International Journal of Horticulture, 2025, Vol.15, No.5, 218-233 http://hortherbpublisher.com/index.php/ijh 231 higher than that in the cultivated species (Zhang et al., 2018). Due to multiple generations of breeding, the transcriptome characteristics of modern sugarcane varieties tend to be more "high sugar and low fiber" gene expression profiles, that is, more similar to the ancestors of cultivated species. By constructing sugarcane whole genome databases and transcriptome databases, researchers are gradually mapping gene network maps related to quality. This will provide a basis for the precise improvement of fresh sugarcane. For example, if it is known that the transcription factor A specifically expressed in a high-quality variety can simultaneously upregulate sucrose synthesis genes and downregulate lignin synthesis genes, then by molecular means to increase the expression of A in other varieties, it is expected to replicate its quality traits. Using multi-omics comparative analysis of the differences between high-quality fresh sugarcane varieties and ordinary varieties and wild species, a group of key genes that determine sweetness and texture can be identified, which will point out the direction for future molecular design breeding. 7 Concluding Remarks The formation of sweetness and texture quality of fresh sugarcane stems is the result of the comprehensive effect of multi-level regulation. On the one hand, sucrose synthase, decomposition enzyme and transporter in the sugar metabolism pathway jointly determine the accumulation rate and upper limit of soluble sugar in stem cells; on the other hand, cell wall biosynthesis and modification enzyme system determine the amount and toughness of fiber. The two are both independent and mutually influential during the development process, and achieve dynamic balance through a complex signal network. High sweetness often means that the plant diverts more carbohydrates to the sucrose pool instead of building new cell walls, while a softer texture means appropriate adjustment of cell wall components and structures, such as reducing lignin and optimizing the fiber-colloid ratio. Fresh sugarcane varieties that can take into account both sweetness and softness are masterpieces of the above-mentioned mechanism of balanced regulation: they have an efficient sugar synthesis and transportation system and moderately "relax" the degree of cell wall reinforcement. In this balance, a series of signal and transcription regulatory factors play a key role, including feedback mechanisms mediated by sugar signals, the effects of hormones such as auxin/ethylene, and the overall coordination of transcription factors such as NAC and bZIP. Research in recent years has begun to reveal some unique regulatory mechanisms in sugarcane, such as sucrose affecting its own accumulation through uORF regulation of transcription factor ScbZIP44, and different co-expressed gene modules corresponding to two opposite traits of high sugar and high fiber. These findings provide a theoretical basis for a deeper understanding of the intrinsic relationship between sweetness and texture formation. The cultivation of high-quality fresh sugarcane needs to be guided by the above-mentioned mechanism research. In traditional breeding, it is often necessary to balance many traits. For example, increasing the sugar content may cause the stem to become fragile and the yield to decrease. Therefore, only by deeply understanding the biological basis of sweetness and texture can we break the constraint of negative correlation of traits and realize the breeding of "double-excellent" varieties. Sugar metabolism enzymes, cell wall components and regulatory genes provide rich targets for future molecular breeding. For example, it is possible to consider using genetic engineering to overexpress SPS or inhibit invertase to increase sucrose accumulation; at the same time, moderately downregulate lignin synthesis genes (such as COMT) through gene editing to soften the fiber. Such a combination of measures is expected to breed new "sweeter and softer" varieties. In practical applications, marker-assisted selection should also be combined to aggregate high-sugar and low-fiber gene alleles into the same variety. Breakthroughs in sugarcane genome sequencing and map construction in recent years have created conditions for this. In particular, the multi-omics data of sugarcane has gradually become rich, and the analysis of traits aggregated by multiple genes has become possible. By integrating genomic, transcriptomic, and metabolomic data, researchers can accurately locate the key gene loci that affect sweetness and texture, and make precise improvements through technologies such as gene editing.
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