Regulation of fruit ripening by the brassinosteroid biosynthetic gene SlCYP90B3 via an ethylene-dependent pathway in tomato

Songshen Hu,Changqing Zhu,Wenyi Duan,Qiaomei Wang,Haoran Liu,Shuo Li,Lihong Liu,Zhiyong Shao,Tao Xu,Fanliang Meng,Dongyi Liang

doi:10.1038/s41438-020-00383-0

Songshen Hu, Changqing Zhu + Show 9 more

Open Access

https://doi.org/10.1038/s41438-020-00383-0

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Journal: Horticulture Research	Publication Date: Oct 1, 2020
Citations: 42	License type: open-access

Affiliation: Zhejiang University

Abstract

The essential role of ethylene in fruit ripening has been thoroughly studied. However, the involvement of brassinosteroids (BRs) in the regulation of fruit ripening and their relationship with the ethylene pathway are poorly understood. In the current study, we found that BRs were actively synthesized during tomato fruit ripening. We then generated transgenic lines overexpressing or silencing SlCYP90B3, which encodes a cytochrome P450 monooxygenase that catalyzes the rate-limiting step of BR synthesis. The expression level of SlCYP90B3 was positively related to the contents of bioactive BRs as well as the ripening process in tomato fruit, including enhanced softening and increased soluble sugar and flavor volatile contents. Both carotenoid accumulation and ethylene production were strongly correlated with the expression level of SlCYP90B3, corroborated by the altered expression of carotenoid biosynthetic genes as well as ethylene pathway genes in transgenic tomato fruits. However, the application of the ethylene perception inhibitor 1-methycyclopropene (1-MCP) abolished the promotion effect of SlCYP90B3 overexpression on carotenoid accumulation. Taken together, these results increase our understanding of the involvement of SlCYP90B3 in bioactive BR biosynthesis as well as fruit ripening in tomato, thus making SlCYP90B3 a target gene for improvement of visual, nutritional and flavor qualities of tomato fruits with no yield penalty.

Highlights

Tomato (Solanum lycopersicum), an important agricultural crop species, is a model system for studying fruit development and ripening
Fruit ripening in tomato is coordinated with brightened appearance caused by pigment accumulation; texture changes caused by tissue softening; and nutrient and flavor improvement through the bioactive compound, sugar, acid, and volatile organic compound (VOC) metabolism
We examined the expression levels of BR biosynthetic genes (SlCYP90B3, SlCPD, SlDWARF) and catabolic genes (SlCYP734A7) during tomato fruit ripening (Fig. 1a)

Summary

Introduction

Tomato (Solanum lycopersicum), an important agricultural crop species, is a model system for studying fruit development and ripening. The fruit ripening process, carotenoid accumulation, and ethylene production were found to be modulated by the SlCYP90B3 expression level. We examined the expression levels of BR biosynthetic genes (SlCYP90B3, SlCPD, SlDWARF) and catabolic genes (SlCYP734A7) during tomato fruit ripening (Fig. 1a).

Results

Conclusion