Molecular Plant Breeding 2024, Vol.15, No.3, 90-99 http://genbreedpublisher.com/index.php/mpb 95 4 Role of NAC Transcription Factors in Biotic Stresses Biotic stress is the combined effects of various biological factors that are detrimental to the survival and development of an organism. These effects usually originate from the activities of other organisms, including diseases caused by pathogens (e.g., viruses, bacteria, fungi), pest infestation, disturbance by parasitic organisms, and damage by competing species (e.g., weeds), etc. NAC can be involved in different pathogen stresses in different plants (Figure 2). There are fewer reports in the existing literature related to the involvement of the NAC transcription factor family in the biological responses of plants, and there are either positive or negative regulatory roles of NAC transcription factors in biotic stresses. Figure 2 The role of NAC transcription factors in biological stress (Adopted from Lu et al., 2024) During the long evolutionary process of plants, a fine-tuned system of disease resistance defense has been developed. This system is mainly composed of three disease resistance signaling pathways, namely: a salicylic acid (SA)-dependent signaling pathway, a jasmonic acid (JA)-dependent signaling pathway, and an ethylene-dependent signaling pathway (Zhou et al., 2017). Many NAC proteins regulate plant defense responses to enhance plant disease resistance by activating PRgenes, inducing hypersensitive response (HR) and cell death at the site of infection (Nuruzzaman et al., 2013). It was found that ONAC122 and ONAC131 were induced to be expressed under the infestation of Botrytis cinerea. And, ONAC122 and ONAC131 were induced by salicylic acid, methyl jasmonate, or 1-aminocyclopropane-1-carboxylic acid (precursor of ethylene) treatment (Sun et al., 2013). ONAC066 positively regulates rice resistance to rice blast and leaf blight, and ONAC0666 exerts its disease resistance function by regulating the ABA signaling pathway, sugar and amino acid accumulation in rice (Liu et al., 2018b). In addition, by overexpressing the OsNAC60 gene, the transgenic plant exhibit improved resistance to rice blast, whereas when the miR164a/OsNAC60 regulatory module was dysfunctional, rice was significantly susceptible to Rickettsia spp. infection. Further studies found that Osa-miR164a, on the other hand, promotes the infection of B. oryzae (Wang et al., 2018). Except for rice, some NAC genes of other plants also play an important role in disease resistance response. In B. juncea, BjuNAC62 Δ C can enhance resistance to the black spot pathogen of Chinese cabbage (Mondal et al., 2022). The TaNAC069 gene plays a positive regulatory role in the resistance of wheat to leaf rust (Zhang et al., 2021b). The barley leaf rust resistance gene locus Rph7 has been shown to exhibit abnormally high sequence and haplotype differences, and it shares structural similarities with the N-terminal DNA binding domain of the NAC transcription factor (ANAC019) from Arabidopsis, Rph7 is presumed to be a NAC transcription factor (Chen et al., 2023).
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