Vacuolar protein sorting 29 (VPS29) is a pivotal component of the retromer complex, which plays a central role in endosomal trafficking. Numerous studies have investigated its functions in various eukaryotic systems; however, research in plants is still at an early stage. Moreover, the mechanisms controlling its abundance and stability remain largely unknown. In this study, we elucidated the role of constitutive photomorphogenic 1 (COP1) in regulating the abundance of Arabidopsis VPS29 (AtVPS29), a component of the trimeric retromer complex. Degradation of AtVPS29 is delayed by treatment with the proteasome inhibitor MG132, resulting in the accumulation of ubiquitinated AtVPS29 in MG132-treated plants. The AtVPS29 level is higher in cop1-6 mutant seedlings than in wild-type seedlings under both continuous light and dark conditions. In addition, AtVPS29 abundance is reduced in COP1-overexpressing plants compared with wild-type plants. Furthermore, COP1 directly interacts with AtVPS29, and AtVPS29 is ubiquitinated by the E3 ligase activity of COP1. Moreover, genes encoding the trimeric retromer complex components AtVPS35a and AtVPS26a are upregulated in cop1-6 mutants. Together, our data indicate that COP1 negatively regulates the abundance and stability of AtVPS29 through its E3 ligase activity and suggest that COP1 is involved in regulating the function of the trimeric retromer complex.
Min et al. (Sat,) studied this question.