Rice Genomics and Genetics 2025, Vol.16, No.2, 86-95 http://cropscipublisher.com/index.php/rgg 87 As for why it is like this, the mechanism behind it is not simple. It is known that it involves multiple levels of regulation, such as the expression of specific genes, and the role played by non-coding RNA and miRNA (Zhou et al., 2012; Sun et al., 2021). This review focuses on the gene OsTms6, which is closely related to the TGMS trait. We will sort out its role and regulation from multiple perspectives, including genetics, molecular mechanisms, and breeding practices. Understanding the function of OsTms6 is not only to understand how it makes rice "infertile", but also to use this knowledge to cultivate hybrid rice varieties that are more adaptable to the climate and have higher yields, providing a more reliable foundation for food security. 2 Identification and Cloning of OsTms6 2.1 Discovery of OsTms6 In hybrid rice breeding research, the exploration of temperature-sensitive male sterility has never stopped. What really attracted widespread attention was a special phenomenon observed in the new TGMS line G20S: as long as the temperature is below 29.5 °C, this material shows the characteristics of complete sterility (Liu et al., 2010). This was quickly noticed by breeders because it meant that it could adapt to more Asian climates. Later, through genetic analysis, researchers confirmed that this sterility was controlled by a recessive gene, temporarily named tms6(t) (Liu et al., 2010). However, G20S is not the only example. In fact, as early as in South Korea, a spontaneous mutant japonica rice material called Sokcho MS was also found to have similar traits (Lee et al., 2005). The TGMS gene it carries is also named tms6 and is located on the long arm of chromosome 5. The two systems are independent but point to the same gene, which undoubtedly strengthens people's understanding of the importance of OsTms6 in TGMS research. 2.2 Cloning technology used It is not easy to locate a gene, but the researchers tried many methods and finally successfully cloned OsTms6. In the G20S study, they first used SSR markers to perform batch segregation analysis and screened out some markers that may be related to tms6(t). Further co-segregation analysis identified two closely linked markers, RM3152 and RM4455, which allowed the researchers to accurately locate the gene on chromosome 10 (Liu et al., 2010). The situation is slightly different in Sokcho MS. The research there combined SSR, STS and EST markers, and the positioning work was more detailed, and finally narrowed the target area to between RM3351 and E60663 on chromosome 5 (Lee et al., 2005; Yang et al., 2006). Although the research ideas are different, the results provide precise "coordinates" for the subsequent cloning of OsTms6. 2.3 Verification of OsTms6 as aTMSgene Location alone is not enough, and verifying its function is the key. On the G20S material, the researchers conducted a complementary experiment. They selected a 2.4-kb DNA fragment containing the wild-type tms6(t) allele and introduced it into the sterile plants. As a result, pollen fertility was restored, which basically confirmed the role of tms6(t) in TGMS (Liu et al., 2010; Pan et al., 2014). The verification method of Sokcho MS is not so direct, but it is also very convincing. The genetic analysis there also showed that sterility is controlled by a recessive gene, and the positioning results showed that this tms6 is not any previously known TGMS gene, but a new one (Lee et al., 2005). This makes people further realize that OsTms6 is not a phenomenon unique to a single material, but a gene with universal significance. In general, although these works come from different research groups and use different research materials, they ultimately converge on the same gene point - OsTms6. Its discovery, cloning and verification not only give us a clearer understanding of rice temperature-sensitive sterility, but also provide more possibilities for breeding work.
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