Cotton Genomics and Genetics 2025, Vol.16, No.6, 269-277 http://cropscipublisher.com/index.php/cgg 271 signal transduction, some for regulating transcription, and others contribute to osmotic protection, antioxidation, or maintaining cell membrane stability. However, to truly make a detailed classification, it is necessary to take into account their performance under different pressures. Figure 1 Subcellular localization of pCAMBIA2300-DsRED2-GhRF2-32fusion protein (Adopted from Gu et al., 2023) 3.2 Major stress types Among various environmental stresses, salinity, drought and low temperature pose the most challenges to cotton. Just talking about salt and drought, these two stresses are sufficient to cause the imbalance of water regulation and ion disorder in plants, ultimately leading to a decrease in yield (Kilwake et al., 2023). The problem of low temperatures is even more "insidious", especially during the emergence and seedling stages, when the damage to cotton often comes suddenly and severely. Although stresses such as high temperature, water accumulation and heavy metals also exist, the current research attention is still less than that of the former three. Although different types of stress have their own characteristics, they are not completely isolated at the gene expression level. The initiation of many stress response genes is crossed, showing certain commonalities or complementarities (Wang and Zhang, 2024). 3.3 The role of stress-responsive genes in stress tolerance Not all genes can be called "stress responses", but once they are included in this category, it usually means that they do play a key role in regulating cotton's resistance to external stress. Whether by initiating signal transduction or activating protective mechanisms (such as accumulating osmotic substances and enhancing antioxidant capacity), these genes are involved in regulating physiological states to help cotton "resist". Transcription factors such as DREB and bZIP are often regarded as signal "switches", while genes related to LEA protein and proline synthesis are more like "executors", providing support at the cellular level (Fang et al., 2025). Genes like these, once overexpressed or knocked down, will directly change the performance of cotton under stress such as salt, drought and cold, which also provides an operable target for subsequent breeding or molecular engineering (Guo et al., 2022). 4 The Impact of Promoter Variants on Cotton Stress-Responsive Gene Expression 4.1 Changes in transcription factor binding due to promoter variants Whether there are many cis control elements or not, and whether their positions are reliable or not, will actually change due to a small variation of the starter. Like GhNAC2, its promoter region is home to many components related to hormones and abiotic stress, and the corresponding hormones are also numerous - gibberellin, ethylene, auxin, abolic acid are all within the regulatory range, as well as stress factors such as mannitol and NaCl (Naresh et al., 2024). The combination of these components not only affects which transcription factors can bind, but also determines whether they are expressed in the leaves or activated at the root tips, and whether they respond to stress or remain low-key all the time. Another example is GhHSP70-26, whose promoter insertion deletion
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