MiR398b Targets Superoxide Dismutase Genes in Soybean in Defense Against Heterodera glycines via Modulating ROS Homeostasis

MicroRNAs (miRNAs) play crucial roles in plant defense responses. However, the underlying mechanism by which miR398b contributes to soybean responses to soybean cyst nematode (SCN, Heterodera glycines) remains elusive. In this study, by using Agrobacterium rhizogenes-mediated transformation of soybean hairy roots, we observed that miR398b and target genes GmCCS and GmCSD1b played vital functions in soybean-H. glycines interaction. The study revealed that the abundance of miR398b was down-regulated by H. glycines infection, and overexpression miR398b enhanced susceptibility of soybean to H. glycines. Conversely, silencing of miR398b improved soybean resistance to H. glycines. Detection assays revealed that miR398b rapidly senses stress-induced ROS, leading to the repression of target genes GmCCS and GmCSD1b, and regulating the accumulation of plant defense genes against nematodes infection. Moreover, exogenous synthetic ds-miR398b enhanced soybean sensitivity to H. glycines by modulating H 2 O 2 and O 2 – levels. Functional analysis demonstrated that overexpression GmCCS and GmCSD1b in soybean enhanced resistance to H. glycines. RNA interference (RNAi)-mediated repression of GmCCS and GmCSD1b in soybean increased susceptibility to H. glycines. RNA-sequencing revealed that a majority of differentially expressed genes (DEGs) in overexpression GmCCS were associated with oxidative stress. Overall, the results indicate that miR398b targets superoxide dismutase genes, which negatively regulate soybean resistance to H. glycines via modulating ROS levels and defense signal.