Ubiquitin-conjugated degradation of golden 2-like transcription factor is mediated by CUL4- DDB1-based E3 ligase complex in tomato.

CULLIN4- RING ubiquitin ligases ( CRL4s) as well as their targets are fundamental regulators functioning in many key developmental and stress responses in eukaryotes. In tomato ( Solanum lycopersicum), molecular cloning has revealed that the underlying genes of natural spontaneous mutations high pigment 1 ( hp1), high pigment 2 ( hp2) and uniform ripening ( u) encode UV- DAMAGED DNA BINDING PROTEIN 1 ( DDB1), DE- ETIOLATED 1 ( DET1) and GOLDEN 2- LIKE ( GLK2), respectively. However, the molecular basis of the opposite actions of tomato GLK2 vs CUL4- DDB1- DET1 complex on regulating plastid level and fruit quality remains unknown., Here, we provide molecular evidence showing that the tomato GLK2 protein is a substrate of the CUL4- DDB1- DET1 ubiquitin ligase complex for the proteasome degradation., Sl GLK2 is degraded by the ubiquitin-proteasome system, which is mainly determined by two lysine residues (K11 and K253). Sl GLK2 associates with the CUL4- DDB1- DET1 E3 complex in plant cells. Genetically impairing CUL4, DDB1 or DET1 results in a retardation of Sl GLK2 degradation by the 26S proteasome., These findings are relevant to the potential of nutrient accumulation in tomato fruit by mediating the plastid level and contribute to a deeper understanding of an important regulatory loop, linking protein turnover to gene regulation. [ABSTRACT FROM AUTHOR]