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 Juglans mandshurica, 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 JmNAC genes in the J. mandshurica genome. Chromosomal location analysis revealed that JmNAC genes were unevenly distributed in 16 chromosomes; the highest numbers were found in chromosomes 2 and 4. Furthermore, according to the homologues of JmNAC genes in Arabidopsis thaliana, a phylogenetic tree was constructed, and the results demonstrated 114 JmNAC genes, which were divided into eight subgroups. Four JmNAC gene pairs were identified as the result of tandem duplicates. Tissue-specific analysis of JmNAC genes during different developmental stages revealed that 39 and 25 JmNAC 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 JmNAC genes were common in fruit ripening stage in walnut exocarp and embryos, which demonstrated that these genes were positively correlated with fruit development in J. mandshurica. This study provides new insights into the regulatory functions of JmNAC genes during fruit development in J. mandshurica, thereby improving the understanding of characteristics and evolution of the JmNAC gene family.
Highlights
The family name is derived from the common proteins of no apical meristem (NAM) from Petunia hybrida, ATAF1–2 and cup-shaped cotyledon (CUC) from Arabidopsis thaliana, which prompted the formation of a conserved NAC domain [6,7]
The names of JmNAC genes were encoded from JmNAC1 to JmNAC114 according to the gene annotation information (Table S1)
The results showed that five JmNAC genes including JmNAC085, JmNAC011, JmNAC097, JmNAC102, and JmNAC055 may be the key nodes in this network, which interacted with other Transcription factors (TFs) to form a complicated regulatory network
Summary
Transcription factors (TFs) are proteins that bind to cis-acting elements in the promoter regions and play a vital regulatory role in abiotic and biotic stress responses in many plants [1,2]. The C-terminal contains highly varying transcriptional regulatory regions and is involved in DNA binding [10,11] Owing to their crucial function in the formation of the embryos and flowers of petunias, NAC TFs were widely studied, and multiple reports identified its key role in plant growth and development [12,13]. Some genes involved in plant hormone biosynthesis and signal transduction are directly regulated by NAC transcription factors during fruit development and ripening process [37]. This study will improve the understanding of the functional characteristics of JmNAC genes to identify their role in the development of walnut exocarp and embryos in J. mandshurica and will lay a foundation for further study of molecular mechanisms of fruits
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