International Journal of Horticulture, 2025, Vol.15, No.5, 218-233 http://hortherbpublisher.com/index.php/ijh 225 WRKY, and bHLH are also involved in multiple pathways related to sugarcane quality. For example, ERF factors mediate ethylene signals, which can indirectly affect the expression of cell wall softening enzymes and defense enzymes; WRKY and bHLH regulate carbon allocation in response to adverse stress, which may change the accumulation pattern of sucrose and fiber (Khan et al., 2023). Transcription factors provide a powerful molecular tool for improving the sweetness and texture of sugarcane at the same time. By adjusting the activity of these factors through genetic engineering or molecular design breeding, it is theoretically possible to achieve synchronous regulation of multiple downstream structural genes, thereby synergistically optimizing complex traits. 4.3 Differential gene expression between sweet-crisp and fibrous cultivars The differences in sweetness and texture between fresh sugarcane varieties ultimately stem from differences in metabolic pathways and regulatory networks caused by genotype differences. High-sugar varieties often carry favorable allele combinations, which enable them to assimilate and accumulate sugar more efficiently under the same environment; accordingly, some genes of these varieties (such as SPS, SuSy, and sucrose transporter genes) may be more strongly expressed than ordinary varieties, allowing more photosynthetic carbon to flow to the sucrose pool (Niu et al., 2019). Conversely, some varieties with coarse and hard fibers may show higher basal expression levels in genes of the cell wall synthesis pathway, or have genetic mutations that make cell walls difficult to degrade, such as more active promoters of lignin monomer synthesis genes. Modern omics technologies provide a means to reveal these varietal differences. Transcriptome comparison can screen genes that are specifically upregulated in varieties with soft taste and genes that are highly expressed in varieties with coarse and hard fibers. Although there are not many reports on comparative transcriptome studies on the taste of fresh sugarcane, we can infer some possible conclusions from relevant studies: for example, sugarcane varieties with a tender and crisp taste may up-regulate the expression of some cell wall relaxants (such as expansins, XTH) and sucrose transporters, and down-regulate some lignin and fiber synthesis-related genes; on the contrary, varieties with coarser fibers have the opposite expression trend of these genes. Perlo et al. (2022) conducted a large-scale transcriptome analysis of 24 sugarcane varieties and found that the variation in gene expression patterns was closely related to the genotype, even exceeding the influence of the developmental stage. This shows that the differences in gene regulation of different varieties will cause them to present different metabolic states at the same developmental stage. This has been confirmed in the comparison of high-sugar and low-sugar varieties: high-sugar varieties maintain higher sucrose synthase activity and lower invertase activity throughout the growth period, making their sugar accumulation rate always faster than that of low-sugar varieties. Similarly, we have reason to believe that high-quality fresh sugarcane varieties may be born with certain favorable gene regulation characteristics, such as weaker lignification or stronger sugar redistribution ability, which makes them both sweet and soft. These differences can be explored through genomic and transcriptomic methods. For example, transcriptome comparison of several representative sugarcane varieties and common sugarcane varieties, or the use of genome-wide association analysis (GWAS) to find gene loci associated with sweetness and texture in natural germplasm will help to clarify the molecular basis of differences between varieties and provide targets for molecular breeding (Mehdi et al., 2024a). 5 Hormonal and Environmental Regulation 5.1 Impact of auxin and gibberellin on sucrose metabolism Auxin (IAA) and gibberellin (GA) are two key hormones that regulate plant growth and development. They not only determine the height and internode elongation of sugarcane, but also affect the distribution of carbohydrates in the body through complex signaling pathways (Khan et al., 2023). Auxin is present in high levels in young tissues and can promote cell elongation and division. It also induces source-sink conversion, causing more photosynthetic products to be consumed by fast-growing parts, which may reduce the allocation of sugar storage to the stem to a certain extent. This is considered to be one of the reasons why plants accumulate sugar slowly during the peak growth period. However, there is a two-way "dialogue" relationship between auxin and sucrose metabolism: sucrose itself can act as a signal to regulate the expression of genes related to the auxin pathway, such
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