Genome-Wide Identification of the NAC Gene Family in Brassica rapa (L.) and Expression Pattern Analysis of BrNAC2s

Flowers are one of the most important organs in plants. Their development serves as a key indicator of the transition from vegetative to reproductive growth and is regulated by various internal signals and environmental factors. NAC (NAM, ATAF, CUC) transcription factors (TFs) play a crucial regulatory role in floral organ development; however, research on the analysis and identification of the NAC TF family in Chinese cabbage (Brassica rapa L.) remains limited. In this study, we performed a comprehensive genome-wide analysis of NACs in B. rapa and identified 279 members of the BrNAC gene family. Their physicochemical properties, domain structure, collinearity relation, and cis-regulatory elements were evaluated. Phylogenetic analysis indicates that NAC proteins from Arabidopsis, B. rapa, B. oleracea, and B. nigra can be classified into seven distinct clades. BrNACs exhibit a tissue-specific expression, and nine BrNACs being specifically expressed in the inflorescence. Furthermore, nine flower-related BrNACs were selected for RT-qPCR analysis to validate their expression profiles. BrNAC2s has been cloned to investigate their subcellular localization, and examine the expression patterns of their promoters in Arabidopsis inflorescences. BrNAC2a and BrNAC2c are highly expressed in stamens while BrNAC2b exhibits elevated expression in pistils and pedicel. Collectively, our findings enhance the understanding of the BrNAC family and provide a foundation for future studies on the molecular mechanisms of BrNACs in floral development.