Molecular Plant Breeding 2024, Vol.15, No.6, 351-361 http://genbreedpublisher.com/index.php/mpb 355 5.3 Role of transcription factors and other regulatory elements Transcription factors are central to the regulation of stress responses in sweet potato. They act as master regulators that control the expression of a wide array of genes involved in stress tolerance. For instance, the NAC transcription factor IbNAC3 has been identified as a key player in modulating the plant's response to combined salt and drought stresses. It activates the expression of downstream target genes and interacts with other NAC TFs to enhance stress tolerance (Figure 2) (Meng et al., 2022). Similarly, the WRKY transcription factor ItfWRKY70 has been shown to confer drought tolerance by regulating ABA biosynthesis, stomatal aperture, and the ROS scavenging system (Sun et al., 2022). In addition to TFs, other regulatory elements such as miRNAs also play significant roles in stress adaptation. miRNAs regulate gene expression at the post-transcriptional level by targeting mRNAs for degradation or translational repression. For example, miRNAs have been shown to modulate the expression of genes involved in salt stress response, thereby contributing to the plant’s overall stress tolerance (Yang et al., 2020). Figure 2 IbNAC3 cooperates with ANAC072 and NAP with a synergistic effect on transcriptional activation (Adopted from Meng et al., 2022) Image caption: (A) Heatmap showing hierarchical clustering of ChIP-seq peaks comparing transgenic and WT plants, indicating upregulated (red) and downregulated (blue) regions bound by IbNAC3. Plants were immunoprecipitated with an anti-Flag antibody, and the DNA-protein complexes were analyzed. (B) Schematics of AtCHX25, AtRH33, and MREL57 gene structures, highlighting core NACRS regions (red and blue) and exons (green), with distances from the ATG start codon marked. (C) ChIP-qPCR assays showing in vivo binding of IbNAC3 to the promoters of target genes, with significant enrichment compared to the WT. (D) Yeast one-hybrid assays confirming the physical interaction between IbNAC3 and the promoters of AtCHX25, AtRH33, and MREL57, validated on selective media. (E) Electrophoretic mobility shift assay (EMSA) illustrating in vitro binding of purified IbNAC3 to the promoters, showing specific DNA-protein complexes. (F) Diagrams of dual-luciferase reporter (DLR) constructs, showing promoters cloned into the reporter vector and effector constructs of IbNAC3, ANAC072, and NAP. (G) Transactivation assay results demonstrating that IbNAC3 activates transcription of the target promoters in Nicotiana benthamiana, as indicated by increased LUC/REN ratios. (H) Synergistic interaction between IbNAC3 and ANAC072/NAP further enhances the transactivation activity of the target gene promoters, with statistical analyses supporting significant interactions (Adapted from Meng et al., 2022)
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