Rice Genomics and Genetics 2025, Vol.16, No.4, 219-236 http://cropscipublisher.com/index.php/rgg 233 practices and modern molecular methods. Looking ahead, we should guide the cultivation of high-quality rice varieties with a systems perspective: we should not only leverage the power of metabolic engineering improvement in the starch synthesis pathway, but also attach importance to field trials and the control of comprehensive traits through traditional methods. Only by taking a three-in-one approach of "molecular design + conventional improvement + optimized cultivation" can the high-quality genes in the laboratory be truly transformed into practical achievements such as increased field yields, enhanced aroma in rice buckets, and enhanced flavors on dining tables (Zhong et al., 2023). 7 Concluding Remarks In recent years, functional genomics and gene editing technologies have developed rapidly. People's understanding of the starch synthesis pathway in rice is also deeper than before. New regulatory factors and metabolic mechanisms are constantly being discovered, which makes the original regulatory network more complete. In the field of genetic research, scientists have identified many new genes and alleles that affect starch synthesis. For instance, Du and flo genes that regulate amylose, as well as long-chain sucrose transporters that affect the structure of amylopectin, etc. All of these were determined through mutant cloning methods. These achievements have made us more clearly aware that the regulation of starch synthesis is extremely complex. In terms of trait inheritance, people have gained a clearer understanding of the quantitative genetic basis of starch quality. By using genome-wide association analysis (GWAS) and genome-wide selection, researchers have elucidated the genetic structures of important traits such as amylose content, gel consistency, and chalkiness rate, and have also identified many new quantitative regulatory loci. For instance, Indian scientists analyzed 3,000 core germplasms and identified 11 key loci related to resistant starch and predicted glycemic index, providing a reference target for improving low-GI rice. In terms of regulatory mechanisms, the roles of epigenetics and non-coding Rnas have attracted increasing attention. New sequencing techniques have mapped out the specific methylation map of endosperm and long non-coding RNA lineages. Although their specific functions still need further research, these results have already suggested that there may be more levels in the regulation of starch synthesis. In the field of synthetic biology, there have also been notable advancements. A Chinese research team has for the first time achieved the artificial synthesis of starch in vitro, converting CO2 into starch molecules in one step. Although this method cannot be implemented in plants at present, it theoretically offers new possibilities for the future modification or reconstruction of crop starch synthesis pathways through metabolic engineering. Although there have been many advancements in the research on the regulation of rice starch synthesis, there are still some unsolved problems. First, the basic mechanism is still not clear enough. In the starch synthesis pathway, how different key enzymes assemble into complexes on the particle surface and work together is currently only speculated by models, and there is no direct evidence yet. To understand this issue, more advanced in-situ analysis techniques are needed. Second, there is insufficient understanding of the signal regulation of endosperm development. We know that the hormones and nutritional signals of plants can affect starch accumulation, but the specific process is still unclear. For instance, it is not yet fully understood how they function through the transcription factor network or by regulating enzyme activity. For instance, it is still unclear which signaling pathways will inhibit the expression of the amylase gene under high-temperature stress. Thirdly, it is difficult to balance output and quality. In breeding, many mutations that can improve the quality of rice can lead to a decrease in yield. Varieties with high amylose or high resistant starch are often accompanied by a decrease in 1000-grain weight and insufficient grain filling. How to break this negative correlation and achieve both high quality and high yield still requires new ideas. Perhaps the traits of different mechanisms can be combined, such as enhancing the grain filling strength while improving starch, but there are still few successful cases in this regard. Fourth, the quality standards are not uniform. Consumers' demands vary greatly and are subjective. It cannot be measured by a single indicator. The improvement of main parameters such as amylose has been relatively mature, but the sensory properties of rice, such as aroma, texture and graininess, are more complex, and the involved components and related genes are still not clear enough. Fifth, there are difficulties in promoting the technology. The potential of gene editing is great, but it is currently difficult and costly to stably edit multiple gene loci at one time in crops. For instance, the efficiency of editing more than three sites at once is not high, and the homozygous screening of
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