Cotton Genomics and Genetics 2025, Vol.16, No.5, 232-240 http://cropscipublisher.com/index.php/cgg 237 be released, resulting in more favorable fiber extension (Kwak et al., 2009). Similarly, miR828 targets the MYB gene related to hair and fiber development, and the logic is similar. So, if certain circrnas "intervene" at critical moments, they may be able to influence the expression of these developmental regulatory factors, ultimately affecting the quality and yield of cotton fibers. 6.3 Functional validation and phenotypic consequences in overexpression/knockdown lines Not all speculations are reliable; experiments have to speak for themselves. Take miR156/157 as an example. Experiments have shown that if its function is artificially inhibited, the length of cotton fibers will significantly shorten, which is sufficient to demonstrate their importance in fiber elongation (Figure 2) (Liu et al., 2014). However, it should be noted that there are currently few studies on the overexpression or knockdown of specific circrnas directly in cotton fiber cells. The evidence in this regard is indeed insufficient. However, the existing results of ceRNA network construction and the phenotypic changes after miRNA functional intervention are actually suggesting that circRNA's regulation of miRNA through "spongization" may have a substantial impact on the developmental process. Next, if the levels of circRNA can be further controlled through transgenic technology, perhaps their true "weight" in the development of cotton fibers can be more clearly defined. 7 Biotechnological and Breeding Implications of circRNAs in Cotton 7.1 Potential of circRNAs as novel molecular markers or regulatory targets Finding suitable molecular markers in cotton breeding has always been an old problem. Although traditional marking techniques are mature, they are sometimes not precise enough, especially when dealing with complex traits. Now, circRNA has begun to come into the view of researchers, and the reasons are not complicated: it is stable, not easily degraded, and the amount expressed in which tissue and at which developmental stage varies significantly. It is precisely these characteristics that have led people to start considering-could circRNA be regarded as a new type of marker candidate? Especially during key processes such as drought stress or fiber formation, the expression patterns of some circrnas will change significantly (Zhang et al., 2024), which undoubtedly opens up new ideas for screening related agronomic traits. Furthermore, it is not merely a "mark". Some circrnas can also adsorb mirnas, thereby affecting gene expression, which indicates that they themselves have regulatory value. If those circrnas related to agronomic traits and conserved in multiple cotton varieties can be identified, perhaps they can also serve as targets and directly participate in breeding design. 7.2 Engineering circRNA expression for improving fiber quality or stress resistance Not all circrnas are useful, but some of them are indeed "well-managed". Circrnas that can bind to mirnas and happen to occur in fibrous development or adverse response have become potential intervention targets. Through genetic engineering methods, such as overexpressing a certain circRNA or knocking it down-it is possible for us to indirectly regulate the activity of miRNA and further regulate those genes related to development or resistance (Li et al., 2023). For instance, some studies have mentioned that regulating the circRNA network related to drought response might be a strategy to enhance the stress resistance of cotton. Of course, this method is not intended to completely replace traditional breeding. It is more like a "reinforcement": on the basis of the existing genetic background, it fine-tunes key regulatory points to enhance specific traits, rather than redesigning the entire cotton plant. 7.3 Integration of circRNA knowledge into precision cotton breeding strategies Introducing circRNA into the precision breeding system may sound complicated, but the logic is actually very simple. High-throughput sequencing has already been able to help us identify which circrnas are highly expressed in good varieties and which ones are closely related to stress responses. The next thing is how to make good use of this information. The existing plant circRNA database is currently expanding. Once sufficient resources are accumulated, breeders can fully transform this information into practical operations, such as designing molecular marker-assisted selection programs or directly conducting genome editing at circRNA sites (Zhu and Luo, 2024). The ultimate goal is not to create a gimmick, but to screen out genotypes with more efficient regulatory networks and better trait expression. However, now there is a new perspective-no longer just looking at linear genes, but also beginning to pay attention to those RNAs that have gone in a "circle".
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