The sugar transporter (STP) gene family is a key regulator of plant development, which is crucial for the efficient transport and utilization of sugars during plant growth and development. In this study, we identified the MeSTP7 gene, which is highly expressed in cassava fibrous roots, early storage roots, and under hormonal treatment, including IAA, MeJA, ABA, and GA₃, and abiotic stressors, such as mannitol and NaCl. A strong response was observed with exoqenous IAA. Transfecting MeSTP7 into Arabidopsis promoted early seedling growth, particularly in lateral root development. The content of endogenous hormones (IAA and MeJA) as well as soluble sugars (sucrose, fructose, and glucose) was elevated in transgenic Arabidopsis. Hormone treatments with IAA, MeJA, GA₃, and ABA on transgenic Arabidopsis revealed that transgenic Arabidopsis responded positively to added 20 μM IAA. They also exhibited co-induced regulation of lateral root formation by GA₃, MeJA, and ABA. qRT-PCR analysis showed that overexpression of MeSTP7 upregulated the expression of IAA14, ARF7, and ARF19 in Arabidopsis. Under IAA treatment, the expression of these genes was similarly upregulated but downregulated under MeJA treatment. These results suggest that MeSTP7 may promote Arabidopsis seedling development by increasing the content of sucrose, glucose, and fructose in roots, which in turn influences IAA-based hormonal signaling.

To characterize the trends in the fermentation weight loss (FWL), nutrient composition, and fermentation quality of king grass silage under different ensiling temperatures and storage periods, chopped and wilted king grass was ensiled at 15 °C, 20 °C, 25 °C, 30 °C and 35 °C for 7, 30, 60 and 120 days, respectively. Nutritional and fermentation-related parameters were predicted by near-infrared reflectance spectroscopy (NIRS) using the general Dairy One forage database. FWL was determined gravimetrically, and correlation and cluster analyses were performed for comprehensive data evaluation. The results showed that ensiling temperature, storage period, and their interaction significantly affected the FWL, nutrient composition (except for the soluble protein-to-crude protein ratio, SP/CP), and fermentation quality (except for the butyric acid, BA) of king grass silage (p < 0.05). FWL tended to increase with rising temperature and prolonged ensiling duration. With extended ensiling time, NIRS-predicted acid detergent fiber (ADF), neutral detergent fiber (NDF), ash, BA, ammonia, and SP/CP exhibited increasing trends. By contrast, NIRS-predicted dry matter, water-soluble carbohydrates (WSCs) and pH decreased significantly from day 7 to day 30 (p < 0.05). The 15 °C treatment favored the preservation of NIRS-predicted WSCs and crude protein over long-term ensiling (120 d). The NIRS-predicted ammonia under 25 °C remained at a relatively low level across the whole ensiling period; lactic acid was highest at days 7 and 60, whereas no significant difference was observed among temperatures at day 120 (p > 0.05). Both low temperature (15 °C) and high temperature (35 °C) were unfavorable for rapid pH decline. At most sampling time points, NIRS-predicted ADF and NDF contents under 30 °C and 35 °C were significantly higher than those under 15 °C (p < 0.05). Correlation analysis showed that ADF, NDF, ash, ammonia, and BA were positively correlated with each other; WSCs were negatively correlated with SP/CP, ADF, NDF, ash and acetic acid but positively correlated with pH and the lactic acid-to-acetic acid ratio. Cluster analysis classified the 13 silage quality indicators into three clusters and the 60 treatment samples into five clusters. This work offers preliminary references for developing differentiated king-grass-ensiling strategies adapted to diverse climatic regions.