Genome-Wide Identification of NAC Transcription Factor Family in Juglans mandshurica and Their Expression Analysis during the Fruit Development and Ripening

Abstract

The NAC (NAM, ATAF and CUC) gene family plays a crucial role in the transcriptional regulation of various biological processes and has been identified and characterized in multiple plant species. However, genome-wide identification of this gene family has not been implemented in <i>Juglans mandshurica</i>, and specific functions of these genes in the development of fruits remain unknown. In this study, we performed genome-wide identification and functional analysis of the NAC gene family during fruit development and identified a total of 114 <i>JmNAC</i> genes in the <i>J. mandshurica</i> genome. Chromosomal location analysis revealed that <i>JmNAC</i> genes were unevenly distributed in 16 chromosomes; the highest numbers were found in chromosomes 2 and 4. Furthermore, according to the homologues of <i>JmNAC</i> genes in <i>Arabidopsis thaliana</i>, a phylogenetic tree was constructed, and the results demonstrated 114 <i>JmNAC</i> genes, which were divided into eight subgroups. Four <i>JmNAC</i> gene pairs were identified as the result of tandem duplicates. Tissue-specific analysis of <i>JmNAC</i> genes during different developmental stages revealed that 39 and 25 <i>JmNAC</i> genes exhibited upregulation during the mature stage in walnut exocarp and embryos, indicating that they may serve key functions in fruit development. Furthermore, 12 upregulated <i>JmNAC</i> genes were common in fruit ripening stage in walnut exocarp and embryos, which demonstrated that these genes were positively correlated with fruit development in <i>J. mandshurica</i>. This study provides new insights into the regulatory functions of <i>JmNAC</i> genes during fruit development in <i>J. mandshurica</i>, thereby improving the understanding of characteristics and evolution of the <i>JmNAC</i> gene family.