Genome-Wide Identification and Characterization of NAC Transcription Factors in Avocado (Persea americana): Expression Analysis During Fruit Development

Background: The NAC family constitutes one of the largest families of plant-specific transcription factors and plays crucial roles in fruit development, ripening, seed life, and stress responses. However, comprehensive characterization of NAC genes in Persea americana (avocado), an economically important horticultural crop, has been largely unexplored. Methods: We performed a genome-wide identification and systematic characterization of NAC transcription factor (TF) genes in P. americana using blastp analysis, phylogenetic reconstruction, expression profiling and weighted gene co-expression network analysis (WGCNA). Results: A total of 130 NAC genes (PaNACs) were identified and distributed across all 12 chromosomes. Phylogenetic analysis classified these PaNACs into eight distinct subfamilies. WGCNA identified 43 co-expression modules, with 68 PaNAC genes distributed across 24 modules associated with hormone signaling, cell wall modification, secondary metabolism, and fatty acid beta-oxidation. Among 48,785 developmental differentially expressed genes (DEGs), 70 PaNAC genes were differentially expressed, with PaNAC003 and PaNAC002 showing the strongest upregulation and PaNAC023 and PaNAC025 the strongest downregulation. Among 9488 ethylene-responsive DEGs, PaNAC041 was suppressed by ethylene and induced by 1-methylcyclopropene (1-MCP, a competitive inhibitor of ethylene perception), while PaNAC016, PaNAC085, and PaNAC086 showed the opposite pattern. Conclusions: These findings provide a genomic and transcriptional framework for future functional investigation of PaNAC genes and their potential relevance to avocado fruit development and postharvest ripening.