J Integr Plant Biol. ›› 2023, Vol. 65 ›› Issue (5): 1277-1296.DOI: 10.1111/jipb.13444

• Molecular Physiology • Previous Articles     Next Articles

The safflower MBW complex regulates HYSA accumulation through degradation by the E3 ligase CtBB1

Yingqi Hong1,2, Yanxi Lv1, Jianyi Zhang1, Naveed Ahmad1,3, Xiaokun Li4,5, Na Yao1*, Xiuming Liu1,4,5* and Haiyan Li2*   

  1. 1. College of Life Sciences, Engineering Research Center of the Chinese Ministry of Education for Bioreactor and Pharmaceutical Development, Jilin Agricultural University, Changchun 130118, China;
    2. College of Tropical Crops, Hainan University, Haikou 570100, China;
    3. Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghaijiaotong University, Shanghai 200240, China;
    4. Institute of Life Sciences, Wenzhou Medical University, Wenzhou 325000, China;
    5. Biomedical Collaborative Innovation Center of Zhejiang Province, Wenzhou Medical University, Wenzhou 325000, China
    *Correspondences: Na Yao (yaona1103@126.com; Dr. Yao is fully responsible for the distributions of all materials associated with this article); Xiuming Liu (xiuming1211@163.com); Haiyan Li (hyli99@163.com)
  • Received:2022-09-07 Accepted:2023-01-03 Online:2023-03-27 Published:2023-05-01

Abstract: The regulatory mechanism of the MBW (MYB‐ bHLH‐WD40) complex in safflower (Carthamus tinctorius) remains unclear. In the present study, we show that the separate overexpression of the genes CtbHLH41, CtMYB63, and CtWD40‐6 in Arabidopsis thaliana increased anthocyanin and procyanidin contents in the transgenic plants and partially rescued the trichome reduction phenotype of the corresponding bhlh41, myb63, and wd40‐6 single mutants. Overexpression of CtbHLH41, CtMYB63, or CtWD40‐6 in safflower significantly increased the content of the natural pigment hydroxysafflor yellow A (HYSA) and negatively regulated safflower petal size. Yeast‐two‐hybrid, functional, and genetic assays demonstrated that the safflower E3 ligase CtBB1 (BIG BROTHER 1) can ubiquitinate CtbHLH41, marking it for degradation through the 26S proteasome and negatively regulating flavonoid accumulation. CtMYB63/CtWD40‐6 enhanced the transcriptional activity of CtbHLH41 on the CtDFR (dihydroflavonol 4‐reductase) promoter. We propose that the MBW‐CtBB1 regulatory module may play an important role in coordinating HYSA accumulation with other response mechanisms.

Key words: CtBB1, hydroxysafflor yellow A, MBW, safflower, ubiquitination

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