Regulation of fruit ripening by the brassinosteroid biosynthetic gene SlCYP90B3 via an ethylene-dependent pathway in tomato
Hu, S.; Liu, L.; Li, S.; Shao, Z.; Meng, F.; Liu, H.; Duan, W.; Liang, D.; Zhu, C.; Xu, T.; Wang, Q.
Horticulture Research 7: 163
ISSN/ISBN: 2052-7276 PMID: 33082970 DOI: 10.1038/s41438-020-00383-0
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 silencingSlCYP90B3, which encodes a cytochrome P450 monooxygenase that catalyzes the rate-limiting step of BR synthesis. The expression level ofSlCYP90B3was 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 ofSlCYP90B3, 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 ofSlCYP90B3overexpression on carotenoid accumulation. Taken together, these results increase our understanding of the involvement ofSlCYP90B3in bioactive BR biosynthesis as well as fruit ripening in tomato, thus makingSlCYP90B3a target gene for improvement of visual, nutritional and flavor qualities of tomato fruits with no yield penalty.