Glutathionylation-mediated degradation of a cap-binding protein enhances Arabidopsis resistance to Plutella xylostella.

The lepidopteran insect pest diamondback moth (Plutella xylostella) causes severe yield losses in cruciferous plants worldwide; therefore, there is an urgent need to characterize the genes for resistance to P. xylostella in plants and decipher their mechanisms. We previously demonstrated that inactivating NOVEL CAP-BINDING PROTEIN (NCBP), also known as RESISTANCE TO PLUTELLA XYLOSTELLA (RPX1), enhanced Arabidopsis (Arabidopsis thaliana) resistance to P. xylostella larvae, and the larval infestation caused NCBP degradation. Here, we report that MYB30-INTERACTING WD40 PROTEIN 1 (MIW1), a component of the Cul4-RING ubiquitin ligase complex, interacts with NCBP and causes its degradation through the 26S proteasome pathway. Protein interaction, degradation, and site mutagenesis assays of NCBP indicate that the glutathione transferase GSTF2 also interacts with NCBP and promotes its glutathionylation, ubiquitination, and degradation. GSTF2 and glutathionylation of NCBP enhance the interaction between MIW1 and NCBP. Moreover, consistent with the roles of GSTF2 and MIW1 in P. xylostella resistance, gstf2 and miw1 mutants were sensitive to larval infestation, whereas transgenic Arabidopsis overexpressing GSTF2 and MIW1 were more resistant to the larvae. These findings demonstrate a role for glutathionylation in regulating 26S proteasome-mediated protein degradation in plant resistance to insect pests, thus revealing the functional mechanism of NCBP in this process.