Bioscience Methods 2025, Vol.16, No.1, 1-10 http://bioscipublisher.com/index.php/bm 3 encodes a vacuolar Na+/H+ antiporter, into sweet potato has demonstrated improved salt tolerance by enhancing Na+ compartmentalization into vacuoles, thus maintaining ionic homeostasis and reducing cellular damage. 2.3 Temperature stress (heat and cold) Sweet potato is also susceptible to temperature extremes, including both heat and cold stress. Heat stress can lead to protein denaturation and membrane instability, while cold stress can cause cellular damage and metabolic disruptions. The overexpression of the StnsLTP1 gene in transgenic potato plants has shown enhanced tolerance to heat stress by improving cell membrane integrity and activating antioxidative defense mechanisms (Gangadhar et al., 2016). Similarly, the overexpression of the SoBADH gene in sweet potato has been found to improve cold tolerance by increasing glycine betaine (GB) accumulation, which helps in maintaining cell membrane integrity and reducing ROS production (Fan et al., 2012). Additionally, the AtNHX1 gene has been shown to confer cold tolerance by enhancing ROS scavenging and maintaining cellular homeostasis (Fan et al., 2015). 2.4 Heavy metal toxicity Heavy metal toxicity, although less studied in sweet potato, poses a significant threat to plant health by inducing oxidative stress and disrupting cellular functions. The mechanisms of tolerance to heavy metals involve the activation of antioxidative defense systems and the sequestration of heavy metals into vacuoles. While specific studies on heavy metal tolerance in sweet potato are limited, the general principles of ROS scavenging and ion compartmentalization observed in other abiotic stresses are likely applicable. 3 Physiological Mechanisms of Abiotic Stress Tolerance in Sweet Potato 3.1 Water-use efficiency and stomatal regulation Water-use efficiency (WUE) and stomatal regulation are critical for sweet potato’s adaptation to abiotic stresses such as drought and salinity. The IbSnRK1 gene has been shown to play a significant role in controlling stomatal closure via the abscisic acid (ABA) signaling pathway, thereby enhancing drought and salt tolerance. Overexpression of IbSnRK1 in transgenic sweet potato plants resulted in increased ABA content and improved stomatal regulation, which are essential for maintaining water balance under stress conditions (Ren et al., 2020). Additionally, the non-tandem CCCH-type zinc-finger protein IbC3H18 regulates the expression of stress-responsive genes involved in stomatal closure, further contributing to enhanced water-use efficiency (Zhang et al., 2019). 3.2 Osmotic adjustment and ion homeostasis Osmotic adjustment and ion homeostasis are vital for sweet potato's resilience to abiotic stresses. The overexpression of the IbMIPS1 gene in sweet potato has been shown to enhance osmotic adjustment by increasing the levels of inositol, proline, and other osmolytes, which help maintain cell turgor and protect cellular structures under salt and drought stress (Zhai et al., 2016). Furthermore, the IbSnRK1 gene also contributes to ion homeostasis by increasing potassium (K+) content and reducing sodium (Na+) accumulation, thereby mitigating the detrimental effects of salt stress. The accumulation of glycine betaine (GB) through the overexpression of the SoBADH gene also aids in osmotic adjustment and ion homeostasis, enhancing the plant's tolerance to multiple abiotic stresses (Fan et al., 2012). 3.3 Antioxidant defense system The antioxidant defense system is crucial for scavenging reactive oxygen species (ROS) generated under abiotic stress conditions (Golldack et al., 2014). The IbBBX24-IbTOE3-IbPRX17 module has been identified as a key player in enhancing the antioxidant defense system in sweet potato. Overexpression of IbBBX24 and IbPRX17 leads to increased peroxidase activity and reduced H2O2 accumulation, thereby improving tolerance to salt and drought stresses (Zhang et al., 2021). Similarly, the IbSnRK1 gene enhances the activities of ROS-scavenging enzymes, such as superoxide dismutase (SOD) and catalase (CAT), which are essential for mitigating oxidative damage (Figure 2). The overexpression of the IbC3H18 gene also upregulates genes involved in the ROS scavenging system, further bolstering the plant's antioxidant defenses.
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