Genome-wide identification of the NAC transcription factor family in Hedychium coronarium and its functional analysis in inflorescence development

The NAC gene family is widely distributed in plants and plays essential regulatory roles in diverse biological processes, including growth, development, and responses to abiotic stresses. However, systematic characterization of the NAC gene family in Hedychium coronarium remains limited, and key members involved in inflorescence architecture formation and its regulatory divergence have not yet been clearly identified. In this study, we systematically identified members of the NAC gene family ( HcNAC ) in H. coronarium , characterized their features, and screened candidate genes potentially involved in the regulation of inflorescence architecture. A total of 149 NAC genes were identified in the H. coronarium genome, of which 126 were mapped to 17 chromosomes, while 23 were located on unanchored scaffolds. Phylogenetic analysis classified these genes into 16 subfamilies, and members within the same subfamily exhibited relatively high structural conservation. Promoter cis-acting element analysis revealed that HcNAC genes were enriched in hormone-responsive, light-responsive, and abiotic stress-related elements. Synteny analysis demonstrated that 85 HcNAC genes showed strong collinearity with NAC genes in Musa acuminata . To elucidate the mechanisms underlying different inflorescence types, morphological and cytological comparisons were performed between tubular and imbricate inflorescences. The results showed significant differences in bract arrangement, epidermal cell size, and adaxial - abaxial growth polarity, suggesting that variation in inflorescence architecture is closely associated with the coordinated regulation of cell division and cell elongation. Furthermore, integrated transcriptome differential expression analysis, weighted gene co-expression network analysis (WGCNA), and qRT-PCR validation identified a candidate gene, HcNAC60 . Subcellular localization analysis indicated that HcNAC60 is localized in the nucleus and exhibits strong transcriptional activation activity. Silencing of HcNAC60 significantly reduced bract angle and spacing in tubular inflorescences, while increasing bract width, indicating that HcNAC60 plays a crucial regulatory role in inflorescence architecture formation in H. coronarium . This study systematically elucidates the composition and characteristics of the NAC gene family in H. coronarium and identifies a key regulator of inflorescence architecture formation, HcNAC60 , providing important insights and genetic resources for understanding the molecular mechanisms underlying inflorescence development and for improving floral architecture in H. coronarium .