Cuticular wax plays crucial roles in protecting plants from environmental stresses， particularly drought stress. Many enzyme-encoding genes and transcription factors involved in wax biosynthesis have been identified， but the underlying posttranslational regulatory mechanisms are poorly understood. Here， we demonstrate that ()， encoding a Really Interesting New Gene (RING)-type protein， is a critical regulator of wax biosynthesis in rice (). The cuticular wax contents were significantly reduced in overexpression plants but increased in mutants compared with the wild type， which resulted in a response opposite that of drought stress. DHS exhibited E3 ubiquitin ligase activity and interacted with th... More
Cuticular wax plays crucial roles in protecting plants from environmental stresses， particularly drought stress. Many enzyme-encoding genes and transcription factors involved in wax biosynthesis have been identified， but the underlying posttranslational regulatory mechanisms are poorly understood. Here， we demonstrate that ()， encoding a Really Interesting New Gene (RING)-type protein， is a critical regulator of wax biosynthesis in rice (). The cuticular wax contents were significantly reduced in overexpression plants but increased in mutants compared with the wild type， which resulted in a response opposite that of drought stress. DHS exhibited E3 ubiquitin ligase activity and interacted with the homeodomain-leucine zipper IV protein ROC4. Analysis of overexpression plants and mutants indicated that ROC4 positively regulates cuticular wax biosynthesis and the drought stress response. ROC4 is ubiquitinated in vivo and subjected to ubiquitin/26S proteasome-mediated degradation. ROC4 degradation was promoted by DHS but delayed in mutants. ROC4 acts downstream of DHS， and Os is a direct downstream target of the DHS-ROC4 cascade. These results suggest a mechanism whereby DHS negatively regulates wax biosynthesis by promoting the degradation of ROC4， and they suggest that DHS and ROC4 are valuable targets for the engineering of drought-tolerant rice cultivars.
