Ubiquitin‐conjugated degradation of golden 2‐like transcription factor is mediated by CUL 4‐ DDB 1‐based E 3 ligase complex in tomato

• Published in: The New phytologist Vol. 209; no. 3; pp. 1028 - 1039
• Main Authors: Tang, Xiaofeng, Miao, Min, Niu, Xiangli, Zhang, Danfeng, Cao, Xulv, Jin, Xichen, Zhu, Yunye, Fan, Youhong, Wang, Hongtao, Liu, Ying, Sui, Yuan, Wang, Wenjie, Wang, Anquan, Xiao, Fangming, Giovannoni, Jim, Liu, Yongsheng
• Format: Journal Article
• Language: English
• Published: 01.02.2016
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.13635

Summary CULLIN 4‐ RING ubiquitin ligases ( CRL 4s) 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 ( DDB 1), DE ‐ ETIOLATED 1 ( DET 1) and GOLDEN 2‐ LIKE ( GLK 2), respectively. However, the molecular basis of the opposite actions of tomato GLK 2 vs CUL 4‐ DDB 1‐ DET 1 complex on regulating plastid level and fruit quality remains unknown. Here, we provide molecular evidence showing that the tomato GLK 2 protein is a substrate of the CUL 4‐ DDB 1‐ DET 1 ubiquitin ligase complex for the proteasome degradation. Sl GLK 2 is degraded by the ubiquitin‐proteasome system, which is mainly determined by two lysine residues (K11 and K253). Sl GLK 2 associates with the CUL 4‐ DDB 1‐ DET 1 E3 complex in plant cells. Genetically impairing CUL 4 , DDB 1 or DET 1 results in a retardation of Sl GLK 2 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.