The establishment of an efficient symbiotic relationship between soybean and rhizobia requires precise regulation of root nodule development. While sugar transporters are known to participate in nutrient allocation during symbiosis, their molecular functions and regulatory mechanisms in this process remain poorly characterized. This study aims to functionally characterize the sugar transporter GmSWEET17 and elucidate its role in soybean-rhizobia symbiosis. Building upon initial yeast library screening that identified GmSWEET17 as a novel interacting partner of the Nod factor receptor GmNFR1α, this study further confirmed their physical interaction through yeast two-hybrid assays and luciferase complementation imaging (LCI) in tobacco leaves. The two proteins were shown to co-localize at the plasma membrane in Arabidopsis mesophyll protoplasts. Rhizobial infection induced GmSWEET17 expression in roots, with dynamic expression patterns showing an initial increase followed by a decrease during nodule development. Promoter activity assays demonstrated specific expression of GmSWEET17 in the vascular tissues of roots and nodules. Heterologous expression in yeast revealed that GmSWEET17 primarily transports glucose. Overexpression of GmSWEET17 in transgenic hairy roots led to reduced nodule number but increased nodule size and enhanced nitrogen fixation activity. Furthermore, GmSWEET17 overexpression up-regulated the expression of key nodulation marker genes. Our results demonstrate that GmSWEET17, a sugar transporter interacting with GmNFR1α, positively regulates soybean nodule development and nitrogen fixation efficiency. This study provides new molecular evidence for the biological function of GmSWEET17 in nodulation and nitrogen fixation, and offers novel insights into the regulatory mechanisms of GmNFR1α in rhizobial symbiosis.
Ke et al. (Thu,) studied this question.
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