Sugar-inducible RPT2a, a subunit of 26S proteasome, participates in sugar response in Arabidopsis

抄録

The ubiquitin/26S proteasome system (UPS) plays a central role in the degradation of short-lived regulatory proteins that control many cellular events. In this study, the Arabidopsis knockout mutant rpt2a, which contains a defect in the AtRPT2a subunit of the 26S proteasome regulatory particle, showed hypersensitivity to sugars as well as enlarged leaves. When the role of RPT2a in sugar response was examined in further detail it was found that putatively only the AtRPT2a gene of 19S proteasome was markedly transcriptionally promoted by sugar application. Notably, poly-ubiquitinated proteins degraded by the UPS accumulated significantly in rpt2a mutant under 6% sucrose conditions compared to wild type. In addition, the AtRPT2a gene in gin2, a glucose insensitive mutant with a defective glucose-sensing hexokinase, was not upregulated by sugar application, indicating that AtRPT2a is involved in hexokinase-dependent sugar response. Taken together, the above findings indicate that AtRPT2a plays an essential role in the maintenance of proteasome-dependent proteolysis activity in response to sugars.