J Integr Plant Biol. ›› 2023, Vol. 65 ›› Issue (7): 1794-1813.DOI: 10.1111/jipb.13491

• Molecular Physiology • Previous Articles     Next Articles

The brassinosteroid signaling component SlBZR1 promotes tomato fruit ripening and carotenoid accumulation

Fanliang Meng1†, Haoran Liu1†, Songshen Hu1, Chengguo Jia2, Min Zhang1, Songwen Li1, Yuanyuan Li1, Jiayao Lin1, Yue Jian1, Mengyu Wang1, Zhiyong Shao1, Yuanyu Mao1, Lihong Liu1* and Qiaomei Wang1*   

  1. 1. Key Laboratory of Horticultural Plant Growth and Development, Ministry of Agriculture, Department of Horticulture, Zhejiang University, Hangzhou 310058, China;
    2. College of Plant Science, Jilin University, Changchun 130062, China
    These authors contributed equally to this work.
    *Correspondences: Qiaomei Wang (qmwang@zju.edu.cn, Dr. Wang is fully responsible for the distributions of the materials associated with this article); Lihong Liu (liulihong@zju.edu.cn)
  • Received:2022-12-05 Accepted:2023-03-31 Online:2023-04-03 Published:2023-07-01

Abstract: The plant hormone ethylene is essential for climacteric fruit ripening, although it is unclear how other phytohormones and their interactions with ethylene might affect fruit ripening. Here, we explored how brassinosteroids (BRs) regulate fruit ripening in tomato (Solanum lycopersicum) and how they interact with ethylene. Exogenous BR treatment and increased endogenous BR contents in tomato plants overexpressing the BR biosynthetic gene SlCYP90B3 promoted ethylene production and fruit ripening. Genetic analysis indicated that the BR signaling regulators Brassinazole-resistant1 (SlBZR1) and BRI1-EMS-suppressor1 (SlBES1) act redundantly in fruit softening. Knocking out SlBZR1 inhibited ripening through transcriptome reprogramming at the onset of ripening. Combined transcriptome deep sequencing and chromatin immunoprecipitation followed by sequencing identified 73 SlBZR1-repressed targets and 203 SlBZR1-induced targets involving major ripening-related genes, suggesting that SlBZR1 positively regulates tomato fruit ripening. SlBZR1 directly targeted several ethylene and carotenoid biosynthetic genes to contribute to the ethylene burst and carotenoid accumulation to ensure normal ripening and quality formation. Furthermore, knock-out of Brassinosteroid-insensitive2 (SlBIN2), a negative regulator of BR signaling upstream of SlBZR1, promoted fruit ripening and carotenoid accumulation. Taken together, our results highlight the role of SlBZR1 as a master regulator of tomato fruit ripening with potential for tomato quality improvement and carotenoid biofortification.

Key words: brassinosteroids, carotenoids, ethylene, fruit ripening, quality improvement, SlBIN2, SlBZR1, tomato

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