Cotton Genomics and Genetics 2025, Vol.16, No.4, 163-172 http://cropscipublisher.com/index.php/cgg 165 However, these genes don't actually take the lead; they often simply "execute tasks." The timing and quantity of cellulose synthesis are orchestrated by MYB family genes like GhMYB7 and GhMYBL1 (Huang et al., 2021). However, MYB genes themselves are not always stable. Sometimes, when their rhythm is disrupted, the underlying CesA gene can malfunction: either causing unstoppable fiber growth or causing extremely thin cell walls, ultimately affecting the overall fiber quality (Wang et al., 2023b). So, while CesA genes play a significant role in cellulose synthesis, they are essentially under orders and cannot act on their own. Ultimately, fiber quality depends on the coordination of this regulatory system. Figure 1 Schematic model of the evolutionary history of diploid and allotetraploid cotton (Adapted from Han et al., 2022) 3.2 Expansin gene family In addition to cellulose, another class of "supporting forces" plays a crucial role in the elongation phase: expansins. These proteins' job is straightforward: loosen the cell wall to allow the cell to expand outward. Ninety-three related genes have been identified in cotton, but not all of them are always on call. Some, such as GhEXPA4a and GhEXPA13a, are particularly explosive during the rapid elongation phase (Lv et al., 2020); others, on the other hand, either come on early or quietly "come online" once the cell wall begins to thicken. They aren't always online, but as soon as their expression levels rise, the "jointing" stretching state of the cell often occurs, indicating that they play a role in regulating elongation. 3.3 MYB transcription factors How do cotton fibers grow? Simply put, it's a group of genes that rotate in and perform their respective roles. The MYB gene family is particularly active within this group, controlling key processes. For example, some members are busy promoting cellulose synthesis, while others participate in fatty acid production, both of which are crucial for fiber structure (Suo et al., 2024). However, not every member works equally hard. GhMYB7 and GhMYB25 (Wu et al., 2018) are very active, often working on the front lines to spur the CesA genes to work. Meanwhile, GhMYB4 is more passive, slowing fiber growth and being considered a "speed reducer" (Duan et al., 2024). While one might imagine these opposing genes fighting, they don't. Instead, they appear at different times and don't interfere with each other. While these genes appear to have distinct personalities, they actually work in perfect harmony. It's this orderly rotation that allows for smooth fiber development. What may seem contradictory is actually the result of coordinated cooperation.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==