Genome-wide analysis of evolution and expression profiles of NAC transcription factor gene family in Juglans regia L.

NAC transcription factors may play important roles in the biological processes in Persian walnut. A total of 102 JrNAC s were identified in Persian walnut. The conserved domains, transcriptome profile, expression analysis, and interaction network suggest that JrNAC1-4 plays potential roles in Persian walnut flowering development. NACs are plant-specific transcription factors that participate in various plant developmental processes such as flowering, plant growth regulation, and development. We identified and analyzed the evolution and expression profiles of NAC genes in Juglans regia. The main objectives were to identify the NAC transcription factors and verify the expression levels in different tissues and female flowers in developmental stages in Persian walnut. We identified NAC transcription factors in J. regia based on the genome-wide analysis. We analyzed the phylogenetic relationships, conserved domain, chromosome location, gene structure, and gene collinearity of JrNACs. We also verified the JrNAC expression levels based on transcriptome analysis and qRT-PCR. We identified 102 NAC genes in J. regia and divided them into ten subfamilies. A total of 30 pairs of JrNAC genes were expanded by whole-genome duplications (WGDs) and one pair of genes (JrNAC2-10 and JrNAC9-8) as a tandem duplication in Persian walnut. Collinearity analysis results indicate that a large number of syntenic relationship events existed between J. regia and Populus trichocarpa. We found that JrNAC1-4 and JrNAC2-6 were expressed significantly higher in female flowers based on both transcriptome and qPCR analysis. We further identified that JrNAC2-9 and JrNAC9-6 were highly expressed at the end period of flowering stages. A total of 102 JrNACs were identified in the Persian walnut genome. These genes were conserved in plants for collinearity analysis, which was performed within the genome and other genomes (P. trichocarpa, Olea europaea, and Quercus robur). A total of 24 NAC transcription factors were highly expressed in female and male flowers, and these transcription factors play a role in J. regia flowering.