Potassium (K) is a critical macronutrient for sugarcane (Saccharum spp.), playing a vital role in metabolic processes, sucrose accumulation, and yield formation. Herein, this study systematically evaluated the effects of potassium oxide (K₂O) application on sugarcane (cultivar YZ1696) growth at the seedling and tillering stages. Hydroponic experiments demonstrated that 6 mmol/L K₂O optimally promoted seedling growth, whereas field trials revealed that 150 kg/ha K₂O maximized growth rate, yield, and sucrose content. Sugarcane growth exhibited a biphasic response—stimulation followed by inhibition—with increasing K₂O dosage at both developmental stages. Transcriptomic profiling of sugarcane roots under low-potassium (K-deficient), optimal potassium, and high-potassium conditions identified 10,266 differentially expressed genes (DEGs), with the most pronounced transcriptional shifts occurring under K deficiency. Functional enrichment analysis identified DEGs associated with potassium transport, calcium signaling, and carbohydrate metabolism. Notably, potassium uptake was mediated by distinct mechanisms: Shaker family channels (AKT1, AKT2, SPIKE) and the TPK family member KCO1 were induced under optimal K supply, whereas HAK/KUP/KT transporters (HAK1/5/10/21/25) exhibited broad activation across K concentrations, underscoring their key role in K homeostasis. Furthermore, calcium signaling genes (e.g., CIPK23) displayed K-dependent expression patterns. Weighted gene co-expression network analysis identified key gene modules that correlated strongly with agronomic traits, including plant height, yield, and sucrose content. Optimal K conditions favored the expression of yield- and sucrose-associated genes, suggesting a molecular basis for K-mediated productivity enhancement. Our findings revealed the genetic and physiological mechanisms underlying K-dependent sugarcane improvement, providing actionable insights for precise potassium fertilization to maximize the yield and sugar content.

Axillary bud germination in sugarcane is a critical agronomic trait that directly determines seedling emergence and tillering capacity; however, its molecular regulatory mechanisms remain poorly understood. In this study, we systematically investigated the hormonal dynamics and transcriptomic profiles of the sugarcane cultivar XTT22 across five developmental stages (from dormancy to the first new leaf stage). Our results revealed that abscisic acid (ABA) content fluctuated during germination, whereas indole-3-acetic acid (IAA) and gibberellin (GA) levels decreased significantly, suggesting their negative regulatory roles. In contrast, cytokinin (CTK) and ethylene (ETH) contents increased at the initiation stage, indicating positive promoting functions. Transcriptome analysis identified 31,513 differentially expressed genes (DEGs), which were significantly enriched in pathways related to hormone signal transduction, starch/sucrose metabolism, and photosynthesis. Weighted gene co-expression network analysis (WGCNA) constructed 12 co-expression modules, among which the antiquewhite4 module (negatively correlated with IAA, GA, and ABA contents) and the darkorange2 module (positively correlated with cytokinin content) were identified as key regulatory modules. From these modules, seven core hub transcription factors (e.g., ScTCP5, ScSCR, and ScSHR1) were screened, and their expression patterns were validated by RT-qPCR. Furthermore, the expression trends of six hormone-related DEGs were highly consistent with the RNA-seq data. Collectively, this study elucidates the hormonal dynamics and gene regulatory networks underlying axillary bud germination in sugarcane, providing candidate gene resources for breeding high-yield varieties with enhanced emergence and tillering capacity.