Transcriptional and Functional Insights into <i>GmPUB33A</i>-Mediated Regulation of Soybean Resistance to Soybean Cyst Nematode

Ubiquitination-related genes are pivotal in modulating plant responses to biotic stress. The U-box E3 ubiquitin ligase gene <i>GmPUB33A</i> has been identified as a negative regulator of resistance to soybean cyst nematode (SCN). To elucidate the underlying molecular mechanisms, we conducted high-throughput sequencing and transcriptome analyses on <i>GmPUB33A</i>-overexpression and -RNAi transgenic hairy roots. Three differentially expressed genes (DEGs) were silenced using siRNA for functional validation. Compared with empty vector control, 11,088 DEGs were identified. Gene Ontology (GO) and KEGG analyses revealed these DEGs were significantly enriched in defense responses, oxidative stress, phenylpropanoid biosynthesis, and MAPK signaling. Functional analysis revealed that silencing <i>Glyma.07G061500</i> and <i>Glyma.19G258700</i> reduced the number of nematodes by 32.62% and 19.34%, respectively. Furthermore, β-glucuronidase (GUS) activity and reactive oxygen species (ROS) assays demonstrated their involvement in SCN parasitism and ROS accumulation. These findings provide novel insights into <i>GmPUB33A</i>-mediated SCN susceptibility in soybean.