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 <i>MeSTP7</i> 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 <i>MeSTP7</i> into <i>Arabidopsis</i> 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 <i>Arabidopsis</i>. Hormone treatments with IAA, MeJA, GA₃, and ABA on transgenic <i>Arabidopsis</i> revealed that transgenic <i>Arabidopsis</i> 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 <i>MeSTP7</i> upregulated the expression of <i>IAA14</i>, <i>ARF7</i>, and <i>ARF19</i> in <i>Arabidopsis</i>. Under IAA treatment, the expression of these genes was similarly upregulated but downregulated under MeJA treatment. These results suggest that <i>MeSTP7</i> may promote <i>Arabidopsis</i> seedling development by increasing the content of sucrose, glucose, and fructose in roots, which in turn influences IAA-based hormonal signaling.