Molecular Plant Breeding 2025, Vol.16, No.3, 165-179 http://genbreedpublisher.com/index.php/mpb 169 4.2 Role of TFs in drought resistance TFs play a crucial role in mediating the plant’s response to drought stress. Several TF families, including bHLH, bZIP, NAC, and MYB, have been implicated in drought resistance. The bHLH TFs are significantly upregulated under drought conditions, enhancing stress tolerance (Soltanpour et al., 2022). OsbHLH148, in particular, interacts with JAZ proteins to activate jasmonic acid signaling, contributing to drought adaptation (Seo et al., 2011). The NF-YA TF OsNF-YA7 has been shown to confer drought tolerance in an ABA-independent manner by regulating downstream genes involved in drought response (Lee et al., 2015). Additionally, OsNF-YB1 positively affects drought tolerance by enhancing root architecture and promoting the expression of stress-responsive genes (Nelson et al., 2007). The TF, C2H2-type regulates stomatal closure in response to water deficit stress and is also responsible for inducing gene expression to quench ROS and H2O2, thereby maintaining their dynamic balance during drought stress (Huang et al., 2009). Moreover, Cominelli et al. (2005) reported that AtMYB60, a TF primarily expressed in guard cells, plays a key role in controlling the opening and closing of stomatal apertures as part of the plant’s drought tolerance responses. Similarly, the AP2/ERF TF OsERF71 alters root structure to enhance drought resistance by promoting cell wall loosening and lignin biosynthesis (Lee et al., 2016). The NAC TF ONAC022 and the MYB TF OsMYB6 also contribute to drought and salt stress tolerance by modulating ABA-mediated pathways and enhancing the expression of stress-responsive genes (Hong et al., 2016; Oladosu et al., 2019). Furthermore, OsMYB2 enhances proline accumulation and ROS scavenging, further improving rice drought resilience (Yang et al., 2012). Using an integrative approach combining a genome-wide association study with analyses of introgression lines and transcriptomic profiles, Sun et al. (2022) identified a gene DROT1, encoding a COBRA-like protein that confers drought resistance in upland rice. A C-to-T single-nucleotide variation in the promoter increases DROT1 expression and drought resistance in upland rice. DROT1 is specifically expressed in vascular bundles and is directly repressed by ERF3 and activated by ERF71, both drought-responsive TFs. 4.3 Signal transduction pathways involved in drought response Signal transduction pathways are essential for the activation of drought-responsive genes and for regulating rice’s adaptive mechanisms under water-limited conditions. The ABA signaling pathway is a key regulator of drought response in rice. The bZIP TF OsbZIP23 is activated by SAPK2, a SnRK2 protein kinase, and regulates a large number of genes involved in stress response and ABA biosynthesis and signaling (Zong et al., 2016). Other bZIP TFs, such as OsbZIP46, also regulate drought stress through ABA-dependent pathways (Tang et al., 2012). The AREB/ABF TFs, including AREB1, AREB2, and ABF3, are master regulators of ABA-dependent gene expression and are crucial for drought tolerance. These TFs require ABA for full activation and regulate the expression of LEA and PP2C genes, which are involved in stress response (Yoshida et al., 2010). Additionally, network-based machine-learning approaches have identified key TFs, such as OsbHLH148, that regulate stress signal transduction and modulate gene expression under drought conditions (Gupta et al., 2021). The molecular mechanisms of drought resistance in rice involve a complex interaction of gene regulation, TFs, and signal transduction pathways. Understanding these mechanisms provides a foundation for developing drought-resistant rice varieties through molecular breeding. 5 Genomic Approaches to Enhance Drought Resistance 5.1GWAS GWAS has emerged as a powerful tool for dissecting the genetic architecture of complex traits, including drought resistance in rice. By analyzing genetic variants across diverse rice populations, GWAS can identify loci associated with drought resistance traits. A study identified 470 association loci related to drought resistance, with 443 loci identified using image-based traits (i-traits) and 437 loci co-localizing with previously reported drought-related quantitative trait loci (QTLs) (Guo et al., 2018). Another study highlighted the identification of loci underlying tens of rice traits, including drought resistance, and emphasized the importance of functional characterization of candidate genes discovered through GWAS (Wang et al., 2011). Additionally, GWAS has been used to identify significant associations for root traits under drought stress, which are crucial for drought avoidance (Li et al., 2017).
RkJQdWJsaXNoZXIy MjQ4ODYzNA==