Molecular Plant Breeding 2024, Vol.15, No.3, 90-99 http://genbreedpublisher.com/index.php/mpb 93 the activity of antioxidant enzymes, and maintaining ionic homeostasis, in order to mitigate the negative effects of saline stress on their growth and development. Some of the NAC transcription factors depend on the ABA pathway to regulate salt tolerance in plants. For example, rice OsNAC3 is an important regulator of ABA signaling response and salt tolerance. the expression of genes such as Os HKT1;4, Oshkt1;5, Oslea3-1, Ospm-1, Ospp2C68, and Osrab-21 reduced its sensitivity to abscisic acid and improved plant tolerance to salt stress (Zhang et al., 2021a). Overexpression of GmSIN1 in soybean promoted root growth and increased yield under salt stress. Its response to salt stress requires rapid induction of ABA (abscisic acid) and ROS (reactive oxygen species). Further studies revealed that GmSIN1, GmNCED3s and GmRbohBs synergistically formed a positive feed-forward regulatory mechanism, which significantly accelerated the process of ABA and ROS accumulation, thereby amplifying salt stress signals and enabling the plant to respond to and adapt to the salt-stressed environment more rapidly (Li et al., 2019). Some NAC transcription factors do not rely on the ABA pathway and regulate plant salt tolerance. Overexpression of Pennisetum glaucumPgNAC21 in Arabidopsis enhances GSTF6 (glutathione s-transfer 6), The expression of COR47 (cold regulated 47) and RD20 (responsive to dehydration 20) enhances plant salt tolerance (Shinde et al., 2019). Overexpression of Ts NAC1 gene in Thellungiella salsuginea and Arabidopsis can enhance plant tolerance to drought, cold, and salt stress, thereby delaying plant growth rate (Liu et al., 2018a). A high salt environment can also induce the expression of OsNAC071 in rice, thereby improving plant salt tolerance (Liu, 2023). In addition, salt stress and alkali stress are two different abiotic stresses, but they are often collectively referred to as salt stress, and alkali stress tends to cause more significant damage to plants (Wang et al., 2017). However, these two stresses often occur together, and high concentrations of salt and alkaline environments can cause multiple adverse effects on plant root cells. It was found that LpNACl3 and LpNAC5 could enhance the seed germination rate under saline and alkaline stress to a certain extent, and significantly enhance the salt and alkali tolerance of transgenic tobacco seedlings, but would reduce their drought tolerance to a certain extent (Wang, 2020). The transgenic tobacco seedlings were found to be more tolerant to salt and alkali. And this phenomenon was also reflected in LpNAC6, where antioxidant enzymes (SOD, POD, CAT) activities, chlorophyll content, proline content and photosynthetic capacity were increased in LpNAC6 transgenic tobacco, while MDA, H2O2 and O2-contents were reduced, which enhanced alkali tolerance, but showed the opposite effect under drought stress (Yan et al., 2022). 3.3 Temperature stress Temperature stress refers to environmental temperatures that exceed the optimal growth range of plants, and includes two main forms of low-temperature stress and high-temperature stress, which can adversely affect plant growth, development, physiology, and survival. Low-temperature stress is also divided into cold damage (0 ℃~15 ℃) and freezing damage (below 0 ℃), both of which can cause different degrees of damage to plants, but the mechanisms are different, with freezing damage involving the formation of ice crystals directly physically damaging the cells, whereas cold damage leads to damage more through disruption of physiological processes Cold damage is more likely to result in injury through disruption of physiological processes (Lu et al., 2024). Overexpression of LlNAC2 in Arabidopsis thaliana enhances the resistance of Lilium lancifolia to cold stress by participating in the DREB/CBF-COR and ABA signaling pathways in cold stress (Yong et al., 2019). CaNAC064 isolated from pepper leaves has transcriptional activation activity at a critical region of 691~1 071 bp, which can interact with low-temperature-induced monomeric-type proteases to positively regulate cold resistance in plants (Hou et al., 2020). At 0 ℃~15 ℃, overexpression of MdNAC104 enhanced the antioxidant enzyme activities of apple plants and attenuated the damage of PSII, thereby enhancing the cold tolerance of the plants. In addition, below 0 ℃, overexpression of MdNAC104 in apple plants affected the accumulation pattern of osmoregulatory substances in the stem and leaves, and improved cold tolerance (Mei, 2023).
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