ABSTRACT Rhg1 mediates soybean resistance to soybean cyst nematode. Glyma.18G022400 , one of three resistance-conferring genes at the complex Rhg1 locus, encodes the putative amino acid transporter AAT Rhg1 whose mode of action is largely unknown. We discovered that AAT Rhg1 protein abundance increases 7- to 15-fold throughout root cells penetrated by SCN. These root cells develop increased abundance of vesicles and larger vesicle-like bodies. AAT Rhg1 was often associated with these vesicles. AAT Rhg1 abundance remained low in syncytia (plant reprogrammed feeding cells), unlike the Rhg1 α-SNAP protein whose abundance was previously shown to increase in syncytia. In N. benthamiana , if soybean AAT Rhg1 was present, oxidative stress promoted formation of larger macrovesicles and they contained AAT Rhg1 . AAT Rhg1 was found to interact with GmRBOHC2, a soybean ortholog of Arabidopsis RBOHD previously found to exhibit upregulated expression upon SCN infection. Reactive oxygen species (ROS) generation was more elevated when AAT Rhg1 and GmRBOHC2 abundance were co-expressed. These findings suggest that AAT Rhg1 contributes to SCN resistance along the penetration path as SCN invades the plant, and does so at least in part by interactions with GmRBOHC2 that increase ROS production. The study also shows that Rhg1 resistance functions via at least two spatially and temporally separate modes of action.

The soybean Rhg1 amino acid transporter protein becomes abundant along the SCN penetration path and impacts ROS generation