Functional roles of miR862b in regulating soybean resistance to Heterodera glycines

The legume-specific miR862b, acting via targets such as GmGRX1, is associated with soybean responses to Heterodera glycines. Exogenous ds-miR862b reduces SCN root infection while moderately and transiently suppressing seed germination and early seedling growth. Soybean cyst nematode (SCN) disease has emerged as a significant threat to soybean production globally, causing substantial yield losses. Identifying key resistance molecular determinants is essential for enhancing soybean resistance to SCN. Previous studies have shown that miR862b exhibits a strong response in the early stages of SCN infection across different soybean varieties; however, its role in the mechanism and function of SCN tolerance remains unclear. This study utilized bioinformatics prediction and qRT-PCR validation to elucidate the initial response of miR862b to SCN and screen its target genes, including GmGRX1 (Glyma.14G057300). Functional validation was conducted using K599-induced transgenic soybean roots, further indicating that overexpressing pre-miR862b positively regulates soybean resistance to SCN while significantly suppressing the expression of its target gene GmGRX1. Conversely, transgenic lines with tandem repeats silencing miR862b exhibited reduced SCN resistance, accompanied by upregulated expression levels of the target gene GmGRX1. In addition, treatment with artificially synthesized ds-miR862b in soybeans inhibited SCN infection in roots while also moderately suppressing seed germination and seedling development. In summary, these findings provide a theoretical basis for elucidating the function of miR862b and its target gene GmGRX1 in regulating soybean resistance to SCN.