Overexpression of Cassava MeSTP7 Promotes Arabidopsis Seedling Development

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.