Molecular Plant Breeding 2024, Vol.15, No.3, 90-99 http://genbreedpublisher.com/index.php/mpb 91 for DNA binding and is the basis for the NAC proteins to recognize and bind specific DNA sequences. The domain contains five subdomains (A to E), including conserved subdomains A, C, and D, and diverse subdomains B and E. Based on differences in sequence homology, this family can be systematically classified into two major categories: the first integrates 14 unique subclassifications, counting TERN, ONAC022, SENU5, NAP, AtNAC3, ATAF, OsNAC3, NAC2, ANAC011, TIP, OsNAC8, OsNAC7, NAC1, and NAM. Different subfamilies of NAC proteins showed functional specificity. For instance, the ATAF subfamily, also known as subfamily III-1, has been substantiated through research to have its members extensively involved in various biotic and abiotic stress responses (Ou et al., 2024); the second group, on the other hand, encompasses four subclassifications, namely ANAC001, ONAC003, ONAC001 and ANAC063 (Lu et al., 2024). Table 1 Non biological stress-related NAC transcription factors NACgene Stress resistance function Species Literature ANAC096 Positive regulation of drought tolerance Arabidopsis thaliana (Xu et al., 2013) OsNAC3 Positive regulation of salt and alkaline tolerance Oryza sativa (Zhang et al., 2021a) ZmNAC074 Positive regulation of heat resistance Arabidopsis thaliana (Xi et al., 2022) GmNAC20 Positive regulation of salt and cold tolerance Arabidopsis thaliana (Hao et al., 2011) CaNAC2 Positive regulation of cold tolerance Capsicum annuum (Guo et al., 2015) AmNAC24 Positive regulation of cold tolerance Ammopiptanthus mongolicus (Dorjee et al., 2024) MsNAC001 MsNAC058 Positive regulation of salt alkaline and drought resistance Medicago sativaL. (Min et al., 2020) Table 2 NAC transcription factors related to biological stress NACgene Stress resistance function Species Literature ANAC019 ANAC055 Changing resistance to gray mold Arabidopsis thaliana (Bu et al., 2008) GhNAC100 Changing resistance to Dahlia wilt pathogen Cotton (Hu et al., 2019) TaNAC069 Enhancing resistance to leaf rust fungus Wheat (Zhang et al., 2021b) The carboxyl-terminus (C-terminus), on the other hand, is the transcriptional activation domain (TAD), which is less conserved and has a high degree of diversity, and plays a decisive role in the functional specificity of transcription factors such as activation or repression of gene expression. For example, the five sub-structural domains (A-E) in Arabidopsis, which are differently conserved, contain multiple chemical modification sites and hydrophobic regions. Subdomain D may be related to DNA binding and nuclear localization, while the C-terminal F and G regions may be related to transcriptional activation functions and secondary growth NAC subfamily delineation (Chen et al., 2009). Figure 1 Structural characteristics of NAC transcription factors (Adopted from Puranik et al., 2012)
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