptide-associated (NAC) complex was described in yeast as a heterodimer composed of two subunits, α and β, and was shown to bind to the nascent polypeptides newly emerging from the ribosome. Although NAC function was widely described in yeast, less is known about its role in plants. The knock down of individual NAC subunit(s) led usually to a higher sensitivity to stress. In Arabidopsis thaliana genome, there are five genes coding for NACα subunit, and two genes coding for NACβ. Double homozygous mutant in both genes coding for NACβ was acquired, which showed a delayed development compared to the wild type, had abnormal number of flower organs, shorter siliques and greatly reduced seed set. Herein, both NACβ genes were characterized by complementation analysis, overexpression, subcellular localization, and promoter analysis. Since flowers were the most affected organs by nacβ mutation, the flower buds transcriptome was identified by RNA sequencing, and their proteome by gel-free approach. The differential expression analyses of transcriptomic and proteomic datasets suggest the involvement of NACβ subunits in stress responses and male gametophyte development.