Degradation of AtSRC2 by SKP1/BTB/POZ domain effectors in Heterodera schachtii inhibits RBOHF via ROS and enhances infection.

Upon pathogen infection, plants trigger a reactive oxygen species (ROS) burst to activate immunity. Although some effectors secreted by plant-parasitic nematodes are known to suppress ROS-mediated immunity, there are limited studies examining the regulation of respiratory burst oxidase homologs (RBOH)-dependent ROS pathways by these nematodes. Using developmental expression analysis, in situ hybridization, and immunohistochemical tests, we found that both Hs28B03 and Hs8H07 were expressed and secreted during the early parasitism by Heterodera schachii. Transgenic Arabidopsis plants were used to assess the role of Hs28B03 and Hs8H07 in H. schachii parasitism. Yeast two-hybrid was used to identify host targets in Arabidopsis. We identified Hs28B03 and Hs8H07 from H. schachtii, which play a crucial role in promoting nematode infection and parasitism, as well as inhibiting host immune responses. Hs28B03 and Hs8H07 harbor the SKP1/BTB/POZ domain and exhibit the capacity to mimic the host's SKP1 proteins, allowing them to regulate the ubiquitin pathway within the plant. Hs28B03 and Hs8H07 specifically target and degrade the host's AtSRC2 protein, inhibiting the Ca-dependent production of ROS mediated by RBOHF, enhancing Arabidopsis susceptibility to H. schachtii. In conclusion, nematodes can secrete effectors that mimic plant ubiquitination pathway components, suppressing ROS bursts via the RBOHF pathway, thereby facilitating parasitism.