Molecular Plant Breeding 2024, Vol.15, No.3, 90-99 http://genbreedpublisher.com/index.php/mpb 94 High temperature stress occurs when the ambient temperature reaches or exceeds the maximum temperature threshold for plant growth. This stress may lead to problems such as reduced photosynthetic efficiency, altered protein structure, and increased membrane lipid peroxidation in plants, which in turn affects flowering and fruiting and may cause tissue damage, such as standing wilt in seedlings. It has been found that in response to high-temperature stress, plants synthesize heat-stimulated proteins (HSPs), which are usually regulated by heat-stimulated transcription factors (HSFs). NAC019 overexpressed in Arabidopsis thaliana was able to bind to the promoters of HSFA1b, HSFA6b, HSFA7a, and HSFC1, increasing the heat tolerance of plants (Guan et al., 2014). Under high-temperature treatment, by transferring the TaNAC2 gene from wheat to Arabidopsis, the hypocotyl growth length of transgenic TaNAC2L Arabidopsis significantly exceeded that of wild-type plants, and expression levels of six thermally induced genes in Arabidopsis notably surpassed those in the wild type, implying that TaNAC2L enhances thermal resistance by orchestrating the expression of stress-related genes (Guo et al., 2015). When overexpressed in transgenic Arabidopsis, ZmNAC074 isolated from corn significantly enhances plant tolerance to high-temperature environments by regulating various stress metabolites such as reactive oxygen species (ROS), malondialdehyde (MDA), proline, soluble protein, chlorophyll, and carotenoids (Xi et al., 2022). The involvement of NAC transcription factors can appropriately regulate the mechanism of plant response to temperature stress, helping plants to adapt and resist these adverse environmental factors to a certain extent. In addition, ATAF1 in Arabidopsis thaliana is negatively regulated under high-temperature environment. ATAF1 knockout mutants exhibited better heat tolerance compared to the wild type in the experiment (Alshareef et al., 2022). 3.4 Heavy metal stress Heavy metal stress refers to the presence of heavy metal ions in the environment, such as Cd Mn, Pb, Cd, and Hg, etc, present in the environment at too high a concentration, negatively affect organisms (especially plants). When these heavy metal ions enter the plant body, they interfere with normal physiological and biochemical processes and induce a series of defense responses. Research has found that NAC transcription factors fromAegilops markkrafii can reduce cadmium concentration in transgenic wheat. Under excessive cadmium treatment, the transcription of AemNAC2 and AemNAC3 is upregulated approximately 150 times, Overexpression of AemNAC2 in the wheat variety "Bobwhite" leads to a decrease in cadmium concentration in roots, aboveground parts, and grains (Du et al., 2020). In addition, IDEF2 (Iron deficiency responsive cis acting element 2) in the rice NAC family can maintain Fe stability in rice tissues (Walker and Connolly, 2008). Another study found that SiNACs in willows exhibit two significant Pb positive reaction patterns (early and late), both containing 10 SiNACs (Xin et al., 2023). In addition, Overexpression of TdNAC8470 in rice increased grain starch concentration but decreased grain Fe The content of Zn and Mn may be involved in regulating grain protein content, starch synthesis, etc. (Gong et al., 2022). 3.5Others In addition to the aforementioned abiotic stresses, plants may also face mineral nutrient stress, light stress, oxidative stress, and mechanical and physical damage. For example, research has found that after dark treatment, more than 1/4 of NAC expression is increased in Arabidopsis leaves (Lin and Wu, 2004); And under strong light, ANAC078 can induce genes related to flavonoid biosynthesis, increase the accumulation of anthocyanins, and cope with high light stress (Morishita et al., 2009). At 0.1% oxygen, the decrease in ANAC102 expression significantly reduces germination efficiency, but the increase in expression has no effect on germination. Arabidopsis ANAC102 is an important regulatory factor for seed germination under flooded conditions (Christianson et al., 2009). Under low phosphorus stress, soybean transcription factor GsNAC1 can regulate the expression of genes in plant roots, stems, and leaves, enhancing soybean tolerance to low phosphorus soil (Xiong et al., 2024).
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