Molecular Plant Breeding 2024, Vol.15, No.3, 90-99 http://genbreedpublisher.com/index.php/mpb 92 NAC transcription factors are a family of transcription factors unique to plants and not found in animals or microorganisms, and the NAC family is one of the largest families of transcription factors in plants, with the number of members varying greatly among plant species. For example, in Arabidopsis thaliana, about 150 NAC transcription factors are known; in rice, there are more than 300 NAC family members; and in soybean there are 152 each (Sun et al., 2012); and 163 genes in poplar (Han et al., 2023). The variation in the number of NAC transcription factor families in different plants not only reflects the differences in genome size and complexity, but also plays different roles in plant stress response. 3 Role of NAC Transcription Factors in Abiotic Stresses NAC transcription factors play an important role in abiotic stresses, which mainly include environmental stresses, including drought, salinity, low temperature, high temperature, heavy metal pollution, ultraviolet radiation, and nutrient deficiency. 3.1 Drought stress Drought stress is a phenomenon that affects normal plant growth and development due to a severe shortage of water content in the soil or a reduction in plant-available water caused by environmental conditions. Studies have shown that NAC transcription factors play an important role in regulating plant responses to drought stress. For example, when rice is subjected to drought stress during its reproductive period, overexpression of the stress responsive gene SNAC1 (STRESS-RESPONSIVE NAC1) can improve the drought tolerance of transgenic rice and increase the seed setting rate by 22%~34%. During the nutritional growth period, genetically modified rice also showed excellent drought resistance. Compared to wild-type rice, genetically modified rice has significantly increased sensitivity to abscisic acid (ABA), and research has found that, The SNAC1 gene is mainly induced and expressed in guard cells under drought conditions, and its encoded protein is a transcriptional activating NAM ATAF and CUC (NAC) transcription factors effectively slow down water loss and improve plant drought resistance by closing stomatal pores more frequently, but this process did not significantly affect their photosynthesis rate (Hu et al., 2006). And in sweet potatoes, there is a pressure induced IbNAC3, which is a transcription activator located in the nucleus and contains a unique activation domain that can interact with ANAC011 The interaction between ANAC072, ANAC083, ANAC100, and NAP enhances plant tolerance to drought environments in Arabidopsis by overexpressing IbNAC3 (Meng et al., 2022). In addition, SlNAC6 (SlNAC6-RNAi) plays an important role in tomato development, drought stress response, and fruit ripening. Studies have shown that some of its effects may be achieved through the regulation of ABA mediated pathways. Overexpression of SlNAC6 leads to a decrease in water loss rate and degree of oxidative damage in tomatoes, as well as an increase in proline content and antioxidant enzyme activity, thereby improving plant drought resistance (Jian et al., 2021). Research has found that six ZmNAC genes found in maize can significantly enhance plant drought tolerance (Wang et al., 2020a). For example, the ZmNAC48 gene in maize has been shown to enhance drought tolerance in Arabidopsis. However, this gene has a natural antisense transcript cis NATZmNAC48, which has a negative regulatory effect on ZmNAC48. When cis-NATZmNAC48 is overexpressed, it interferes with the normal function of ZmNAC48, thereby affecting the normal closure of maize stomata, leading to a decrease in maize drought resistance (Mao et al., 2021). In addition, overexpression of the apple MdNAC29 gene reduces the drought resistance of apple plants, callus tissues, and tobacco, and exhibits higher relative conductivity, malondialdehyde (MDA) content, and lower chlorophyll content under drought stress (Li et al., 2023). Another study found that under drought conditions, overexpression of LpNAC13 in lily bulbs in tobacco resulted in a decrease in plant antioxidant enzyme activity, proline, and chlorophyll content, The MDA content increased, while the results under salt conditions were opposite to those under drought conditions. Overexpression of LpNAC13 in tobacco reduces its drought resistance and enhances its salt tolerance (Wang et al., 2020b). 3.2 Salt stress Salt stress is one of the major abiotic stresses that constrain plant growth and development, and to cope with these unfavorable factors, plants adopt a series of strategies, such as synthesizing osmoregulatory substances, increasing
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