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A tomato B‐box protein Sl BBX 20 modulates carotenoid biosynthesis by directly activating PHYTOENE SYNTHASE 1 , and is targeted for 26S proteasome‐mediated degradation
Author(s) -
Xiong Cheng,
Luo Dan,
Lin Aihua,
Zhang Chunli,
Shan Libo,
He Ping,
Li Bo,
Zhang Qiaomei,
Hua Bin,
Yuan Zilv,
Li Hanxia,
Zhang Junhong,
Yang Changxian,
Lu Yongen,
Ye Zhibiao,
Wang Taotao
Publication year - 2019
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.15373
Subject(s) - phytoene , phytoene synthase , carotenoid , biochemistry , ubiquitin ligase , biology , proteasome , ubiquitin , phytoene desaturase , biosynthesis , lycopene , repressor , transcription factor , f box protein , microbiology and biotechnology , enzyme , gene
Summary Carotenoids play important roles in many biological processes, such as light harvesting, photoprotection and visual attraction in plants. However, the regulation of carotenoid biosynthesis is still not fully understood. Here, we demonstrate that Sl BBX 20, a B‐box ( BBX ) zinc‐finger transcription factor, is a positive regulator of carotenoid accumulation in tomato ( Solanum lycopersicum ). Overexpression of Sl BBX 20 leads to dark green fruits and leaves and higher levels of carotenoids relative to the wild‐type. Interactions between Sl BBX 20 and DE ‐ ETIOLATED 1 ( Sl DET 1) lead to the ubiquitination and 26S proteasome‐mediated degradation of Sl BBX 20. Moreover, deficiencies in the components of the CUL 4‐ DDB 1‐ DET 1 complex enhanced the stability of the Sl BBX 20 protein. Thus, we conclude that Sl BBX 20 is a substrate of the CUL 4‐ DDB 1‐ DET 1 E3 ligase. Sl BBX 20 can activate the expression of PHYTOENE SYNTHASE 1 , encoding a key enzyme in carotenoid biosynthesis, by directly binding to a G‐box motif in its promoter, which results in the elevated levels of carotenoids in Sl BBX 20 overexpression lines. We identified a key regulator of carotenoid biosynthesis and demonstrated that the stability of Sl BBX 20 is regulated by ubiquitination. These findings provide us a new target for the genetic improvement of the nutritional quality of tomato fruit.