J Integr Plant Biol.

• Research Article •    

The CsphyB–CsPIF4–CsBRC1 module regulates ABA biosynthesis and axillary bud outgrowth in cucumber

Ye Liu1, Zhihan Liu1, Chuang Li1, Min Li1, Daixi She1, Jiahao Zhang1, Huiqi Ren1, Xitong Zhong1, Yafei Huang1, Yuxiang Huang1, Yuting He1, Yuan Liu1, Jiacai Chen1, Yan Geng1, Xiaoli Li2, Kailiang Bo3, Yiqun Weng4,5, Xiaolan Zhang1* and Jianyu Zhao1*   

  1. 1. Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetable Sciences, China Agricultural University, Beijing 100193, China
    2. College of Horticulture Science and Technology, Hebei Normal University of Science and Technology, Qinhuangdao 066004, China
    3. State Key Laboratory of Vegetable Biobreeding, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
    4. Department of Plant and Agroecosystem Science, University of Wisconsin, Madison, WI 53706, USA
    5. USDA‐ARS Vegetable Crops Research Unit, Madison, WI 53705, USA

    *Correspondences: Xiaolan Zhang (zhxiaolan@cau.edu.cn); Jianyu Zhao (zhaojianyu@cau.edu.cn, Dr. Zhao is fully responsible for the distributions of all materials associated with this article)
  • Received:2024-03-15 Accepted:2025-05-17 Online:2025-06-12
  • Supported by:
    This work is supported by grants from the National Natural Science Foundation of China (32372699, 32025033, and 32102387), Key R&D Program of Shandong Province, China (2024LZGCQY006), and S&T Program of Hebei (22326308D).

Abstract: Shoot branching is an important crop agronomic trait that directly affects plant architecture and crop productivity. Although phytochrome B (phyB), BRANCHED1 (BRC1), and abscisic acid (ABA) mediate axillary bud outgrowth, it is unknown if there is any integrating factor among them in the Plantae. We report that mutation of CsphyB or inactivation of CsphyB by shade inhibits lateral bud outgrowth in cucumber. Cucumber PHYTOCHROME INTERACTING FACTOR 4 (CsPIF4) interacts with CsphyB and directly binds to the promoter of CsBRC1 to activate CsBRC1 expression. CsBRC1 also directly promotes the expression of ABA biosynthesis gene 9-CIS-EPOXICAROTENOID DIOXIGENASE 3 (CsNCED3). Functional disruption of CsPIF4 decreased expression of CsBRC1 and CsNCED3, reduced ABA accumulation, and increased bud outgrowth in cucumber. Csnced3 mutants had reduced ABA levels and increased lateral bud outgrowth. These results suggest that a regulatory network involving CsphyB-CsPIF4-CsBRC1 exists that integrates light signaling and ABA biosynthesis to modulate bud outgrowth. This provides a strategy to manipulate branch numbers in crop breeding to realize ideal branching characteristics to maximize yield.

Key words: ABA, axillary bud outgrowth, CsBRC1, CsphyB, CsPIF4, cucumber

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