Molecular Plant Breeding 2025, Vol.16, No.1, 73-81 http://genbreedpublisher.com/index.php/mpb 77 by increasing ABA and proline content, and activating the ROS scavenging system. The suppression of StHAB1, a negative regulator of ABA signaling, also enhances drought tolerance by increasing ABA sensitivity (Liu et al., 2023). These findings underscore the importance of ABA pathways in modulating drought responses in sweet potato. 5.3 Transcription factors and their influence on drought tolerance Transcription factors (TFs) are critical regulators of gene expression in response to drought stress. The WRKY family, particularly ItfWRKY70, has been shown to play a significant role in enhancing drought tolerance by regulating ABA biosynthesis and stress-response genes (Figure 3) (Sun et al., 2022). Another important group of TFs is the MYB family, including MYB33, MYB65, and MYB101, which regulate the ABA signaling pathway. Overexpression of these MYB TFs in transgenic plants leads to increased ABA sensitivity and improved drought tolerance (Wyrzykowska et al., 2021). Furthermore, the bHLH transcription factors, IbbHLH66 and IbbHLH118, have opposing roles in the ABA-mediated drought response, with IbbHLH66 enhancing and IbbHLH118 reducing drought tolerance (Xue et al., 2022). These TFs are crucial for fine-tuning the plant's response to drought stress, making them valuable targets for molecular breeding programs aimed at improving drought resistance in sweet potato. Figure 3 Responses of transgenic and WT sweet potato plants grown in a transplanting box with no stress (normal) and drought stress (Adopted from Sun et al., 2022)) Image caption: (a) Phenotypes, FW and DW, (b) ABA content, (c) Proline content, (d) SOD activity, (e) POD activity, (f) MDA content, (g) H2O2 content. The phenotypes are shown after drought treatment for 6 weeks. FW, fresh weight; DW, dry weight. Data are presented as the means ± SE (n=3) (Adopted from Sun et al., 2022)
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