The protein quality control system manages plant defence compound synthesis

Plants defend themselves against attackers by producing bioactive secondary metabolites such as triterpene saponins; here, the endoplasmic-reticulum-associated degradation (ERAD) system is shown to control the activity of HMGR, the rate-limiting enzyme in the supply of the terpene precursor isopentenyl diphosphate, thereby preventing unrestrained saponin production and ensuring the integrity of plant development.