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 (<i>Brassica rapa</i> L.) remains limited. In this study, we performed a comprehensive genome-wide analysis of <i>NACs</i> in <i>B. rapa</i> and identified 279 members of the <i>BrNAC</i> gene family. Their physicochemical properties, domain structure, collinearity relation, and <i>cis</i>-regulatory elements were evaluated. Phylogenetic analysis indicates that NAC proteins from <i>Arabidopsis</i>, <i>B. rapa</i>, <i>B</i>. <i>oleracea</i>, and <i>B</i>. <i>nigra</i> can be classified into seven distinct clades. <i>BrNACs</i> exhibit a tissue-specific expression, and nine <i>BrNACs</i> being specifically expressed in the inflorescence. Furthermore, nine flower-related <i>BrNACs</i> were selected for RT-qPCR analysis to validate their expression profiles. <i>BrNAC2s</i> has been cloned to investigate their subcellular localization, and examine the expression patterns of their promoters in <i>Arabidopsis</i> inflorescences. <i>BrNAC2a</i> and <i>BrNAC2c</i> are highly expressed in stamens while <i>BrNAC2b</i> exhibits elevated expression in pistils and pedicel. Collectively, our findings enhance the understanding of the <i>BrNAC</i> family and provide a foundation for future studies on the molecular mechanisms of <i>BrNACs</i> in floral development.